To check your server info, do lscpu 
To run a bash script without executing it, do bash -n scriptname.sh 
To see help commands do command --help or man command. To paste into PuTTY, use SHIFT + INSERT. 
For detailed software and hardware info do apt-get install hardinfo then hardinfo. For CentOS 6 use [http://pkgs.repoforge.org/hardinfo/hardinfo-0.5.1-1.el6.rf.x86_64.rpm this]. 
To write to a user in the same SSH server, do w, get their tty session and then do write user ttySession. If they are root, do write root Session 
[http://www.linuxfocus.org/English/September1999/article103.html Awk introduction], [http://tldp.org/LDP/Bash-Beginners-Guide/html/sect_07_01.html If manual].

== Append date to same line ==

Either of these will work:

<pre>| awk '{ print strftime("%Y-%m-%d %H:%M:%S"), $0; }'
| ts '%F %T'</pre>

To customise date, put a + symbol in front of the flag:

<pre>date +%R
14:32</pre>

To get this format of the date/time:

24 May 2013 10:25:33

Use:

<pre>date +%d\ %B\ %Y\ %H:%M:%S</pre>

== authorized_keys (RSA) ==

This will show you how to SCP, SSH and rSync without prompting for password between two servers.

Whenever you need to use SCP to copy files, it asks for passwords. Same with rSync as it (by default) uses SSH as well. Usually SCP and rSync commands are used to transfer or backup files between known hosts or by the same user on both the hosts. It can get really annoying the password is asked every time. I even had the idea of writing an expect script to provide the password. Of course, I didn't. Instead I browsed for a solution and found it after quite some time. There are already a couple of links out there which talk about it. I am adding to it...

Lets say you want to copy between two hosts host_src and host_dest. host_src is the host where you would run the SCP, SSH or rSync command, irrespective of the direction of the file copy!

On host_src, run this command as the user that runs SCP/SSH/rSync

<pre>ssh-keygen -t rsa</pre>

This will prompt for a passphrase. Just press the enter key. It'll then generate an identification (private key) and a public key. Do not ever share the private key with anyone! ssh-keygen shows where it saved the public key. This is by default ~/.ssh/id_rsa.pub:

Your public key has been saved in <your_home_dir>/.ssh/id_rsa.pub

Transfer the id_rsa.pub file to host_dest by either FTP, SCP, rSync or any other method.

On host_dest, '''login as the remote user which you plan to use when you run SCP, SSH or rSync on host_src'''.

Make sure the folder ~/.ssh exists first, if not do:

<pre>mkdir ~/.ssh</pre>

Copy the contents of id_rsa.pub to ~/.ssh/authorized_keys

<pre>cat id_rsa.pub >>~/.ssh/authorized_keys
chmod 700 ~/.ssh/authorized_keys</pre>

If this file does not exists, then the above command will create it. Make sure you remove permission for others to read this file. If its a public key, why prevent others from reading this file? Probably, the owner of the key has distributed it to a few trusted users and has not placed any additional security measures to check if its really a trusted user.

Note that SSH by default does not allow root to log in. This has to be explicitly enabled on host_dest. This can be done by editing /etc/ssh/sshd_config and changing the option of PermitRootLogin from no to yes. Don't forget to restart SSHD so that it reads the modified config file. Do this only if you want to use the root login.

Well, thats it. Now you can run SCP, SSH and rSync on host_src connecting to host_dest and it won't prompt for the password. Note that this will still prompt for the password if you are running the commands on host_dest connecting to host_src. You can reverse the steps above (generate the public key on host_dest and copy it to host_src) and you have a two way setup ready!

== .bashrc ==

<pre>vim /root/.bashrc</pre>

=== Colours ===

https://wiki.archlinux.org/index.php/Color_Bash_Prompt

Add these:

<pre>alias ls='ls --color=auto'
alias grep='grep --color=auto'</pre>

<pre>source /root/.bashrc</pre>

<pre>vim /root/.vimrc</pre>
<pre>syntax on</pre>

Exit your session and re-enter it.

=== Crontab editor ===

Add this line in:

<pre>EDITOR=vim; export EDITOR</pre>

<pre>crontab -e</pre>

== Binary/binaries ==

These are normally in the bin or sbin folder for a program.

== Calendar ==

<pre>apt-get install gcal
gcal -K -q GB_EN December/2012-January/2013 # Holidays for Dec/2012 and Jan/2013 with week numbers</pre>

Credit to User [http://www.commandlinefu.com/commands/by/mpb MPB]

== Check Linux version/kernel ==

cat /etc/issue

For Ubuntu do cat /etc/issue or for some CentOS distributions use cat /etc/redhat-release

<pre>uname -a
uname -r #for just the kernel
uname -rs #for OS and kernel</pre>

== Check if SELinux is enabled ==

<pre>apt-get install chkconfig
yum install chkconfig

chkconfig --list
cat /etc/sysconfig/selinux
sestatus
selinuxenabled</pre>

== Check if Virtualization is available for server ==

CentOS:

<pre>egrep '(vmx|svm)' --color=always /proc/cpuinfo</pre>

Ubuntu:

<pre>apt-get install cpu-checker
kvm-ok</pre>

== Check your PuTTY (TTY) session ==

Type this into command line:

tty

== CLI/bash Commands and scripting ==

* [http://www.cyberciti.biz/faq/unix-linux-bsd-appleosx-bash-assign-variable-command-output Assign variable command output]

* For variables with multiple pipes "|", use tacs `` instead of quotes ""
* If you are attempting to use the Unix mail function, you have to specify a body otherwise it will hang.
* If you have an if statement and its requirements are not met (e.g. greater than) and it then moves onto the next if statement, if it uses a mail function it may send it to the root user's email or the Admin/Administrator's email address. To avoid this use > /dev/null . 2>&1 likely won't work.
* It seems if you are using the read function, you can only call a variable that is inside of it (subshell), from [http://www.unixguide.net/unix/bash/E4.shtml here].
* To stop a ping after x amount of responses, do ping -c x or use ping -oc y (where y equals a maximum amount of tries)
* Use >> to append an output to the end of the file.
* The use of && means that you only echo the name of the directory if the directory creation is successful.

- The $() syntax allows you to load anything echoed to STDOUT to be loaded into a variable, and the single quotes ensure that if there are any spaces in the directory name, it still gets loaded into a single variable. To use command substitution, enclose any command that generates output to standard output inside parentheses and precede the opening parenthesis with a dollar sign, $(command). Command substitution is useful when assigning a value to a variable. It is handy for using the output of one command as an argument to another command. [http://mywiki.wooledge.org/BashFAQ/082 Why is $(...) preferred over `...` (backticks)?] . A good use of this is in http://serverkb.co.uk/tools/slow.sh

* To quote double quotes (") do the following: echo -e "Testing \"quotes\" here" - this will show as Testing "quotes"
* Quotes prevent wildcard (*) expansion.

=== $? ===

This is the exit status/code of the last executed function/program/command.

=== [http://beyondgrep.com ack] ===

To look into.

=== [http://www.grymoire.com/Unix/Awk.html Awk] ===

To '''print out a list of just folders/file'''s you want, do;

<pre>ls -l filepath | awk '{print $9;}'</pre>

This won't work correctly if there is spaces in the filename. To resolve this, use [[Linux#Find | this]] command whilst in the directory itself.

To do multiple sections of a result, do:

awk '{print $1,$2,$4,$X;}'

If you want to '''get rid of/cut certain/specific lines/rows from STDOUT''' aka '''print a specific line''', use awk in this way:

<pre>awk 'NR==22'</pre>

This is for use ''without'' a file. This example will only display the 22nd row from your output.

Notes: Blank lines count as a row. To do multiple lines do awk 'NR==22,NR==25' . This will output line 22-25.

The command sed '22 ! d' would do the same as the awk 'NR==22' example.

To '''get rid of pipe symbols in a file''', do:

awk -F'|' '{print $1,$10}' FileWithPipes > FileWithoutPipes

Alternatively if you get a list, e.g of domains from MySQL with only one column selected, put them in a file and you can remove the pipes by doing:

<pre>cat domainlist | awk '{print $2}' > list</pre>

awk '{ printf "%-20s %-40s\n", $1, $2}' allows you to '''[http://stackoverflow.com/questions/6462894/how-can-i-format-the-output-of-a-bash-command-in-neat-columns print information in columns]'''

=== Cat ===

Parse JSON file:

<pre>cat file | python .mjson.tool</pre>

=== Cut ===

This tool can be used in an example where you get an output but want to strip it to exactly what you need e.g.

lookupipscript.sh <IPaddress>

Output below:

<pre>Plan : Bronze, Silver, Gold
Type : IPv4 or IPv6
URL : http
IP : 0.0.0.0(primary)</pre>

lookupipscript.sh <IPaddress> | sed 'row ! d' | awk '{print $column;}'

This would output 0.0.0.0(primary). To get just the IP address and not the "(primary)" section, do:

| cut -c 1-7

Cut counts the first number/letter as 1, not 0.

=== eval ===

Use this of you want run a variable after a pipe and to shorten down your scripts. e.g. in http://serverkb.co.uk/tools/getdns.sh

<pre>ns="ns.nameserver.co.uk"
d="domain.co.uk"
g="grep $d | grep -v 'DiG\|;'"

echo "dig @$ns $d A"
dig @$ns $d A | eval $g</pre>

It is a good replacement instead of $() or `` or running just a variable.

=== [http://unixhelp.ed.ac.uk/CGI/man-cgi?find Find] ===

==== [http://www.cyberciti.biz/faq/linux-unix-osx-bsd-find-command-exclude-directories Exclude directories] ====

==== [http://www.cyberciti.biz/tips/linux-findinglocating-files-with-find-command-part-1.html Guide Part 1] ====

[http://content.hccfl.edu/pollock/unix/findcmd.htm Find Help] (this includes [http://www.unix.com/tips-tutorials/20526-mtime-ctime-atime.html mtime] commands)

<pre>find . -maxdepth 1 -type f -printf "%f\n" | sed s/,$//</pre>

'''Finds all files that contain "some string"'''. This command is useful in a directory (e.g. mail), so you would do ls -lah | grep year-mm then:

<pre>find . -type f -exec grep -l "some string" {} \;</pre>

=== [http://www.thegeekstuff.com/2011/07/bash-for-loop-examples for loop examples] ===

=== Functions ===

A prime use of functions is in our script to replace the date.timezone settings in php.ini at http://serverkb.co.uk/tools/phptimezone.sh

<pre>#!/bin/bash
APACHEPHP="/etc/php5/apache2/php.ini"
CURRENT="\n\nThis is the current timezone configuration:"
DONE="If the settings were wrong, they are as below now:"
ETC="/etc/php.ini"

function UBDEB(){
echo -e "\nThe operating system is Debian/Ubuntu, so editing $APACHEPHP" $CURRENT
grep "date." $1 | head -7 | grep -v '; http\|Define' ; echo ""
sed -i -e 's/;date.timezone\ =/date.timezone\ =\ \"Europe\/London\"/g' $1
sed -i -e 's/;date.default_latitude\ =\ 31.7667/date.default_latitude\ =\ 51.500181/g' $1
sed -i -e 's/;date.default_longitude\ =\ 35.2333/date.default_longitude\ =\ 0.12619/g' $1
echo $DONE
grep "date." $1 | head -7 | grep -v '; http\|Define' ; echo ""
}

function RHEL(){
echo -e "\nThe operating system is likely CentOS, editing $ETC" "$CURRENT
grep "date." $1 | head -7 | grep -v '; http\|Define' ; echo ""
sed -i -e 's/;date.timezone\ =/date.timezone\ =\ \"Europe\/London\"/g' $1
sed -i -e 's/;date.default_latitude\ =\ 31.7667/date.default_latitude\ =\ 51.500181/g' $1
sed -i -e 's/;date.default_longitude\ =\ 35.2333/date.default_longitude\ =\ 0.12619/g' $1
echo $DONE
grep "date." $1 | head -7 | grep -v '; http\|Define' ; echo ""
}

if [[ `cat /etc/issue | sed '1 ! d' | awk '{print $1;}'` == "Debian" || `cat /etc/issue | sed '1 ! d' | awk '{print $1;}'` == "Ubuntu" ]];
then
UBDEB "$APACHEPHP"
else
RHEL "$ETC"
fi</pre>

Credit to Sam Teale for helping me with this.

=== Grep ===

If you are grepping a a .gz or .zip file you generally need to use zgrep.

==== Exclude multiple directories ====

<pre>grep 'string' -R . -il --exclude="/proc" --color
grep -iR "string" * | grep -v "/proc"</pre>

==== Look for IP address ====

do this:

grep -E -o '(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)'

courtesy of [http://stackoverflow.com/questions/427979/how-do-you-extract-ip-addresses-from-files-using-a-regex-in-a-linux-shell/428086#428086 SO]

==== Multiple terms ====

Exclude using -v

<pre>grep 'chroot\|default\|fs\|fs-passwd\|httpsdocs'</pre>

'''It is important to remember to not put a \| after the last text term.'''

This can be used with tail as well.

==== Remove pipe symbols from MySQL ====

mysql -pPASSWORD admin -e"select domain from domains;" grep -v "|" > FileWithoutPipes

==== Switches/flags ====

<pre>-A after
-B before</pre>

==== Wildcards for filepaths ====

From http://unix.stackexchange.com/questions/203195/wildcards-for-filepaths-arent-working-in-grep :

<pre>* in a regex is not like a filename glob. It means 0 or more of the previous character/pattern. So your examples would be looking for a A then 0 or more B then -DEF
. in regex means "any character" so you could fix your pattern by using
grep 'AB.*DEF'</pre>

=== Head ===

If for example you do /var/qmail/bin/qmail-qstat and it prints two separate lines, do this to get just the first line:

head -1

=== [http://www.dreamsyssoft.com/unix-shell-scripting/ifelse-tutorial.php If and Else] ===

[http://tldp.org/LDP/Bash-Beginners-Guide/html/sect_07_02.html Advanced if usage]

Use -f for files, -d for directories

<pre>if [ -f $VARIABLE ]
then
parameters (e.g. echo, mkdir, touch, rm)
fi</pre>

Combine if and $? to get to do something with the exit status of the last executed command.

<pre>if [ $? -eq 0 ]; then
commands
fi</pre>

If you want to prompt for both y and Y for yes input, use:

<pre>if [[ $variable1 = y || $variable2 = Y ]];</pre>

Another example of the above if x '''or''' y is [http://www.unix.com/302444803-post5.html here]. Use || to do if = x or y.

<pre>if [[ value = x || y ]</pre>

If you get the following error when executing a bash script outside of it's directory:

[[: not found

You need to either bash /file/path/to/script or alter the syntax to use:

<pre>-eq instead of =</pre>
or
<pre>(( command )) instead of [[ command ]]</pre>

=== If value equals multiple values ===

Using the syntax above:

<pre>echo -ne "Enter a server number (1, 2 or 3): "
read ServerNo

if [[ ( $ServerNo -eq 1 ) || ( $ServerNo -eq 2 ) || ( $ServerNo -eq 3 ) ]]; then
echo "$ServerNo is a valid server, continuing."
else
echo "$ServerNo is not a valid server, exiting."
fi</pre>

=== read ===

One of the simplest uses of this command is to do it like so:

<pre>echo -ne "Enter the filename you want to create: "
read createdfilename
touch $createdfilename</pre>

=== sed ===

If you want to '''get rid of/cut certain/specific lines/rows from STDOUT''' aka '''print a specific line''', use sed in this way:

sed '22 ! d'

This is for use ''without'' a file. This example will only display the 22nd row from your output.

Notes: Blank lines count as a row. The command awk 'NR==22' would do the same.

'''To print individual/separate lines, e.g. 1, 4 and 5:'''

sed -ne '1p;4p;5p'

'''To print between lines 22 to 39:'''

sed '22,39 ! d'

'''To put a variable inside sed, use quotes instead of apostrophes:'''

sed "22,$variable ! d"

'''To delete parenthesis/brackets, use this:'''

sed 's/['''()''']//g' 
sed 's/[''')''']//g' 
sed 's/['''(''']//g' 
sed 's/['''[]''']//g' 
sed 's/[''']''']//g' 
sed 's/['''[''']//g'

==== Replace text in a file ====

sed -i -e 's/TextToFindToReplace/TextToReplaceItWith/g' filename

To handle spaces, forward slashes and quotes " ", use back slashes like you do in filenames:

sed -i -e 's/'''File\"quotes\"WithA\ Space'''/''HereIs''\/''ABackslash''/g' filename

=== sleep and usleep ===

Use sleep if you want to "wait" X seconds. usleep is measured in microseconds and cannot do more than 1 second. 100000 (100,000 / 100k) = 0.1 seconds. 1,000,000 = 1 second.

=== Shells and subshells ===

If you want a script to make changes to your current shell, not the subshell a bash script works in, execute the script by doing the following (sometimes you may need to do ./ still):

<pre>. script</pre>

This information was provided by these sources: [http://stackoverflow.com/questions/874452/change-current-directory-from-a-script 1], [http://stackoverflow.com/questions/255414/why-doesnt-cd-work-in-a-bash-shell-script 2]

=== tee ===

Tee command is used to store and view (both at the same time) the output of any other command.

Tee command writes to the STDOUT, and to a file at a time.

By default the tee command overwrites the file. You can instruct tee command to append (like >> does) to the file using the option –a as shown below.

<pre>ls | tee –a outputfile</pre>

=== [http://mywiki.wooledge.org/BashFAQ/031 Use [[ instead of [] ===

=== Variables ===

If you store a variable with a command within it as follows:

<pre>variablename=`command`</pre>

you should instead store it like this:

<pre>variablename=$(command)</pre>

And then call it as follows:

<pre>${variablename}</pre>

=== Watch ===

Example/s:

To monitor a file's size:

<pre>watch -n 1 'ls -lh | grep filename'</pre>

=== xargs ===

This can be incredibly useful if you get "Argument list too long"

cd /to/directory , find . -type f | xargs rm -Rf

If you need to remove a list of files with spaces in them, do this:

<pre>ls -lah | grep "SpecificString" | awk '{print $9,$10,$11,$etc}' | xargs -I {} rm -v {}</pre>

Use ls -lh to not include hidden files/file starting with a full stop.

For simple removal of normal files do this in a screen session:

<pre>ls -lh | awk '{print $9}' | xargs -t rm</pre>

Otherwise try using find:

<pre>find . -exec grep PATTERN {} + | wc -l</pre>

Copying multiple files:

<pre>ls -lh | grep TEXT | awk '{print $9}' | xargs cp -t /target/path/</pre>

== Compare a remote file with a local file ==

ssh user@host cat /path/to/remotefile | diff /path/to/localfile -

Credit to User [http://www.commandlinefu.com/commands/by/root Root]

=== Compare files in a directory ===

diff -bur folder1/ folder2/

Warning: when doing diff on folders, if the timestamps are different it will think the files are different. If you actually compare the files, they will be the same.

== Console Clock in corner ==

while true; do echo -ne "\e[s\e[0;$((COLUMNS-27))H$(date)\e[u"; sleep 1; done &

'''Warning, this auto scrolls your SSH session'''. To kill it, do:

ps aux | grep bash | grep -v grep

Then kill the bash session at the time you ran it:

kill <processid>

Credit to User [http://www.commandlinefu.com/commands/by/SQUIIDUX Squiidux]

 -->

== Create symlink ==

https://www.cyberciti.biz/faq/creating-soft-link-or-symbolic-link/

How to chown a symlink: https://superuser.com/questions/68685/chown-is-not-changing-symbolic-link

Old method:

<pre>ln -s TARGET LINK_NAME</pre>

== Cronjob/Crontab ==

To check a cronjob has at least attempted to run/execute, check this at the time of execution:

<pre>tail -f /var/log/syslog | grep CRON</pre>

[http://www.openjs.com/scripts/jslibrary/demos/crontab.php Generator]

<pre>crontab -e
crontab -l

* * * * * command to be executed
- - - - -
| | | | |
| | | | +----- day of week (0 - 6) (Sunday = 0 or 7)
| | | +------- month (1 - 12)
| | +--------- day of month (1 - 31)
| +----------- hour (0 - 23)
+------------- min (0 - 59)
</pre>

Guides:

http://www.adminschoice.com/crontab-quick-reference

To do a job every X minutes, do */X * * * *

To do a job every minute in a specific hour, do * X * * *

To do a job every X hours, do * */X * * *

To do a job every day at X hour on the hour, do 0 9 * * * for 9am each day.

To do a job every week at 2am on Sunday, do 0 2 * * 0

To monitor active cron jobs, do tail -f /var/log/cron

=== /usr/local/bin/php: No such file or directory ===

Do whereis php

Generally it is actually in /usr/bin/php

== Cron Daemon email ==

If you get the below email:

<pre>cd / && run-parts --report /etc/cron.daily
/etc/cron.daily/sysklogd:
chown: cannot access `/var/log/mail.warn': No such file or directory
chown: cannot access `/var/log/syslog': No such file or directory
chown: cannot access `/var/log/mail.info': No such file or directory</pre>

Do the following:

<pre>cd /var/log
touch /var/log/mail.warn /var/log/syslog /var/log/mail.info
/etc/init.d/sysklogd restart</pre>

== Date ==

=== Spaces ===

To put spaces between variables (e.g +%H%M) use single quotes:

<pre>The time is `date '+%R:%S %Y %Z'` on the following Day/Month/Year `date '+%a %b %d'`</pre>

== Echo colours ==

[http://misc.flogisoft.com/bash/tip_colors_and_formatting Tips for colours and formatting]

Place 0; for the normal version (e.g. Black is 0;30) 
Place 1; before these to get the light colour version.

Here are the colour codes:

{| border="1" align="center" style="text-align:center;" class="collapsible collapsed wikitable"
|-
! colspan="3"|
|-
|'''Colour'''
|'''Foreground'''
|'''Background'''
|-
|Black
|30
|40
|-
|Dark Grey
|1;30
|1;40
|-
|Red
|31
|41
|-
|Light Red
|1;31
|1;41
|-
|Green
|32
|42
|-
|Light Green
|1;32
|1;42
|-
|Yellow
|1;33
|1;43
|-
|Brown
|0;33
|0;43
|-
|Blue
|34
|44
|-
|Light Blue
|1;34
|1;44
|-
|Magenta (Purple)
|35
|45
|-
|Light Purple
|1;35
|1;45
|-
|Cyan
|36
|46
|-
|Light Cyan
|1;36
|1;46
|-
|White
|37
|47
|-
|Light Gray
|0;37
|0;47
|-
|}

An example:

<pre>#!/bin/bash

wipe="\033[1m\033[0m"

black="40m"
darkggrey='\E[1;30m'
red='\E[31m'
lightred='\E[1;31m'
green='\E[32m'
lightgreen='\E[1;32m'
yellow='\E[1;33m'
brown='\E[0;33m'
blue='\E[34m'
lightblue='\E[1;34m'
purple='\E[35m'
lightpurple='\E[1;35m'
cyan='\E[36m'
lightcyan='\E[1;36m'
white='\E[37m'
lightgray='\E[0;37m'
green='\E[32m;'</pre>

<pre>echo -e "$green$black"
echo Hello World
echo -e "$wipe"</pre>

or

<pre>echo -e "Output a ${green}coloured${wipe} word."</pre>

<pre>./colourtest.sh

Hello World</pre>

The Hello World text appears green.

== Execute one off command whenever ==

echo "ls -l" | at midnight

This is an alternative to cron which allows a one-off task to be scheduled for a certain time.

Credit to User [http://www.commandlinefu.com/commands/by/root Root]

== File Locations (index priority) ==

/etc/apache2/mods-enabled/dir.conf (on Ubuntu) or /etc/httpd/conf/httpd.conf (on CentOS, ~line 402) and it should show something like:

<pre>DirectoryIndex index.html index.html.var index.shtml index.cfm index.php index.htm</pre>

This shows the default priority in which the index page is picked up and this can be set in the [[.htaccess]] file as well with:

<pre>DirectoryIndex index.html index.php</pre>

These are good places to check if you are using all of your [[Resource_Usage|disk space]].

cd /var/log 
cd /var/www/vhosts (website and statistics) 
cd /var/lib/mysql (database) or mysql/mysql 
cd /usr/bin/mysqldump (mysql dump) 
cd var/qmail (mail logs, queue and configuration) 
cd /var/lib/psa/dumps (physical Plesk backups) 
cd opt/psa/tmp/ (Plesk stores temporary files here for backups)

== File Permissions ==

[http://linuxcommand.org/lts0070.php One of the best permissions guide]

The values and their equivalent permissions. R is Read, W is Write and X is Execute. There are three sets on a file or folder (e.g. -rwx-w--w- , -rw-r--r-- , -rwxr-xrwx) so you need to put in a value of three (or four in rare occasions) for a file/folder e.g. 644.

<pre>0 --- 
1 --x
2 -w-
3 -wx
4 r--
5 r-x
6 rw-
7 rwx</pre>

'''The syntax for chmod is (for example) 755 fileorfolder. The -R option can also be used to set the permissions on anything below a folder.''' 
'''The syntax for chown is chown user:group fileorfolder . To apply the user:group to anything below a folder you need to use the -R option.'''

[http://permissions-calculator.org/ Permissions Calculator] 
[http://www.tuxfiles.org/linuxhelp/filepermissions.html Help Guide 1] 
[http://www.freeos.com/articles/3127?page=3 Help Guide 2] 
[http://en.wikipedia.org/wiki/Filesystem_permissions#Notation_of_traditional_Unix_permissions Unix Notation] 
[http://www.faqs.org/docs/linux_intro/sect_03_04.html File protection with chmod]

If you use PHP Support as '''Apache module, it will use the third value of''' -rw- r-- '''r-x''' to permissions. If it is using '''Fast CGI it will use the user:group''' for the first two values '''-rwx rw-''' --x

If you are using Plesk a good place to check if you are getting Forbidden errors on your website is /var/www/vhosts/yourdomain.com/httpdocs/statistics/logs/error_log . Access your site and tail -f that file. If you get .htaccess pcfg_openfile: unable to check htaccess file, ensure it is readable name your .htaccess file correctly, set your httpdocs to 757 and see [http://serverfault.com/questions/61726/permission-denied-home-htaccess-pcfg-openfile-unable-to-check-htaccess-file this link].

'''Special permissions'''

There is also a, g & s which are not widely used as it just needs additional representation at the special/setid permission to the group.

To set a file to -rws--x--x for example use

<pre>4 = setuid - s
2 = setgid - s
4 + 2 = S
1 = Sticky Bit
4 + 2 + 1 = T
2511 -r-x--s--x (e.g. /var/qmail/bin/qmail-remote or /var/qmail/bin/qmail-queue)
4655 -rwSr-xr-x
4711 -rws--x--x
4744 -rwsr--r--
4755 -rwsr-xr-x
6411 -r-S--s--x.
6511 -r-s--s--x
6644 -rwSr-Sr--
6666 -rwSrwSrw-
7000 ---S--S--T
7644 -rwSr-Sr-T
7711 -rws--s--t
7744 -rwsr-Sr-T
7755 -rwsr-sr-t</pre>

[http://serverfault.com/questions/111350/what-chmod-and-ownergroup-settings-are-best-for-a-web-application Owner and Group advice for websites]

== [http://adminlogs.info/2011/06/02/linux-find-command-tips Find command guide] ==

== [http://serverfault.com/questions/35076/need-to-fix-file-permissions-in-a-users-home-directory Fix file and folder permissions easily] ==

== FreeBSD ==

* mysqldump location: /mysql/bin/mysqldump
* Remove syntax:

- rm -r folderName
* Generic tunneling interface starts with gif

=== [http://forums.freebsd.org/showthread.php?t=5852 Check software versions] ===

=== fetch instead of wget ===

To download a file.

=== whereis instead of locate command ===

To find files/folders.

== Full Directory listing ==

<pre>apt-get install tree
yum install tree
tree > tree.txt</pre>

If you feel adventurous do cat tree.txt , it will take a while ;)

=== Find the deepest directory in your server/file structure ===

<pre>find . -type d -printf '%d:%p\n' | sort -n | tail -1</pre>

=== Find and remove specific file types from current directory ===

<pre>cd into the directory
find . -type f -name '*.filetype' -exec rm -v {} \;</pre>

=== Line count a file ===

wc -l /file/path

== Generate random number ==

Between 1 and 10:

seq 10| shuf | head -1

== GeoIP - Block countries accessing website ==

Ubuntu: apt-cache search geoip ; apt-get install geoip-database libgeoip-dev libgeoip1 python-geoip geoip-bin libapache2-mod-geoip tclgeoip 
CentOS: yum list |grep -i geo , yum install GeoIP.x86_64 
http://www.webhostingtalk.com/showthread.php?t=959646 
http://askmatt.co.uk/blog/2010/05/block-countries-using-apache-mod-geo-ip-list-of-countries-by-fraud-risk

== Gunzip and Zip ==

To gzip a file (.gz) up, do:

<pre>gzip file</pre>

The above won't work for folders.

Or if zip is installed:

<pre>zip -r filename.zip filename</pre>

To unzip a .gz file, do:

<pre>gunzip file</pre>

To extract a .tgz file, do:

<pre>tar zxvf fileNameHere.tgz</pre>

See http://serverkb.co.uk/wiki/Linux#tar_command for further details.

=== 7zip ===

Byron Galietta <byrontcg@gmail.com>
Tue, 4 Apr 2017, 18:39
to me

https://www.howtoforge.com/tutorial/how-to-install-and-use-7zip-file-archiver-on-ubuntu-linux/

DO NOT USE the 7-zip format for backup purpose on Linux/Unix because :
- 7-zip does not store the owner/group of the file.

On Linux/Unix, in order to backup directories you must use tar :
- to backup a directory : tar cf - directory | 7za a -si directory.tar.7z
- to restore your backup : 7za x -so directory.tar.7z | tar xf -

If you want to send files and directories (not the owner of file) to others Unix/MacOS/Windows users, you can use the 7-zip format.
example : 7za a directory.7z directory

Do not use "-r" because this flag does not do what you think.

Do not use directory/* because of ".*" files (example : "directory/*" does not match "directory/.profile")

https://www.unixtutorial.org/2014/08/7zip-ubuntu/

== [http://eng.eelcowesemann.nl/plesk/changing-the-servers-hostname-in-plesk Hostname guide] (rough) ==

If the server runs Plesk and Virtuozzo, the permanent one needs setting on the hardware or in Virtuozzo.

Run dig -x IP.IP.IP.IP from any Linux server and it will show you the PTR/hostname.

'''Note:''' Most servers by default come with a non resolving hostname of localhost, localhost.localdomain or something generic.

The hostname should never be left as the default value on a server sending mail, as it is one of three things mail recipient's mailservers see to determine if mail is spam or not. The other two are reverse DNS and the SMTP banner.

If Plesk throws an error when clicking Websites & Domains tab regarding hostname -f, see [[Plesk_Errors#Domains_area_is_blank | this resolution]].

== How to fix broken packages ==

Run the following commands below:

<pre>dpkg --configure -a
apt-get install -f
#or
apt-get -f install</pre>

If the problem still exists, then edit dpkg status file:

<pre>gksudo gedit /var/lib/dpkg/status</pre>

Find the package in question, and remove everything that has anything to do with it and save the file.

== How to install .deb files ==

<pre>dpkg -i filename.deb</pre>

== [[.htaccess]] ==

[http://en.wikipedia.org/wiki/Htaccess HyperText access]

== [http://stackoverflow.com/questions/653096/howto-free-inode-usage inode usage] ==

<pre>df --si
df -ih</pre>

A lot of the time the cause can be /tmp (/var/lib/php/session/ on Plesk) due to sessions. You may want to delete the files in there.

== Investigating high load ==

If you are getting a high load average in top, these are some of the steps you can take to investigate the issue.

Check which process has the most open of itself:

<pre>ps aux | awk '{print $11}' | sort | uniq -c | sort -nk1 | tail -n5</pre>

Stop that process, then run the above command a second time. Then start it again and run the command a third time.

=== Useful software ===

* top
* htop
* iotop

All these will do the job. Firstly check the CPU wait time, this is shown within top in Cpu(s): 8.0%us, 2.8%sy, 0.0%ni, 40.7%id, 48.3%wa

<pre>%wa in</pre>

If this is high, check the Status column (S column in top) to see if any are labelled D. The [http://stackoverflow.com/questions/666783/how-to-find-out-which-process-is-consuming-wait-cpu-i-e-i-o-blocked processes blocked on IO] are the ones marked as D.

=== On a Plesk server ===

Ensure sites are running PHP as Fast CGI Application instead of Apache module so you can see which USER the process is running as. Pressing the letter "c" on your keyboard will show the path and normally the website name.

<pre>wget http://serverkb.co.uk/tools/memcpu.sh ; chmod +x memcpu.sh ; ./memcpu.sh > usage.log &
tail -f usage.log</pre>

You can alter the PHP Handler on Plesk boxes in the psa database easily by doing:

<pre>mysql -uadmin -p`cat /etc/psa/.psa.shadow`;
use psa
select * from hosting\G
select dom_id,www_root,php_handler_type from hosting;
update hosting set php_handler_type="module" where dom_id=x;</pre>

If sites run PHP as an Apache module scripts will execute as the Apache user www-data, this can make it difficult to see which site they belong to. This also means scripts run with privileges of the Apache user so if an account is compromised an attacker can get access to all other accounts. Also running as Apache module can make the Apache process CPU report look artificially high. Running PHP as Fast-CGI executes scripts as an FTP user associated with each subscription allowing easier identification of problem scripts and limit the damage of rogue scripts.

CPU reports are not an easy way to determine server health. We'd recommend you look at changes and trends rather than the absolute numbers. Most importantly consider your real world performance.

== Linux Container ==

This install below is for an Ubuntu physical server, I may update this in the future for CentOS, Fedora and others.

https://help.ubuntu.com/12.04/serverguide/lxc.html

If you need to get file off the container, you can just scp it off. If the recipient server is slow, try moving the file to the host machine by doing:

scp -Psshport file root@hostIPaddress:~

=== Installation of LXC ===

<pre>apt-get install lxc
cat /etc/init/lxc-net.conf | grep USE_LXC_BRIDGE</pre>

If true set to false unless you want the containers to NAT to your servers real IP addresses, and to be accessible externally.

=== Pre-container creation steps ===

To reduce errors pre-container creation do the following:

<pre>dpkg-reconfigure locales
locale-gen en_GB
update-locale LANG=en_GB.UTF-8</pre>


=== Creating/deleting containers ===

[http://wiki.openvz.org/Download/template/precreated OpenVZ Template list]

Check the templates below and pick one:

<pre>cd /usr/lib/lxc/templates/ ; ls -lah</pre>

Create a container from one of the templates:

<pre>lxc-create -t ubuntu -n NameOfTheContainer</pre>

If you want to install the fedora package, do apt-get install yum

To delete it just do:

<pre>lxc-destroy -n NameOfTheContainer</pre>

=== Start/stop a container ===

<pre>lxc-start -n NameOfTheContainer -d</pre>

/etc/init.d/lxc stop

=== Access the container ===

The default user is 'ubuntu' with the password 'ubuntu', to enter a container, do:

<pre>lxc-console -n NameOfTheContainer
sudo -i</pre>

Exit using Ctrl + a, then press q

To re-enter the container, do lxc-console -n NameOfTheContainer and then press enter (you may have to a few times)

'''Access externally:'''

iptables -t nat -A PREROUTING -p tcp --dport 2222 -j DNAT --to 10.0.3.61:22

'''Make sure you remove this rule afterwards and DO NOT reboot your server.'''

=== Configuration settings ===

* By default you can ping a container from the host, and vice versa, and you can ping the outside world from the container.
* You can set the hostname just like a normal server, if you want to rename the container.

==== Default configuration of system files ====

<pre>cd /var/lib/lxc/nameofcontainer/rootfs/etc/sysconfig/network-scripts
vim ifcfg-eth0</pre>
<pre>DEVICE=eth0
BOOTPROTO=dhcp
ONBOOT=yes
HOSTNAME=phptester
NM_CONTROLLED=no
TYPE=Ethernet
MTU=</pre>

<pre>vim /var/lib/lxc/nameofcontainer/config</pre>
<pre>lxc.network.type=veth
lxc.network.link=lxcbr0
lxc.network.flags=up
lxc.network.hwaddr = MAC Address
lxc.utsname = MT</pre>

<pre>vim /etc/lxc/lxc.conf</pre>
<pre>lxc.network.type=veth
lxc.network.link=lxcbr0
lxc.network.flags=up</pre>

You can add the below to /etc/network/interfaces

<pre>auto br1
iface br1 inet dhcp
bridge_ports eth0</pre>

==== Fedora ====

The mirrors/repositories the container uses may be broken by default, don't try to install anything. You'll likely get:

''Error: Cannot retrieve repository metadata (repomd.xml) for repository: fedora. Please verify its path and try again''

And you likely won't be able to ping anything except the host machine and localhost/127.0.0.1

iptables -t nat -A POSTROUTING -s ContainerIP/24 -j SNAT --to-source PhysicalHostIP 
iptables -t nat -A PREROUTING -m tcp -p tcp --dport 10022 -j DNAT -i eth0 --to-destination ContainerIP:80 
iptables -t nat -A PREROUTING -m tcp -p tcp --dport 10443 -j DNAT -i eth0 --to-destination ContainerIP:443

[https://www.berrange.com/posts/2011/09/27/getting-started-with-lxc-using-libvirt libvirt]

<pre>vi /etc/yum.repos.d/fedora.repo
vi /etc/yum.repos.d/fedora-updates.repo</pre>

Uncomment (#) the lines starting with "baseurl"

yum update

==== OpenSUSE ====

[http://en.wikipedia.org/wiki/OpenSUSE#Version_history Version history]

http://www.lacerta.be/d7/content/opensuse-lxc-container-inside-ubuntu

=== List containers ===

lxc-list

=== Set passwords ===

Log in as the root user of the container:

'''Fedora''' container:

<pre>Username: root
Password: root</pre>

Set the root password to something different:

<pre>passwd</pre>

You will need to do yum install vim when inside the server.

'''Ubuntu''' container:

<pre>sudo -i
Username: ubuntu
Password: ubuntu</pre>

Set the user's password:

<pre>passwd ubuntu</pre>

Set the root user's password:

passwd

=== SSH in externally ===

'''To route from externally through the host to the container, just do the below iptables rule''':

<pre>iptables -t nat -A PREROUTING -p tcp --dport 1337 -j DNAT --to 10.0.4.60:22
iptables-save</pre>

In the above case we are saying:

- You want to SSH in on port 1337 
- The container's eth0 IP address is 10.0.4.60 
- Then below we are saying the physical machine has an IP address of 110.111.112.113

Then externally from the server do:

<pre>ssh root@110.111.112.113 -p2222</pre>

And bingo! You should be in the container.

<pre>passwd</pre>


== [http://wiki.debian.org/LSBInitScripts LSB Init Scripts] ==

== ls list only directories or files ==

Directories:

<pre>ls -lad */</pre>

Files:

<pre>ls -la | grep -v ^d</pre>

== Kill tty session ==

<pre>w
ps aux | grep bash | grep -v grep
ps aux | grep tty | grep -v grep
kill -HUP <processid></pre>

[http://www.cyberciti.biz/faq/howto-kill-unix-linux-user-session Further info]

== Maldet ==

[http://www.rfxn.com/projects/linux-malware-detect Documentation] 
[http://www.rfxn.com/downloads/maldetect-current.tar.gz Maldet .tar.gz] 
[http://blog.hostonnet.com/how-to-install-and-configure-maldet-linux-malware-detect-lmd Install and Configure]

<pre>cd /root ; wget http://serverkb.co.uk/tools/maldet.sh ; chmod +x maldet.sh ; ./maldet.sh</pre>

Always run your scans from chroot environment (if it has one/is possible) and in Screen (screen -S NameIt), and detach by doing CTRL + A, then press D

Scan reports are normally stored in /usr/local/maldetect/sess/ as session. files.

maldet -a -e -l filepath

== Manually alter time/date ==

'''Ubuntu'''

<pre>date
date mmddtimeyear #as seen below</pre>

'''Cent OS'''

<pre>cd /etc/
ls -lah
rm localtime
ln -s /usr/share/zoneinfo/Europe/London /etc/localtime
date mmddtimeyear
| | | | ---> 2012
| | | 24hr --> XX:XX without :
| | dd -------> day
| mm ---------> month

/etc/init.d/ntpd restart or start
date</pre>

== Move files into your home directory not owned by your own user ==

Copy to /var/tmp or /tmp (for small files) and do:

<pre>chmod ugo+rw <filename></pre>

== PID ==

Under construction.

Process ID.

To determine the usage of a specific process, do top -p PID

The maximum number of pids can be obtained from /proc/sys/kernel/pid_max

== .profile ==

Put this in .profile file for on user startup:

<pre>echo "" ; df -h | sed -ne '1p;5p' ; echo "rootfs"
echo "" ; free -m
echo "" ; w | head -1 | sed 's/^ *//g'
echo "" ; w | tail -10 | grep -v average ; echo ""</pre>

== Proxmox ==

To access via the web go to https://IPaddress:8006

Rough notes:

apt-get install sudo

Proxmox

/var/lib/vz

dump is for backups 
images is for OS images 
private is for OpenVZ container file systems 
template/cache is for OpenVZ templates

http://openvz.org/Download/template/precreated

Create VM creates KVM 
Create CT creates OpenVZ container 

vzctl enter id 
vzctl start/stop id 

iptables -t nat -A POSTROUTING -o vmbr1 -j MASQUERADE 
restart networking on host and CT

=== cman_tool: Cannot open connection to cman ===

<pre>pvecm status
pvecm nodes
cman_tool: Cannot open connection to cman, is it running ?</pre>

<pre>service pve-cluster restart
pvecm delnode NodeName</pre>

=== Force remove an OpenVZ container ===

<pre>vzctl stop 100 ; vzctl destroy ContainerID
cd /var/lib/vz/private
rm ContainerIDfolder -R
cd /var/lib/vz/root
rm ContainerIDfolder -R
cd /etc/pve/nodes/ContainerName/openvz
mv ContainerID.conf ContainerID.bak</pre>

Make sure it does not exist in cat /etc/pve/.members

=== Remount a logical partition/volume ===

lvdisplay

/dev/mapper/pve-data /var/lib/vz (this will be different in your file system)

=== Unable to get local IP address ===

<pre>/etc/init.d/pve-cluster restart
service pve-cluster start
Starting pve cluster filesystem : pve-cluster[main] crit: Unable to get local IP address
(warning).</pre>

Make sure in /etc/hosts your domain name resolves to the server and you also have it without the .co.uk/.com etc in the file as so:

<pre>ServerIPaddress domain.co.uk domain pvelocalhost
127.0.0.1 localhost localhost.localdomain</pre>

Then do:

<pre>/etc/init.d/hostname.sh stop
/etc/init.d/hostname.sh start
service pve-cluster start</pre>

=== Transport endpoint is not connected ===

<pre>df -h
df: `/etc/pve': Transport endpoint is not connected</pre>

<pre>ls -lah /etc/pve
ls: cannot access pve: Transport endpoint is not connected
d????????? ? ? ? ? ? pve</pre>

Do this:

<pre>umount /etc/pve
pvecm status</pre>

You will get:

unable to get IP for node 'hostname' - node offline?

The fix is the same as [[Linux#Unable_to_get_local_IP_address | this]] one, ensure you have the domain without the web extension in /etc/hosts resolving to the servers IP address. Then do:

service pve-cluster start

== Recover deleted files ==

You need to install this software before you delete any files:

<pre>apt-get install foremost</pre>

Then see this documentation:

https://help.ubuntu.com/community/DataRecovery 
http://ddailygirl.wordpress.com/2010/08/17/recovering-files-after-rm-in-linux 
http://www.howtoforge.com/recover-deleted-files-with-foremost 
http://www.webupd8.org/2009/03/recover-deleted-files-in-ubuntu-debian.html

== Remove file starting with dash ==

<pre>rm -- -filename</pre>

Remove folder starting with dash

<pre>rm -rf -- -folder/</pre>

== Remove/rename file called tilde ==

<pre>mv '~' newfilename
rm '~'</pre>

== Restart service or service ==

Useful for differently named ones, e.g.

[ -f /etc/init.d/mysqld ] && service mysqld restart ; [ -f /etc/init.d/mysql ] && service mysql restart

[ -f /etc/init.d/httpd ] && service httpd restart ; [ -f /etc/init.d/apache2 ] && service apache2 restart

== Roughly list file count ==

This includes nested directories:

<pre>find /full/file/path -type f | wc -l</pre>

== SCP Command - Secure Copy ==

To secure copy a file from one Linux server to another, use the following syntax form:

<pre>scp -P PORT file user@IPAddress:/filepath</pre>

For example:

<pre>scp -P 22 index.html root@127.0.0.1:/</pre>

To move a folder, put -r in between the port and the file(s)/folder(s) like so:

<pre>scp -P 22 -r testdirectory/ root@127.0.0.1:/</pre>

If you receive the following error while trying to SCP a file from one server to the other:

<pre>stdin: is not a tty</pre>

You can solve the issue quickly by doing the following on the destination server:

<pre>vi ~/.bashrc

if [ $(expr index "$-" i) -eq 0 ]; then
return
fi</pre>

== Screen ==

Re-join screen session

<pre>screen -r</pre>

or

<pre>screen -D -r '1234.somescreensession'</pre>

A better alternate is [[Linux#tmux | tmux]].

[http://www.ubuntugeek.com/screen-manages-multiple-sessions-on-one-terminal.html#more-1415 Manage Multiple sessions in one Terminal] 
[http://www.samsarin.com/blog/2007/03/11/gnu-screen-working-with-the-scrollback-buffer Scrollback] (vim /home/.screenrc + defscrollback 1000) 
[http://polishlinux.org/howtos/screen-tips-tricks Tips and Tricks]

== Setting the time ==

http://geoffhankerson.com/node/112 
http://codeghar.wordpress.com/2007/12/06/manage-time-in-ubuntu-through-command-line/

== Standard redirection ==

http://www.xaprb.com/blog/2006/06/06/what-does-devnull-21-mean/

STDIN, STDOUT and STDERR.

0, 1 and 2

1>/dev/null 
2>/dev/null

== sudo ==

If you exit out of root access and want to run the last command you entered without authentication, do:

<pre>sudo !!</pre>

== System Logs and Shutdown troubleshooting ==

If you are having an issue, a reboot should not be performed if the server can be accessed in any way (e.g. locally in the data centre, only if it is a Dedicated server). This is because after a reboot there is little you can find out from the logs as the important logs get cleared on restart.

<pre>last reboot
last</pre>

Do this to check which files exist:

ls -lh /var/log/syslog ; ls -lh /var/log/kern.log ; ls -lh /var/log/dmesg ; ls -lh /var/log/messages

Then do one or more of these depending on which exist:

grep -i error /var/log/syslog ; grep -i panic /var/log/syslog ; grep -i warning /var/log/syslog 
grep -i error /var/log/dmesg ; grep -i panic /var/log/dmesg ; grep -i warning /var/log/dmesg 
grep -i error /var/log/kern.log ; grep -i panic /var/log/kern.log ; grep -i warning /var/log/kern.log 
grep -i error /var/log/messages ; grep -i panic /var/log/messages ; grep -i warning /var/log/messages

errpt may show an error report on some Unix OS'.

To find .log files, run [[Linux#updatedb_.28locate_command.29 | updatedb]] and then locate *.log

To restart and [http://go2linux.garron.me/reboot-check-disks-for-errors-avoid-force-fsck on boot do a disk check] do (or -rF):

<pre>shutdown -Fr now</pre>

== [http://www.pendrivelinux.com/how-to-open-a-tar-file-in-unix-or-linux tar command] ==

To archive and compress a folder/files do:

<pre>tar -czvf files.tgz files/
tar -czvf folder.tar.gz folder/
tar cvf mubackup.tar mu/ ; gzip -9 mubackup.tar

#.tgz is same as .tar.gz</pre>

c creates the archive (tar), z compresses it into the gzip, v is verbose, f is the file/folder

To extract do:

<pre>#for tar
tar xvf file.tar

#for .tgz or tar.gz
tar zxvf file.tar.gz</pre>

[http://www.fluidthoughts.com/howto/tar-gzip/ Guide 1] 
[http://www.thegeekstuff.com/2010/04/unix-tar-command-examples/ Guide 2] 
[http://superuser.com/questions/305128/how-to-specify-level-of-compression-when-using-tar-zcvf 3] and [http://superuser.com/questions/156207/untar-ungz-gz-tar-how-do-you-remember-all-the-useful-options 4]

For bz2 files, use:

<pre>tar -xvjpf file</pre>

== top ==

The TIME column in top is displayed in minutes:seconds.hundredths

== tmux ==

C-c is CTRL+C 
C-m is ENTER

=== New session ===

Latest:

<pre>tmux new -s session_name</pre>

Also possible:

<pre>tmux new-session -s session_name</pre>

Old:

<pre>tmux new-session -n NameTheSession</pre>

=== Detach from a session ===

<pre>CTRL +B then D</pre>

=== Kill session ===

<pre>tmux kill-session -t myname</pre>

If this fails and it says:

"''session not found''"

Do the following:

<pre>tmux ls
tmux kill-session -t X</pre>

- where X is the number of the session on the left.

=== List sessions available ===

<pre>tmux ls</pre>

=== Re-attach to session ===

<pre>tmux attach
tmux attach -t ID or NameTheSession</pre>

=== Remotely execute a command ===

<pre>tmux send-keys -t ID "command" ENTER</pre>

== User ID 99 ==

This is most commonly the user nobody. This can be caused by PHP or done on purpose. cat /etc/passwd | grep 99 ; vim /etc/passwd

== User is not in the sudoers file ==

If you try to sudo into a server or run sudo and get the following message:

"''is not in the sudoers file. This incident will be reported.''"

Do the following command as root and add the username into the file in the same format as the root user:

visudo

== Use unusual characters in filenames ==

If you want to specify a space, lets say the file = /usr/local/etc/'''testingdatabase.sql'''

You need to name the file/folder as follows:

<pre>mv /usr/local/etc/testingdatabase.sql /usr/local/etc/testing\ database.sql</pre>

This will make the file be '''testing database.sql''' , on command line this will appear as '''testing\ database.sql''' .

A backslash symbol \ needs to be used before an apostrophe ' , bracket (), exclamation/bang ! symbol or question marks ?:

<pre>01\ -\ It\'s\ You.txt
#How it appears: 01 - It's You.txt

02\ -\ Boom\!.m3u
#How it appears: 02 - Boom!.m3u

03\ -\ Why\ Wont\ You\ Work\?.sh
#How it appears: 03 - Why Wont You Work?.sh

04\ -\ Musical\ Playlist\ For\ $VPS$\ Server.m3u
#How it appears: 04 - Musical Playlist For (VPS) Server.m3u</pre>

== updatedb (locate command) ==

This command is used when you cannot '''locate''' a file and you get "''locate: warning: database /var/lib/slocate/slocate.db' is more than 8 days old''". It is advised to run updatedb '''at least once a month'''. However if you get the following error when using it:

<pre>updatedb: fatal error: load_file: Could not open file: /etc/updatedb.conf: No such file or directory</pre>

You need to create or edit this file

<pre>vim /etc/updatedb.conf</pre>

and put the following inside of it:

PRUNE_BIND_MOUNTS="yes"PRUNEPATHS="/tmp /var/spool /media"PRUNEFS="NFS nfs nfs4 rpc_pipefs afs binfmt_misc proc smbfs autofs iso9660 ncpfs coda devpts ftpfs devfs mfs shfs sysfs cifs lustre_lite tmpfs usbfs udf"

Alternatively run the below script after reading this file http://serverkb.co.uk/tools/README.txt:

http://serverkb.co.uk/tools/updatedbscript.sh

To vim a file you locate, see [http://stackoverflow.com/questions/8228831/why-does-locate-filename-xargs-vim-cause-strange-terminal-behaviour this]. vim $(command)

=== Cannot find an existing file ===

Ensure that the directory path of the file that '''does''' exist is not in the following section in /etc/updatedb.conf:

<pre>PRUNEPATHS="/tmp /var/spool /media"</pre>


== vim ==

To make a copy the line below where you cursor is, hold CTRL + e. Then put a hash (comment) in front of this line. This is useful for backing up an old value before changing it.

=== Create backup of file whilst in vim ===

<pre>vim file
:!cp % %-</pre>

Press enter and continue to edit

Credit to User [http://www.commandlinefu.com/commands/by/mpb MPB]

=== Enter Insert mode ===

Press the letter i (I)

=== Enter Replace mode ===

Press the letter r (R)

=== E21: Cannot make changes, 'Modifiable' is off ===

<pre>:set modifiable</pre>

=== Search in file for multiple terms ===

Go to search mode i.e. type '/' and then type \v followed by the words you want to search separated by '|' (pipe).

Example:

<pre>/\vword1|word2|word3</pre>

Go to search mode and type the words you want to search separated by '\|'.

Example:

<pre>/word1\|word2\|word3</pre>

The first way puts you in the regular expression mode so that you do not need to put any extra back slashes before every pipe or other delimiters used for searching.

=== See changes made before exiting ===

<pre>:w !diff % -</pre>

=== Editing a jar/zip file ===

(zip#Write) sorry, your system doesn't appear to have the zip pgm

1) Check zip is installed

2)

<pre>:set modifiable
:set write</pre>

3)

E382: Cannot write, 'buftype' option is set

Check if the file has -e on it using:

<pre>lsattr filename</pre>

If so, you likely cannot edit it.

4)

Alternatively, download the file (e.g. a jar) and use an Archive tool like 7-zip to edit it.

== [http://www.cymru1.net/linux-vps/vps-hints-and-tips.php VPS Hints and Tips] ==

To check for the filepath of a command run top and then press c.

If it is a container on a node, there are generally no datacentre / rack level restrictions as the container is virtualised on a node. The only restrictions are what is put in place via the container itself effectively.

To list all open Internet, x.25 (HP-UX), and UNIX domain files, use:

lsof -i -U

== WHOIS script ==

[http://www.ivarch.com/programs/pv.shtml Pipe Viewer], [http://linux.die.net/man/1/pv PV info page]

<pre>apt-get install pv ; cd /var/www/vhosts ; ls -l | awk ' {print $9}' > domainlist ; wget serverkb.co.uk/tools/findregistrar.sh ; chmod +x findregistrar.sh</pre>

For CentOS use yum -y install jwhois.x86_64

Edit the file and replace domain registrar with the one you want to find. Then do:

<pre>./findregistrar.sh</pre>

== write error ==

If you get the following error when doing write user TTYsession or write user Session:

write: write: you have write permission turned off.

Do this to fix the problem:

mesg y

== [http://linuxcommand.org/writing_shell_scripts.php Writing Shell Scripts] ==

Linux

2018-09-18T13:56:37Z

Rootadminacc: /* tmux */

To check your server info, do lscpu 
To run a bash script without executing it, do bash -n scriptname.sh 
To see help commands do command --help or man command. To paste into PuTTY, use SHIFT + INSERT. 
For detailed software and hardware info do apt-get install hardinfo then hardinfo. For CentOS 6 use [http://pkgs.repoforge.org/hardinfo/hardinfo-0.5.1-1.el6.rf.x86_64.rpm this]. 
To write to a user in the same SSH server, do w, get their tty session and then do write user ttySession. If they are root, do write root Session 
[http://www.linuxfocus.org/English/September1999/article103.html Awk introduction], [http://tldp.org/LDP/Bash-Beginners-Guide/html/sect_07_01.html If manual].

== Append date to same line ==

Either of these will work:

<pre>| awk '{ print strftime("%Y-%m-%d %H:%M:%S"), $0; }'
| ts '%F %T'</pre>

To customise date, put a + symbol in front of the flag:

<pre>date +%R
14:32</pre>

To get this format of the date/time:

24 May 2013 10:25:33

Use:

<pre>date +%d\ %B\ %Y\ %H:%M:%S</pre>

== authorized_keys (RSA) ==

This will show you how to SCP, SSH and rSync without prompting for password between two servers.

Whenever you need to use SCP to copy files, it asks for passwords. Same with rSync as it (by default) uses SSH as well. Usually SCP and rSync commands are used to transfer or backup files between known hosts or by the same user on both the hosts. It can get really annoying the password is asked every time. I even had the idea of writing an expect script to provide the password. Of course, I didn't. Instead I browsed for a solution and found it after quite some time. There are already a couple of links out there which talk about it. I am adding to it...

Lets say you want to copy between two hosts host_src and host_dest. host_src is the host where you would run the SCP, SSH or rSync command, irrespective of the direction of the file copy!

On host_src, run this command as the user that runs SCP/SSH/rSync

<pre>ssh-keygen -t rsa</pre>

This will prompt for a passphrase. Just press the enter key. It'll then generate an identification (private key) and a public key. Do not ever share the private key with anyone! ssh-keygen shows where it saved the public key. This is by default ~/.ssh/id_rsa.pub:

Your public key has been saved in <your_home_dir>/.ssh/id_rsa.pub

Transfer the id_rsa.pub file to host_dest by either FTP, SCP, rSync or any other method.

On host_dest, '''login as the remote user which you plan to use when you run SCP, SSH or rSync on host_src'''.

Make sure the folder ~/.ssh exists first, if not do:

<pre>mkdir ~/.ssh</pre>

Copy the contents of id_rsa.pub to ~/.ssh/authorized_keys

<pre>cat id_rsa.pub >>~/.ssh/authorized_keys
chmod 700 ~/.ssh/authorized_keys</pre>

If this file does not exists, then the above command will create it. Make sure you remove permission for others to read this file. If its a public key, why prevent others from reading this file? Probably, the owner of the key has distributed it to a few trusted users and has not placed any additional security measures to check if its really a trusted user.

Note that SSH by default does not allow root to log in. This has to be explicitly enabled on host_dest. This can be done by editing /etc/ssh/sshd_config and changing the option of PermitRootLogin from no to yes. Don't forget to restart SSHD so that it reads the modified config file. Do this only if you want to use the root login.

Well, thats it. Now you can run SCP, SSH and rSync on host_src connecting to host_dest and it won't prompt for the password. Note that this will still prompt for the password if you are running the commands on host_dest connecting to host_src. You can reverse the steps above (generate the public key on host_dest and copy it to host_src) and you have a two way setup ready!

== .bashrc ==

<pre>vim /root/.bashrc</pre>

=== Colours ===

https://wiki.archlinux.org/index.php/Color_Bash_Prompt

Add these:

<pre>alias ls='ls --color=auto'
alias grep='grep --color=auto'</pre>

<pre>source /root/.bashrc</pre>

<pre>vim /root/.vimrc</pre>
<pre>syntax on</pre>

Exit your session and re-enter it.

=== Crontab editor ===

Add this line in:

<pre>EDITOR=vim; export EDITOR</pre>

<pre>crontab -e</pre>

== Binary/binaries ==

These are normally in the bin or sbin folder for a program.

== Calendar ==

<pre>apt-get install gcal
gcal -K -q GB_EN December/2012-January/2013 # Holidays for Dec/2012 and Jan/2013 with week numbers</pre>

Credit to User [http://www.commandlinefu.com/commands/by/mpb MPB]

== Check Linux version/kernel ==

cat /etc/issue

For Ubuntu do cat /etc/issue or for some CentOS distributions use cat /etc/redhat-release

<pre>uname -a
uname -r #for just the kernel
uname -rs #for OS and kernel</pre>

== Check if SELinux is enabled ==

<pre>apt-get install chkconfig
yum install chkconfig

chkconfig --list
cat /etc/sysconfig/selinux
sestatus
selinuxenabled</pre>

== Check if Virtualization is available for server ==

CentOS:

<pre>egrep '(vmx|svm)' --color=always /proc/cpuinfo</pre>

Ubuntu:

<pre>apt-get install cpu-checker
kvm-ok</pre>

== Check your PuTTY (TTY) session ==

Type this into command line:

tty

== CLI/bash Commands and scripting ==

* [http://www.cyberciti.biz/faq/unix-linux-bsd-appleosx-bash-assign-variable-command-output Assign variable command output]

* For variables with multiple pipes "|", use tacs `` instead of quotes ""
* If you are attempting to use the Unix mail function, you have to specify a body otherwise it will hang.
* If you have an if statement and its requirements are not met (e.g. greater than) and it then moves onto the next if statement, if it uses a mail function it may send it to the root user's email or the Admin/Administrator's email address. To avoid this use > /dev/null . 2>&1 likely won't work.
* It seems if you are using the read function, you can only call a variable that is inside of it (subshell), from [http://www.unixguide.net/unix/bash/E4.shtml here].
* To stop a ping after x amount of responses, do ping -c x or use ping -oc y (where y equals a maximum amount of tries)
* Use >> to append an output to the end of the file.
* The use of && means that you only echo the name of the directory if the directory creation is successful.

- The $() syntax allows you to load anything echoed to STDOUT to be loaded into a variable, and the single quotes ensure that if there are any spaces in the directory name, it still gets loaded into a single variable. To use command substitution, enclose any command that generates output to standard output inside parentheses and precede the opening parenthesis with a dollar sign, $(command). Command substitution is useful when assigning a value to a variable. It is handy for using the output of one command as an argument to another command. [http://mywiki.wooledge.org/BashFAQ/082 Why is $(...) preferred over `...` (backticks)?] . A good use of this is in http://serverkb.co.uk/tools/slow.sh

* To quote double quotes (") do the following: echo -e "Testing \"quotes\" here" - this will show as Testing "quotes"
* Quotes prevent wildcard (*) expansion.

=== $? ===

This is the exit status/code of the last executed function/program/command.

=== [http://beyondgrep.com ack] ===

To look into.

=== [http://www.grymoire.com/Unix/Awk.html Awk] ===

To '''print out a list of just folders/file'''s you want, do;

<pre>ls -l filepath | awk '{print $9;}'</pre>

This won't work correctly if there is spaces in the filename. To resolve this, use [[Linux#Find | this]] command whilst in the directory itself.

To do multiple sections of a result, do:

awk '{print $1,$2,$4,$X;}'

If you want to '''get rid of/cut certain/specific lines/rows from STDOUT''' aka '''print a specific line''', use awk in this way:

<pre>awk 'NR==22'</pre>

This is for use ''without'' a file. This example will only display the 22nd row from your output.

Notes: Blank lines count as a row. To do multiple lines do awk 'NR==22,NR==25' . This will output line 22-25.

The command sed '22 ! d' would do the same as the awk 'NR==22' example.

To '''get rid of pipe symbols in a file''', do:

awk -F'|' '{print $1,$10}' FileWithPipes > FileWithoutPipes

Alternatively if you get a list, e.g of domains from MySQL with only one column selected, put them in a file and you can remove the pipes by doing:

<pre>cat domainlist | awk '{print $2}' > list</pre>

awk '{ printf "%-20s %-40s\n", $1, $2}' allows you to '''[http://stackoverflow.com/questions/6462894/how-can-i-format-the-output-of-a-bash-command-in-neat-columns print information in columns]'''

=== Cat ===

Parse JSON file:

<pre>cat file | python .mjson.tool</pre>

=== Cut ===

This tool can be used in an example where you get an output but want to strip it to exactly what you need e.g.

lookupipscript.sh <IPaddress>

Output below:

<pre>Plan : Bronze, Silver, Gold
Type : IPv4 or IPv6
URL : http
IP : 0.0.0.0(primary)</pre>

lookupipscript.sh <IPaddress> | sed 'row ! d' | awk '{print $column;}'

This would output 0.0.0.0(primary). To get just the IP address and not the "(primary)" section, do:

| cut -c 1-7

Cut counts the first number/letter as 1, not 0.

=== eval ===

Use this of you want run a variable after a pipe and to shorten down your scripts. e.g. in http://serverkb.co.uk/tools/getdns.sh

<pre>ns="ns.nameserver.co.uk"
d="domain.co.uk"
g="grep $d | grep -v 'DiG\|;'"

echo "dig @$ns $d A"
dig @$ns $d A | eval $g</pre>

It is a good replacement instead of $() or `` or running just a variable.

=== [http://unixhelp.ed.ac.uk/CGI/man-cgi?find Find] ===

==== [http://www.cyberciti.biz/faq/linux-unix-osx-bsd-find-command-exclude-directories Exclude directories] ====

==== [http://www.cyberciti.biz/tips/linux-findinglocating-files-with-find-command-part-1.html Guide Part 1] ====

[http://content.hccfl.edu/pollock/unix/findcmd.htm Find Help] (this includes [http://www.unix.com/tips-tutorials/20526-mtime-ctime-atime.html mtime] commands)

<pre>find . -maxdepth 1 -type f -printf "%f\n" | sed s/,$//</pre>

'''Finds all files that contain "some string"'''. This command is useful in a directory (e.g. mail), so you would do ls -lah | grep year-mm then:

<pre>find . -type f -exec grep -l "some string" {} \;</pre>

=== [http://www.thegeekstuff.com/2011/07/bash-for-loop-examples for loop examples] ===

=== Functions ===

A prime use of functions is in our script to replace the date.timezone settings in php.ini at http://serverkb.co.uk/tools/phptimezone.sh

<pre>#!/bin/bash
APACHEPHP="/etc/php5/apache2/php.ini"
CURRENT="\n\nThis is the current timezone configuration:"
DONE="If the settings were wrong, they are as below now:"
ETC="/etc/php.ini"

function UBDEB(){
echo -e "\nThe operating system is Debian/Ubuntu, so editing $APACHEPHP" $CURRENT
grep "date." $1 | head -7 | grep -v '; http\|Define' ; echo ""
sed -i -e 's/;date.timezone\ =/date.timezone\ =\ \"Europe\/London\"/g' $1
sed -i -e 's/;date.default_latitude\ =\ 31.7667/date.default_latitude\ =\ 51.500181/g' $1
sed -i -e 's/;date.default_longitude\ =\ 35.2333/date.default_longitude\ =\ 0.12619/g' $1
echo $DONE
grep "date." $1 | head -7 | grep -v '; http\|Define' ; echo ""
}

function RHEL(){
echo -e "\nThe operating system is likely CentOS, editing $ETC" "$CURRENT
grep "date." $1 | head -7 | grep -v '; http\|Define' ; echo ""
sed -i -e 's/;date.timezone\ =/date.timezone\ =\ \"Europe\/London\"/g' $1
sed -i -e 's/;date.default_latitude\ =\ 31.7667/date.default_latitude\ =\ 51.500181/g' $1
sed -i -e 's/;date.default_longitude\ =\ 35.2333/date.default_longitude\ =\ 0.12619/g' $1
echo $DONE
grep "date." $1 | head -7 | grep -v '; http\|Define' ; echo ""
}

if [[ `cat /etc/issue | sed '1 ! d' | awk '{print $1;}'` == "Debian" || `cat /etc/issue | sed '1 ! d' | awk '{print $1;}'` == "Ubuntu" ]];
then
UBDEB "$APACHEPHP"
else
RHEL "$ETC"
fi</pre>

Credit to Sam Teale for helping me with this.

=== Grep ===

If you are grepping a a .gz or .zip file you generally need to use zgrep.

==== Exclude multiple directories ====

<pre>grep 'string' -R . -il --exclude="/proc" --color
grep -iR "string" * | grep -v "/proc"</pre>

==== Look for IP address ====

do this:

grep -E -o '(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)'

courtesy of [http://stackoverflow.com/questions/427979/how-do-you-extract-ip-addresses-from-files-using-a-regex-in-a-linux-shell/428086#428086 SO]

==== Multiple terms ====

Exclude using -v

<pre>grep 'chroot\|default\|fs\|fs-passwd\|httpsdocs'</pre>

'''It is important to remember to not put a \| after the last text term.'''

This can be used with tail as well.

==== Remove pipe symbols from MySQL ====

mysql -pPASSWORD admin -e"select domain from domains;" grep -v "|" > FileWithoutPipes

==== Switches/flags ====

<pre>-A after
-B before</pre>

==== Wildcards for filepaths ====

From http://unix.stackexchange.com/questions/203195/wildcards-for-filepaths-arent-working-in-grep :

<pre>* in a regex is not like a filename glob. It means 0 or more of the previous character/pattern. So your examples would be looking for a A then 0 or more B then -DEF
. in regex means "any character" so you could fix your pattern by using
grep 'AB.*DEF'</pre>

=== Head ===

If for example you do /var/qmail/bin/qmail-qstat and it prints two separate lines, do this to get just the first line:

head -1

=== [http://www.dreamsyssoft.com/unix-shell-scripting/ifelse-tutorial.php If and Else] ===

[http://tldp.org/LDP/Bash-Beginners-Guide/html/sect_07_02.html Advanced if usage]

Use -f for files, -d for directories

<pre>if [ -f $VARIABLE ]
then
parameters (e.g. echo, mkdir, touch, rm)
fi</pre>

Combine if and $? to get to do something with the exit status of the last executed command.

<pre>if [ $? -eq 0 ]; then
commands
fi</pre>

If you want to prompt for both y and Y for yes input, use:

<pre>if [[ $variable1 = y || $variable2 = Y ]];</pre>

Another example of the above if x '''or''' y is [http://www.unix.com/302444803-post5.html here]. Use || to do if = x or y.

<pre>if [[ value = x || y ]</pre>

If you get the following error when executing a bash script outside of it's directory:

[[: not found

You need to either bash /file/path/to/script or alter the syntax to use:

<pre>-eq instead of =</pre>
or
<pre>(( command )) instead of [[ command ]]</pre>

=== If value equals multiple values ===

Using the syntax above:

<pre>echo -ne "Enter a server number (1, 2 or 3): "
read ServerNo

if [[ ( $ServerNo -eq 1 ) || ( $ServerNo -eq 2 ) || ( $ServerNo -eq 3 ) ]]; then
echo "$ServerNo is a valid server, continuing."
else
echo "$ServerNo is not a valid server, exiting."
fi</pre>

=== read ===

One of the simplest uses of this command is to do it like so:

<pre>echo -ne "Enter the filename you want to create: "
read createdfilename
touch $createdfilename</pre>

=== sed ===

If you want to '''get rid of/cut certain/specific lines/rows from STDOUT''' aka '''print a specific line''', use sed in this way:

sed '22 ! d'

This is for use ''without'' a file. This example will only display the 22nd row from your output.

Notes: Blank lines count as a row. The command awk 'NR==22' would do the same.

'''To print individual/separate lines, e.g. 1, 4 and 5:'''

sed -ne '1p;4p;5p'

'''To print between lines 22 to 39:'''

sed '22,39 ! d'

'''To put a variable inside sed, use quotes instead of apostrophes:'''

sed "22,$variable ! d"

'''To delete parenthesis/brackets, use this:'''

sed 's/['''()''']//g' 
sed 's/[''')''']//g' 
sed 's/['''(''']//g' 
sed 's/['''[]''']//g' 
sed 's/[''']''']//g' 
sed 's/['''[''']//g'

==== Replace text in a file ====

sed -i -e 's/TextToFindToReplace/TextToReplaceItWith/g' filename

To handle spaces, forward slashes and quotes " ", use back slashes like you do in filenames:

sed -i -e 's/'''File\"quotes\"WithA\ Space'''/''HereIs''\/''ABackslash''/g' filename

=== sleep and usleep ===

Use sleep if you want to "wait" X seconds. usleep is measured in microseconds and cannot do more than 1 second. 100000 (100,000 / 100k) = 0.1 seconds. 1,000,000 = 1 second.

=== Shells and subshells ===

If you want a script to make changes to your current shell, not the subshell a bash script works in, execute the script by doing the following (sometimes you may need to do ./ still):

<pre>. script</pre>

This information was provided by these sources: [http://stackoverflow.com/questions/874452/change-current-directory-from-a-script 1], [http://stackoverflow.com/questions/255414/why-doesnt-cd-work-in-a-bash-shell-script 2]

=== tee ===

Tee command is used to store and view (both at the same time) the output of any other command.

Tee command writes to the STDOUT, and to a file at a time.

By default the tee command overwrites the file. You can instruct tee command to append (like >> does) to the file using the option –a as shown below.

<pre>ls | tee –a outputfile</pre>

=== [http://mywiki.wooledge.org/BashFAQ/031 Use [[ instead of [] ===

=== Variables ===

If you store a variable with a command within it as follows:

<pre>variablename=`command`</pre>

you should instead store it like this:

<pre>variablename=$(command)</pre>

And then call it as follows:

<pre>${variablename}</pre>

=== Watch ===

Example/s:

To monitor a file's size:

<pre>watch -n 1 'ls -lh | grep filename'</pre>

=== xargs ===

This can be incredibly useful if you get "Argument list too long"

cd /to/directory , find . -type f | xargs rm -Rf

If you need to remove a list of files with spaces in them, do this:

<pre>ls -lah | grep "SpecificString" | awk '{print $9,$10,$11,$etc}' | xargs -I {} rm -v {}</pre>

Use ls -lh to not include hidden files/file starting with a full stop.

For simple removal of normal files do this in a screen session:

<pre>ls -lh | awk '{print $9}' | xargs -t rm</pre>

Otherwise try using find:

<pre>find . -exec grep PATTERN {} + | wc -l</pre>

Copying multiple files:

<pre>ls -lh | grep TEXT | awk '{print $9}' | xargs cp -t /target/path/</pre>

== Compare a remote file with a local file ==

ssh user@host cat /path/to/remotefile | diff /path/to/localfile -

Credit to User [http://www.commandlinefu.com/commands/by/root Root]

=== Compare files in a directory ===

diff -bur folder1/ folder2/

Warning: when doing diff on folders, if the timestamps are different it will think the files are different. If you actually compare the files, they will be the same.

== Console Clock in corner ==

while true; do echo -ne "\e[s\e[0;$((COLUMNS-27))H$(date)\e[u"; sleep 1; done &

'''Warning, this auto scrolls your SSH session'''. To kill it, do:

ps aux | grep bash | grep -v grep

Then kill the bash session at the time you ran it:

kill <processid>

Credit to User [http://www.commandlinefu.com/commands/by/SQUIIDUX Squiidux]

 -->

== Create symlink ==

https://www.cyberciti.biz/faq/creating-soft-link-or-symbolic-link/

How to chown a symlink: https://superuser.com/questions/68685/chown-is-not-changing-symbolic-link

Old method:

<pre>ln -s TARGET LINK_NAME</pre>

== Cronjob/Crontab ==

To check a cronjob has at least attempted to run/execute, check this at the time of execution:

<pre>tail -f /var/log/syslog | grep CRON</pre>

[http://www.openjs.com/scripts/jslibrary/demos/crontab.php Generator]

<pre>crontab -e
crontab -l

* * * * * command to be executed
- - - - -
| | | | |
| | | | +----- day of week (0 - 6) (Sunday = 0 or 7)
| | | +------- month (1 - 12)
| | +--------- day of month (1 - 31)
| +----------- hour (0 - 23)
+------------- min (0 - 59)
</pre>

Guides:

http://www.adminschoice.com/crontab-quick-reference

To do a job every X minutes, do */X * * * *

To do a job every minute in a specific hour, do * X * * *

To do a job every X hours, do * */X * * *

To do a job every day at X hour on the hour, do 0 9 * * * for 9am each day.

To do a job every week at 2am on Sunday, do 0 2 * * 0

To monitor active cron jobs, do tail -f /var/log/cron

=== /usr/local/bin/php: No such file or directory ===

Do whereis php

Generally it is actually in /usr/bin/php

== Cron Daemon email ==

If you get the below email:

<pre>cd / && run-parts --report /etc/cron.daily
/etc/cron.daily/sysklogd:
chown: cannot access `/var/log/mail.warn': No such file or directory
chown: cannot access `/var/log/syslog': No such file or directory
chown: cannot access `/var/log/mail.info': No such file or directory</pre>

Do the following:

<pre>cd /var/log
touch /var/log/mail.warn /var/log/syslog /var/log/mail.info
/etc/init.d/sysklogd restart</pre>

== Date ==

=== Spaces ===

To put spaces between variables (e.g +%H%M) use single quotes:

<pre>The time is `date '+%R:%S %Y %Z'` on the following Day/Month/Year `date '+%a %b %d'`</pre>

== Echo colours ==

[http://misc.flogisoft.com/bash/tip_colors_and_formatting Tips for colours and formatting]

Place 0; for the normal version (e.g. Black is 0;30) 
Place 1; before these to get the light colour version.

Here are the colour codes:

{| border="1" align="center" style="text-align:center;" class="collapsible collapsed wikitable"
|-
! colspan="3"|
|-
|'''Colour'''
|'''Foreground'''
|'''Background'''
|-
|Black
|30
|40
|-
|Dark Grey
|1;30
|1;40
|-
|Red
|31
|41
|-
|Light Red
|1;31
|1;41
|-
|Green
|32
|42
|-
|Light Green
|1;32
|1;42
|-
|Yellow
|1;33
|1;43
|-
|Brown
|0;33
|0;43
|-
|Blue
|34
|44
|-
|Light Blue
|1;34
|1;44
|-
|Magenta (Purple)
|35
|45
|-
|Light Purple
|1;35
|1;45
|-
|Cyan
|36
|46
|-
|Light Cyan
|1;36
|1;46
|-
|White
|37
|47
|-
|Light Gray
|0;37
|0;47
|-
|}

An example:

<pre>#!/bin/bash

wipe="\033[1m\033[0m"

black="40m"
darkggrey='\E[1;30m'
red='\E[31m'
lightred='\E[1;31m'
green='\E[32m'
lightgreen='\E[1;32m'
yellow='\E[1;33m'
brown='\E[0;33m'
blue='\E[34m'
lightblue='\E[1;34m'
purple='\E[35m'
lightpurple='\E[1;35m'
cyan='\E[36m'
lightcyan='\E[1;36m'
white='\E[37m'
lightgray='\E[0;37m'
green='\E[32m;'</pre>

<pre>echo -e "$green$black"
echo Hello World
echo -e "$wipe"</pre>

or

<pre>echo -e "Output a ${green}coloured${wipe} word."</pre>

<pre>./colourtest.sh

Hello World</pre>

The Hello World text appears green.

== Execute one off command whenever ==

echo "ls -l" | at midnight

This is an alternative to cron which allows a one-off task to be scheduled for a certain time.

Credit to User [http://www.commandlinefu.com/commands/by/root Root]

== File Locations (index priority) ==

/etc/apache2/mods-enabled/dir.conf (on Ubuntu) or /etc/httpd/conf/httpd.conf (on CentOS, ~line 402) and it should show something like:

<pre>DirectoryIndex index.html index.html.var index.shtml index.cfm index.php index.htm</pre>

This shows the default priority in which the index page is picked up and this can be set in the [[.htaccess]] file as well with:

<pre>DirectoryIndex index.html index.php</pre>

These are good places to check if you are using all of your [[Resource_Usage|disk space]].

cd /var/log 
cd /var/www/vhosts (website and statistics) 
cd /var/lib/mysql (database) or mysql/mysql 
cd /usr/bin/mysqldump (mysql dump) 
cd var/qmail (mail logs, queue and configuration) 
cd /var/lib/psa/dumps (physical Plesk backups) 
cd opt/psa/tmp/ (Plesk stores temporary files here for backups)

== File Permissions ==

[http://linuxcommand.org/lts0070.php One of the best permissions guide]

The values and their equivalent permissions. R is Read, W is Write and X is Execute. There are three sets on a file or folder (e.g. -rwx-w--w- , -rw-r--r-- , -rwxr-xrwx) so you need to put in a value of three (or four in rare occasions) for a file/folder e.g. 644.

<pre>0 --- 
1 --x
2 -w-
3 -wx
4 r--
5 r-x
6 rw-
7 rwx</pre>

'''The syntax for chmod is (for example) 755 fileorfolder. The -R option can also be used to set the permissions on anything below a folder.''' 
'''The syntax for chown is chown user:group fileorfolder . To apply the user:group to anything below a folder you need to use the -R option.'''

[http://permissions-calculator.org/ Permissions Calculator] 
[http://www.tuxfiles.org/linuxhelp/filepermissions.html Help Guide 1] 
[http://www.freeos.com/articles/3127?page=3 Help Guide 2] 
[http://en.wikipedia.org/wiki/Filesystem_permissions#Notation_of_traditional_Unix_permissions Unix Notation] 
[http://www.faqs.org/docs/linux_intro/sect_03_04.html File protection with chmod]

If you use PHP Support as '''Apache module, it will use the third value of''' -rw- r-- '''r-x''' to permissions. If it is using '''Fast CGI it will use the user:group''' for the first two values '''-rwx rw-''' --x

If you are using Plesk a good place to check if you are getting Forbidden errors on your website is /var/www/vhosts/yourdomain.com/httpdocs/statistics/logs/error_log . Access your site and tail -f that file. If you get .htaccess pcfg_openfile: unable to check htaccess file, ensure it is readable name your .htaccess file correctly, set your httpdocs to 757 and see [http://serverfault.com/questions/61726/permission-denied-home-htaccess-pcfg-openfile-unable-to-check-htaccess-file this link].

'''Special permissions'''

There is also a, g & s which are not widely used as it just needs additional representation at the special/setid permission to the group.

To set a file to -rws--x--x for example use

<pre>4 = setuid - s
2 = setgid - s
4 + 2 = S
1 = Sticky Bit
4 + 2 + 1 = T
2511 -r-x--s--x (e.g. /var/qmail/bin/qmail-remote or /var/qmail/bin/qmail-queue)
4655 -rwSr-xr-x
4711 -rws--x--x
4744 -rwsr--r--
4755 -rwsr-xr-x
6411 -r-S--s--x.
6511 -r-s--s--x
6644 -rwSr-Sr--
6666 -rwSrwSrw-
7000 ---S--S--T
7644 -rwSr-Sr-T
7711 -rws--s--t
7744 -rwsr-Sr-T
7755 -rwsr-sr-t</pre>

[http://serverfault.com/questions/111350/what-chmod-and-ownergroup-settings-are-best-for-a-web-application Owner and Group advice for websites]

== [http://adminlogs.info/2011/06/02/linux-find-command-tips Find command guide] ==

== [http://serverfault.com/questions/35076/need-to-fix-file-permissions-in-a-users-home-directory Fix file and folder permissions easily] ==

== FreeBSD ==

* mysqldump location: /mysql/bin/mysqldump
* Remove syntax:

- rm -r folderName
* Generic tunneling interface starts with gif

=== [http://forums.freebsd.org/showthread.php?t=5852 Check software versions] ===

=== fetch instead of wget ===

To download a file.

=== whereis instead of locate command ===

To find files/folders.

== Full Directory listing ==

<pre>apt-get install tree
yum install tree
tree > tree.txt</pre>

If you feel adventurous do cat tree.txt , it will take a while ;)

=== Find the deepest directory in your server/file structure ===

<pre>find . -type d -printf '%d:%p\n' | sort -n | tail -1</pre>

=== Find and remove specific file types from current directory ===

<pre>cd into the directory
find . -type f -name '*.filetype' -exec rm -v {} \;</pre>

=== Line count a file ===

wc -l /file/path

== Generate random number ==

Between 1 and 10:

seq 10| shuf | head -1

== GeoIP - Block countries accessing website ==

Ubuntu: apt-cache search geoip ; apt-get install geoip-database libgeoip-dev libgeoip1 python-geoip geoip-bin libapache2-mod-geoip tclgeoip 
CentOS: yum list |grep -i geo , yum install GeoIP.x86_64 
http://www.webhostingtalk.com/showthread.php?t=959646 
http://askmatt.co.uk/blog/2010/05/block-countries-using-apache-mod-geo-ip-list-of-countries-by-fraud-risk

== Gunzip and Zip ==

To gzip a file (.gz) up, do:

<pre>gzip file</pre>

The above won't work for folders.

Or if zip is installed:

<pre>zip -r filename.zip filename</pre>

To unzip a .gz file, do:

<pre>gunzip file</pre>

To extract a .tgz file, do:

<pre>tar zxvf fileNameHere.tgz</pre>

See http://serverkb.co.uk/wiki/Linux#tar_command for further details.

== [http://eng.eelcowesemann.nl/plesk/changing-the-servers-hostname-in-plesk Hostname guide] (rough) ==

If the server runs Plesk and Virtuozzo, the permanent one needs setting on the hardware or in Virtuozzo.

Run dig -x IP.IP.IP.IP from any Linux server and it will show you the PTR/hostname.

'''Note:''' Most servers by default come with a non resolving hostname of localhost, localhost.localdomain or something generic.

The hostname should never be left as the default value on a server sending mail, as it is one of three things mail recipient's mailservers see to determine if mail is spam or not. The other two are reverse DNS and the SMTP banner.

If Plesk throws an error when clicking Websites & Domains tab regarding hostname -f, see [[Plesk_Errors#Domains_area_is_blank | this resolution]].

== How to fix broken packages ==

Run the following commands below:

<pre>dpkg --configure -a
apt-get install -f
#or
apt-get -f install</pre>

If the problem still exists, then edit dpkg status file:

<pre>gksudo gedit /var/lib/dpkg/status</pre>

Find the package in question, and remove everything that has anything to do with it and save the file.

== How to install .deb files ==

<pre>dpkg -i filename.deb</pre>

== [[.htaccess]] ==

[http://en.wikipedia.org/wiki/Htaccess HyperText access]

== [http://stackoverflow.com/questions/653096/howto-free-inode-usage inode usage] ==

<pre>df --si
df -ih</pre>

A lot of the time the cause can be /tmp (/var/lib/php/session/ on Plesk) due to sessions. You may want to delete the files in there.

== Investigating high load ==

If you are getting a high load average in top, these are some of the steps you can take to investigate the issue.

Check which process has the most open of itself:

<pre>ps aux | awk '{print $11}' | sort | uniq -c | sort -nk1 | tail -n5</pre>

Stop that process, then run the above command a second time. Then start it again and run the command a third time.

=== Useful software ===

* top
* htop
* iotop

All these will do the job. Firstly check the CPU wait time, this is shown within top in Cpu(s): 8.0%us, 2.8%sy, 0.0%ni, 40.7%id, 48.3%wa

<pre>%wa in</pre>

If this is high, check the Status column (S column in top) to see if any are labelled D. The [http://stackoverflow.com/questions/666783/how-to-find-out-which-process-is-consuming-wait-cpu-i-e-i-o-blocked processes blocked on IO] are the ones marked as D.

=== On a Plesk server ===

Ensure sites are running PHP as Fast CGI Application instead of Apache module so you can see which USER the process is running as. Pressing the letter "c" on your keyboard will show the path and normally the website name.

<pre>wget http://serverkb.co.uk/tools/memcpu.sh ; chmod +x memcpu.sh ; ./memcpu.sh > usage.log &
tail -f usage.log</pre>

You can alter the PHP Handler on Plesk boxes in the psa database easily by doing:

<pre>mysql -uadmin -p`cat /etc/psa/.psa.shadow`;
use psa
select * from hosting\G
select dom_id,www_root,php_handler_type from hosting;
update hosting set php_handler_type="module" where dom_id=x;</pre>

If sites run PHP as an Apache module scripts will execute as the Apache user www-data, this can make it difficult to see which site they belong to. This also means scripts run with privileges of the Apache user so if an account is compromised an attacker can get access to all other accounts. Also running as Apache module can make the Apache process CPU report look artificially high. Running PHP as Fast-CGI executes scripts as an FTP user associated with each subscription allowing easier identification of problem scripts and limit the damage of rogue scripts.

CPU reports are not an easy way to determine server health. We'd recommend you look at changes and trends rather than the absolute numbers. Most importantly consider your real world performance.

== Linux Container ==

This install below is for an Ubuntu physical server, I may update this in the future for CentOS, Fedora and others.

https://help.ubuntu.com/12.04/serverguide/lxc.html

If you need to get file off the container, you can just scp it off. If the recipient server is slow, try moving the file to the host machine by doing:

scp -Psshport file root@hostIPaddress:~

=== Installation of LXC ===

<pre>apt-get install lxc
cat /etc/init/lxc-net.conf | grep USE_LXC_BRIDGE</pre>

If true set to false unless you want the containers to NAT to your servers real IP addresses, and to be accessible externally.

=== Pre-container creation steps ===

To reduce errors pre-container creation do the following:

<pre>dpkg-reconfigure locales
locale-gen en_GB
update-locale LANG=en_GB.UTF-8</pre>


=== Creating/deleting containers ===

[http://wiki.openvz.org/Download/template/precreated OpenVZ Template list]

Check the templates below and pick one:

<pre>cd /usr/lib/lxc/templates/ ; ls -lah</pre>

Create a container from one of the templates:

<pre>lxc-create -t ubuntu -n NameOfTheContainer</pre>

If you want to install the fedora package, do apt-get install yum

To delete it just do:

<pre>lxc-destroy -n NameOfTheContainer</pre>

=== Start/stop a container ===

<pre>lxc-start -n NameOfTheContainer -d</pre>

/etc/init.d/lxc stop

=== Access the container ===

The default user is 'ubuntu' with the password 'ubuntu', to enter a container, do:

<pre>lxc-console -n NameOfTheContainer
sudo -i</pre>

Exit using Ctrl + a, then press q

To re-enter the container, do lxc-console -n NameOfTheContainer and then press enter (you may have to a few times)

'''Access externally:'''

iptables -t nat -A PREROUTING -p tcp --dport 2222 -j DNAT --to 10.0.3.61:22

'''Make sure you remove this rule afterwards and DO NOT reboot your server.'''

=== Configuration settings ===

* By default you can ping a container from the host, and vice versa, and you can ping the outside world from the container.
* You can set the hostname just like a normal server, if you want to rename the container.

==== Default configuration of system files ====

<pre>cd /var/lib/lxc/nameofcontainer/rootfs/etc/sysconfig/network-scripts
vim ifcfg-eth0</pre>
<pre>DEVICE=eth0
BOOTPROTO=dhcp
ONBOOT=yes
HOSTNAME=phptester
NM_CONTROLLED=no
TYPE=Ethernet
MTU=</pre>

<pre>vim /var/lib/lxc/nameofcontainer/config</pre>
<pre>lxc.network.type=veth
lxc.network.link=lxcbr0
lxc.network.flags=up
lxc.network.hwaddr = MAC Address
lxc.utsname = MT</pre>

<pre>vim /etc/lxc/lxc.conf</pre>
<pre>lxc.network.type=veth
lxc.network.link=lxcbr0
lxc.network.flags=up</pre>

You can add the below to /etc/network/interfaces

<pre>auto br1
iface br1 inet dhcp
bridge_ports eth0</pre>

==== Fedora ====

The mirrors/repositories the container uses may be broken by default, don't try to install anything. You'll likely get:

''Error: Cannot retrieve repository metadata (repomd.xml) for repository: fedora. Please verify its path and try again''

And you likely won't be able to ping anything except the host machine and localhost/127.0.0.1

iptables -t nat -A POSTROUTING -s ContainerIP/24 -j SNAT --to-source PhysicalHostIP 
iptables -t nat -A PREROUTING -m tcp -p tcp --dport 10022 -j DNAT -i eth0 --to-destination ContainerIP:80 
iptables -t nat -A PREROUTING -m tcp -p tcp --dport 10443 -j DNAT -i eth0 --to-destination ContainerIP:443

[https://www.berrange.com/posts/2011/09/27/getting-started-with-lxc-using-libvirt libvirt]

<pre>vi /etc/yum.repos.d/fedora.repo
vi /etc/yum.repos.d/fedora-updates.repo</pre>

Uncomment (#) the lines starting with "baseurl"

yum update

==== OpenSUSE ====

[http://en.wikipedia.org/wiki/OpenSUSE#Version_history Version history]

http://www.lacerta.be/d7/content/opensuse-lxc-container-inside-ubuntu

=== List containers ===

lxc-list

=== Set passwords ===

Log in as the root user of the container:

'''Fedora''' container:

<pre>Username: root
Password: root</pre>

Set the root password to something different:

<pre>passwd</pre>

You will need to do yum install vim when inside the server.

'''Ubuntu''' container:

<pre>sudo -i
Username: ubuntu
Password: ubuntu</pre>

Set the user's password:

<pre>passwd ubuntu</pre>

Set the root user's password:

passwd

=== SSH in externally ===

'''To route from externally through the host to the container, just do the below iptables rule''':

<pre>iptables -t nat -A PREROUTING -p tcp --dport 1337 -j DNAT --to 10.0.4.60:22
iptables-save</pre>

In the above case we are saying:

- You want to SSH in on port 1337 
- The container's eth0 IP address is 10.0.4.60 
- Then below we are saying the physical machine has an IP address of 110.111.112.113

Then externally from the server do:

<pre>ssh root@110.111.112.113 -p2222</pre>

And bingo! You should be in the container.

<pre>passwd</pre>


== [http://wiki.debian.org/LSBInitScripts LSB Init Scripts] ==

== ls list only directories or files ==

Directories:

<pre>ls -lad */</pre>

Files:

<pre>ls -la | grep -v ^d</pre>

== Kill tty session ==

<pre>w
ps aux | grep bash | grep -v grep
ps aux | grep tty | grep -v grep
kill -HUP <processid></pre>

[http://www.cyberciti.biz/faq/howto-kill-unix-linux-user-session Further info]

== Maldet ==

[http://www.rfxn.com/projects/linux-malware-detect Documentation] 
[http://www.rfxn.com/downloads/maldetect-current.tar.gz Maldet .tar.gz] 
[http://blog.hostonnet.com/how-to-install-and-configure-maldet-linux-malware-detect-lmd Install and Configure]

<pre>cd /root ; wget http://serverkb.co.uk/tools/maldet.sh ; chmod +x maldet.sh ; ./maldet.sh</pre>

Always run your scans from chroot environment (if it has one/is possible) and in Screen (screen -S NameIt), and detach by doing CTRL + A, then press D

Scan reports are normally stored in /usr/local/maldetect/sess/ as session. files.

maldet -a -e -l filepath

== Manually alter time/date ==

'''Ubuntu'''

<pre>date
date mmddtimeyear #as seen below</pre>

'''Cent OS'''

<pre>cd /etc/
ls -lah
rm localtime
ln -s /usr/share/zoneinfo/Europe/London /etc/localtime
date mmddtimeyear
| | | | ---> 2012
| | | 24hr --> XX:XX without :
| | dd -------> day
| mm ---------> month

/etc/init.d/ntpd restart or start
date</pre>

== Move files into your home directory not owned by your own user ==

Copy to /var/tmp or /tmp (for small files) and do:

<pre>chmod ugo+rw <filename></pre>

== PID ==

Under construction.

Process ID.

To determine the usage of a specific process, do top -p PID

The maximum number of pids can be obtained from /proc/sys/kernel/pid_max

== .profile ==

Put this in .profile file for on user startup:

<pre>echo "" ; df -h | sed -ne '1p;5p' ; echo "rootfs"
echo "" ; free -m
echo "" ; w | head -1 | sed 's/^ *//g'
echo "" ; w | tail -10 | grep -v average ; echo ""</pre>

== Proxmox ==

To access via the web go to https://IPaddress:8006

Rough notes:

apt-get install sudo

Proxmox

/var/lib/vz

dump is for backups 
images is for OS images 
private is for OpenVZ container file systems 
template/cache is for OpenVZ templates

http://openvz.org/Download/template/precreated

Create VM creates KVM 
Create CT creates OpenVZ container 

vzctl enter id 
vzctl start/stop id 

iptables -t nat -A POSTROUTING -o vmbr1 -j MASQUERADE 
restart networking on host and CT

=== cman_tool: Cannot open connection to cman ===

<pre>pvecm status
pvecm nodes
cman_tool: Cannot open connection to cman, is it running ?</pre>

<pre>service pve-cluster restart
pvecm delnode NodeName</pre>

=== Force remove an OpenVZ container ===

<pre>vzctl stop 100 ; vzctl destroy ContainerID
cd /var/lib/vz/private
rm ContainerIDfolder -R
cd /var/lib/vz/root
rm ContainerIDfolder -R
cd /etc/pve/nodes/ContainerName/openvz
mv ContainerID.conf ContainerID.bak</pre>

Make sure it does not exist in cat /etc/pve/.members

=== Remount a logical partition/volume ===

lvdisplay

/dev/mapper/pve-data /var/lib/vz (this will be different in your file system)

=== Unable to get local IP address ===

<pre>/etc/init.d/pve-cluster restart
service pve-cluster start
Starting pve cluster filesystem : pve-cluster[main] crit: Unable to get local IP address
(warning).</pre>

Make sure in /etc/hosts your domain name resolves to the server and you also have it without the .co.uk/.com etc in the file as so:

<pre>ServerIPaddress domain.co.uk domain pvelocalhost
127.0.0.1 localhost localhost.localdomain</pre>

Then do:

<pre>/etc/init.d/hostname.sh stop
/etc/init.d/hostname.sh start
service pve-cluster start</pre>

=== Transport endpoint is not connected ===

<pre>df -h
df: `/etc/pve': Transport endpoint is not connected</pre>

<pre>ls -lah /etc/pve
ls: cannot access pve: Transport endpoint is not connected
d????????? ? ? ? ? ? pve</pre>

Do this:

<pre>umount /etc/pve
pvecm status</pre>

You will get:

unable to get IP for node 'hostname' - node offline?

The fix is the same as [[Linux#Unable_to_get_local_IP_address | this]] one, ensure you have the domain without the web extension in /etc/hosts resolving to the servers IP address. Then do:

service pve-cluster start

== Recover deleted files ==

You need to install this software before you delete any files:

<pre>apt-get install foremost</pre>

Then see this documentation:

https://help.ubuntu.com/community/DataRecovery 
http://ddailygirl.wordpress.com/2010/08/17/recovering-files-after-rm-in-linux 
http://www.howtoforge.com/recover-deleted-files-with-foremost 
http://www.webupd8.org/2009/03/recover-deleted-files-in-ubuntu-debian.html

== Remove file starting with dash ==

<pre>rm -- -filename</pre>

Remove folder starting with dash

<pre>rm -rf -- -folder/</pre>

== Remove/rename file called tilde ==

<pre>mv '~' newfilename
rm '~'</pre>

== Restart service or service ==

Useful for differently named ones, e.g.

[ -f /etc/init.d/mysqld ] && service mysqld restart ; [ -f /etc/init.d/mysql ] && service mysql restart

[ -f /etc/init.d/httpd ] && service httpd restart ; [ -f /etc/init.d/apache2 ] && service apache2 restart

== Roughly list file count ==

This includes nested directories:

<pre>find /full/file/path -type f | wc -l</pre>

== SCP Command - Secure Copy ==

To secure copy a file from one Linux server to another, use the following syntax form:

<pre>scp -P PORT file user@IPAddress:/filepath</pre>

For example:

<pre>scp -P 22 index.html root@127.0.0.1:/</pre>

To move a folder, put -r in between the port and the file(s)/folder(s) like so:

<pre>scp -P 22 -r testdirectory/ root@127.0.0.1:/</pre>

If you receive the following error while trying to SCP a file from one server to the other:

<pre>stdin: is not a tty</pre>

You can solve the issue quickly by doing the following on the destination server:

<pre>vi ~/.bashrc

if [ $(expr index "$-" i) -eq 0 ]; then
return
fi</pre>

== Screen ==

Re-join screen session

<pre>screen -r</pre>

or

<pre>screen -D -r '1234.somescreensession'</pre>

A better alternate is [[Linux#tmux | tmux]].

[http://www.ubuntugeek.com/screen-manages-multiple-sessions-on-one-terminal.html#more-1415 Manage Multiple sessions in one Terminal] 
[http://www.samsarin.com/blog/2007/03/11/gnu-screen-working-with-the-scrollback-buffer Scrollback] (vim /home/.screenrc + defscrollback 1000) 
[http://polishlinux.org/howtos/screen-tips-tricks Tips and Tricks]

== Setting the time ==

http://geoffhankerson.com/node/112 
http://codeghar.wordpress.com/2007/12/06/manage-time-in-ubuntu-through-command-line/

== Standard redirection ==

http://www.xaprb.com/blog/2006/06/06/what-does-devnull-21-mean/

STDIN, STDOUT and STDERR.

0, 1 and 2

1>/dev/null 
2>/dev/null

== sudo ==

If you exit out of root access and want to run the last command you entered without authentication, do:

<pre>sudo !!</pre>

== System Logs and Shutdown troubleshooting ==

If you are having an issue, a reboot should not be performed if the server can be accessed in any way (e.g. locally in the data centre, only if it is a Dedicated server). This is because after a reboot there is little you can find out from the logs as the important logs get cleared on restart.

<pre>last reboot
last</pre>

Do this to check which files exist:

ls -lh /var/log/syslog ; ls -lh /var/log/kern.log ; ls -lh /var/log/dmesg ; ls -lh /var/log/messages

Then do one or more of these depending on which exist:

grep -i error /var/log/syslog ; grep -i panic /var/log/syslog ; grep -i warning /var/log/syslog 
grep -i error /var/log/dmesg ; grep -i panic /var/log/dmesg ; grep -i warning /var/log/dmesg 
grep -i error /var/log/kern.log ; grep -i panic /var/log/kern.log ; grep -i warning /var/log/kern.log 
grep -i error /var/log/messages ; grep -i panic /var/log/messages ; grep -i warning /var/log/messages

errpt may show an error report on some Unix OS'.

To find .log files, run [[Linux#updatedb_.28locate_command.29 | updatedb]] and then locate *.log

To restart and [http://go2linux.garron.me/reboot-check-disks-for-errors-avoid-force-fsck on boot do a disk check] do (or -rF):

<pre>shutdown -Fr now</pre>

== [http://www.pendrivelinux.com/how-to-open-a-tar-file-in-unix-or-linux tar command] ==

To archive and compress a folder/files do:

<pre>tar -czvf files.tgz files/
tar -czvf folder.tar.gz folder/
tar cvf mubackup.tar mu/ ; gzip -9 mubackup.tar

#.tgz is same as .tar.gz</pre>

c creates the archive (tar), z compresses it into the gzip, v is verbose, f is the file/folder

To extract do:

<pre>#for tar
tar xvf file.tar

#for .tgz or tar.gz
tar zxvf file.tar.gz</pre>

[http://www.fluidthoughts.com/howto/tar-gzip/ Guide 1] 
[http://www.thegeekstuff.com/2010/04/unix-tar-command-examples/ Guide 2] 
[http://superuser.com/questions/305128/how-to-specify-level-of-compression-when-using-tar-zcvf 3] and [http://superuser.com/questions/156207/untar-ungz-gz-tar-how-do-you-remember-all-the-useful-options 4]

For bz2 files, use:

<pre>tar -xvjpf file</pre>

== top ==

The TIME column in top is displayed in minutes:seconds.hundredths

== tmux ==

C-c is CTRL+C 
C-m is ENTER

=== New session ===

Latest:

<pre>tmux new -s session_name</pre>

Also possible:

<pre>tmux new-session -s session_name</pre>

Old:

<pre>tmux new-session -n NameTheSession</pre>

=== Detach from a session ===

<pre>CTRL +B then D</pre>

=== Kill session ===

<pre>tmux kill-session -t myname</pre>

If this fails and it says:

"''session not found''"

Do the following:

<pre>tmux ls
tmux kill-session -t X</pre>

- where X is the number of the session on the left.

=== List sessions available ===

<pre>tmux ls</pre>

=== Re-attach to session ===

<pre>tmux attach
tmux attach -t ID or NameTheSession</pre>

=== Remotely execute a command ===

<pre>tmux send-keys -t ID "command" ENTER</pre>

== User ID 99 ==

This is most commonly the user nobody. This can be caused by PHP or done on purpose. cat /etc/passwd | grep 99 ; vim /etc/passwd

== User is not in the sudoers file ==

If you try to sudo into a server or run sudo and get the following message:

"''is not in the sudoers file. This incident will be reported.''"

Do the following command as root and add the username into the file in the same format as the root user:

visudo

== Use unusual characters in filenames ==

If you want to specify a space, lets say the file = /usr/local/etc/'''testingdatabase.sql'''

You need to name the file/folder as follows:

<pre>mv /usr/local/etc/testingdatabase.sql /usr/local/etc/testing\ database.sql</pre>

This will make the file be '''testing database.sql''' , on command line this will appear as '''testing\ database.sql''' .

A backslash symbol \ needs to be used before an apostrophe ' , bracket (), exclamation/bang ! symbol or question marks ?:

<pre>01\ -\ It\'s\ You.txt
#How it appears: 01 - It's You.txt

02\ -\ Boom\!.m3u
#How it appears: 02 - Boom!.m3u

03\ -\ Why\ Wont\ You\ Work\?.sh
#How it appears: 03 - Why Wont You Work?.sh

04\ -\ Musical\ Playlist\ For\ $VPS$\ Server.m3u
#How it appears: 04 - Musical Playlist For (VPS) Server.m3u</pre>

== updatedb (locate command) ==

This command is used when you cannot '''locate''' a file and you get "''locate: warning: database /var/lib/slocate/slocate.db' is more than 8 days old''". It is advised to run updatedb '''at least once a month'''. However if you get the following error when using it:

<pre>updatedb: fatal error: load_file: Could not open file: /etc/updatedb.conf: No such file or directory</pre>

You need to create or edit this file

<pre>vim /etc/updatedb.conf</pre>

and put the following inside of it:

PRUNE_BIND_MOUNTS="yes"PRUNEPATHS="/tmp /var/spool /media"PRUNEFS="NFS nfs nfs4 rpc_pipefs afs binfmt_misc proc smbfs autofs iso9660 ncpfs coda devpts ftpfs devfs mfs shfs sysfs cifs lustre_lite tmpfs usbfs udf"

Alternatively run the below script after reading this file http://serverkb.co.uk/tools/README.txt:

http://serverkb.co.uk/tools/updatedbscript.sh

To vim a file you locate, see [http://stackoverflow.com/questions/8228831/why-does-locate-filename-xargs-vim-cause-strange-terminal-behaviour this]. vim $(command)

=== Cannot find an existing file ===

Ensure that the directory path of the file that '''does''' exist is not in the following section in /etc/updatedb.conf:

<pre>PRUNEPATHS="/tmp /var/spool /media"</pre>


== vim ==

To make a copy the line below where you cursor is, hold CTRL + e. Then put a hash (comment) in front of this line. This is useful for backing up an old value before changing it.

=== Create backup of file whilst in vim ===

<pre>vim file
:!cp % %-</pre>

Press enter and continue to edit

Credit to User [http://www.commandlinefu.com/commands/by/mpb MPB]

=== Enter Insert mode ===

Press the letter i (I)

=== Enter Replace mode ===

Press the letter r (R)

=== E21: Cannot make changes, 'Modifiable' is off ===

<pre>:set modifiable</pre>

=== Search in file for multiple terms ===

Go to search mode i.e. type '/' and then type \v followed by the words you want to search separated by '|' (pipe).

Example:

<pre>/\vword1|word2|word3</pre>

Go to search mode and type the words you want to search separated by '\|'.

Example:

<pre>/word1\|word2\|word3</pre>

The first way puts you in the regular expression mode so that you do not need to put any extra back slashes before every pipe or other delimiters used for searching.

=== See changes made before exiting ===

<pre>:w !diff % -</pre>

=== Editing a jar/zip file ===

(zip#Write) sorry, your system doesn't appear to have the zip pgm

1) Check zip is installed

2)

<pre>:set modifiable
:set write</pre>

3)

E382: Cannot write, 'buftype' option is set

Check if the file has -e on it using:

<pre>lsattr filename</pre>

If so, you likely cannot edit it.

4)

Alternatively, download the file (e.g. a jar) and use an Archive tool like 7-zip to edit it.

== [http://www.cymru1.net/linux-vps/vps-hints-and-tips.php VPS Hints and Tips] ==

To check for the filepath of a command run top and then press c.

If it is a container on a node, there are generally no datacentre / rack level restrictions as the container is virtualised on a node. The only restrictions are what is put in place via the container itself effectively.

To list all open Internet, x.25 (HP-UX), and UNIX domain files, use:

lsof -i -U

== WHOIS script ==

[http://www.ivarch.com/programs/pv.shtml Pipe Viewer], [http://linux.die.net/man/1/pv PV info page]

<pre>apt-get install pv ; cd /var/www/vhosts ; ls -l | awk ' {print $9}' > domainlist ; wget serverkb.co.uk/tools/findregistrar.sh ; chmod +x findregistrar.sh</pre>

For CentOS use yum -y install jwhois.x86_64

Edit the file and replace domain registrar with the one you want to find. Then do:

<pre>./findregistrar.sh</pre>

== write error ==

If you get the following error when doing write user TTYsession or write user Session:

write: write: you have write permission turned off.

Do this to fix the problem:

mesg y

== [http://linuxcommand.org/writing_shell_scripts.php Writing Shell Scripts] ==

Linux

2018-09-18T12:20:21Z

Rootadminacc: /* tmux */

To check your server info, do lscpu 
To run a bash script without executing it, do bash -n scriptname.sh 
To see help commands do command --help or man command. To paste into PuTTY, use SHIFT + INSERT. 
For detailed software and hardware info do apt-get install hardinfo then hardinfo. For CentOS 6 use [http://pkgs.repoforge.org/hardinfo/hardinfo-0.5.1-1.el6.rf.x86_64.rpm this]. 
To write to a user in the same SSH server, do w, get their tty session and then do write user ttySession. If they are root, do write root Session 
[http://www.linuxfocus.org/English/September1999/article103.html Awk introduction], [http://tldp.org/LDP/Bash-Beginners-Guide/html/sect_07_01.html If manual].

== Append date to same line ==

Either of these will work:

<pre>| awk '{ print strftime("%Y-%m-%d %H:%M:%S"), $0; }'
| ts '%F %T'</pre>

To customise date, put a + symbol in front of the flag:

<pre>date +%R
14:32</pre>

To get this format of the date/time:

24 May 2013 10:25:33

Use:

<pre>date +%d\ %B\ %Y\ %H:%M:%S</pre>

== authorized_keys (RSA) ==

This will show you how to SCP, SSH and rSync without prompting for password between two servers.

Whenever you need to use SCP to copy files, it asks for passwords. Same with rSync as it (by default) uses SSH as well. Usually SCP and rSync commands are used to transfer or backup files between known hosts or by the same user on both the hosts. It can get really annoying the password is asked every time. I even had the idea of writing an expect script to provide the password. Of course, I didn't. Instead I browsed for a solution and found it after quite some time. There are already a couple of links out there which talk about it. I am adding to it...

Lets say you want to copy between two hosts host_src and host_dest. host_src is the host where you would run the SCP, SSH or rSync command, irrespective of the direction of the file copy!

On host_src, run this command as the user that runs SCP/SSH/rSync

<pre>ssh-keygen -t rsa</pre>

This will prompt for a passphrase. Just press the enter key. It'll then generate an identification (private key) and a public key. Do not ever share the private key with anyone! ssh-keygen shows where it saved the public key. This is by default ~/.ssh/id_rsa.pub:

Your public key has been saved in <your_home_dir>/.ssh/id_rsa.pub

Transfer the id_rsa.pub file to host_dest by either FTP, SCP, rSync or any other method.

On host_dest, '''login as the remote user which you plan to use when you run SCP, SSH or rSync on host_src'''.

Make sure the folder ~/.ssh exists first, if not do:

<pre>mkdir ~/.ssh</pre>

Copy the contents of id_rsa.pub to ~/.ssh/authorized_keys

<pre>cat id_rsa.pub >>~/.ssh/authorized_keys
chmod 700 ~/.ssh/authorized_keys</pre>

If this file does not exists, then the above command will create it. Make sure you remove permission for others to read this file. If its a public key, why prevent others from reading this file? Probably, the owner of the key has distributed it to a few trusted users and has not placed any additional security measures to check if its really a trusted user.

Note that SSH by default does not allow root to log in. This has to be explicitly enabled on host_dest. This can be done by editing /etc/ssh/sshd_config and changing the option of PermitRootLogin from no to yes. Don't forget to restart SSHD so that it reads the modified config file. Do this only if you want to use the root login.

Well, thats it. Now you can run SCP, SSH and rSync on host_src connecting to host_dest and it won't prompt for the password. Note that this will still prompt for the password if you are running the commands on host_dest connecting to host_src. You can reverse the steps above (generate the public key on host_dest and copy it to host_src) and you have a two way setup ready!

== .bashrc ==

<pre>vim /root/.bashrc</pre>

=== Colours ===

https://wiki.archlinux.org/index.php/Color_Bash_Prompt

Add these:

<pre>alias ls='ls --color=auto'
alias grep='grep --color=auto'</pre>

<pre>source /root/.bashrc</pre>

<pre>vim /root/.vimrc</pre>
<pre>syntax on</pre>

Exit your session and re-enter it.

=== Crontab editor ===

Add this line in:

<pre>EDITOR=vim; export EDITOR</pre>

<pre>crontab -e</pre>

== Binary/binaries ==

These are normally in the bin or sbin folder for a program.

== Calendar ==

<pre>apt-get install gcal
gcal -K -q GB_EN December/2012-January/2013 # Holidays for Dec/2012 and Jan/2013 with week numbers</pre>

Credit to User [http://www.commandlinefu.com/commands/by/mpb MPB]

== Check Linux version/kernel ==

cat /etc/issue

For Ubuntu do cat /etc/issue or for some CentOS distributions use cat /etc/redhat-release

<pre>uname -a
uname -r #for just the kernel
uname -rs #for OS and kernel</pre>

== Check if SELinux is enabled ==

<pre>apt-get install chkconfig
yum install chkconfig

chkconfig --list
cat /etc/sysconfig/selinux
sestatus
selinuxenabled</pre>

== Check if Virtualization is available for server ==

CentOS:

<pre>egrep '(vmx|svm)' --color=always /proc/cpuinfo</pre>

Ubuntu:

<pre>apt-get install cpu-checker
kvm-ok</pre>

== Check your PuTTY (TTY) session ==

Type this into command line:

tty

== CLI/bash Commands and scripting ==

* [http://www.cyberciti.biz/faq/unix-linux-bsd-appleosx-bash-assign-variable-command-output Assign variable command output]

* For variables with multiple pipes "|", use tacs `` instead of quotes ""
* If you are attempting to use the Unix mail function, you have to specify a body otherwise it will hang.
* If you have an if statement and its requirements are not met (e.g. greater than) and it then moves onto the next if statement, if it uses a mail function it may send it to the root user's email or the Admin/Administrator's email address. To avoid this use > /dev/null . 2>&1 likely won't work.
* It seems if you are using the read function, you can only call a variable that is inside of it (subshell), from [http://www.unixguide.net/unix/bash/E4.shtml here].
* To stop a ping after x amount of responses, do ping -c x or use ping -oc y (where y equals a maximum amount of tries)
* Use >> to append an output to the end of the file.
* The use of && means that you only echo the name of the directory if the directory creation is successful.

- The $() syntax allows you to load anything echoed to STDOUT to be loaded into a variable, and the single quotes ensure that if there are any spaces in the directory name, it still gets loaded into a single variable. To use command substitution, enclose any command that generates output to standard output inside parentheses and precede the opening parenthesis with a dollar sign, $(command). Command substitution is useful when assigning a value to a variable. It is handy for using the output of one command as an argument to another command. [http://mywiki.wooledge.org/BashFAQ/082 Why is $(...) preferred over `...` (backticks)?] . A good use of this is in http://serverkb.co.uk/tools/slow.sh

* To quote double quotes (") do the following: echo -e "Testing \"quotes\" here" - this will show as Testing "quotes"
* Quotes prevent wildcard (*) expansion.

=== $? ===

This is the exit status/code of the last executed function/program/command.

=== [http://beyondgrep.com ack] ===

To look into.

=== [http://www.grymoire.com/Unix/Awk.html Awk] ===

To '''print out a list of just folders/file'''s you want, do;

<pre>ls -l filepath | awk '{print $9;}'</pre>

This won't work correctly if there is spaces in the filename. To resolve this, use [[Linux#Find | this]] command whilst in the directory itself.

To do multiple sections of a result, do:

awk '{print $1,$2,$4,$X;}'

If you want to '''get rid of/cut certain/specific lines/rows from STDOUT''' aka '''print a specific line''', use awk in this way:

<pre>awk 'NR==22'</pre>

This is for use ''without'' a file. This example will only display the 22nd row from your output.

Notes: Blank lines count as a row. To do multiple lines do awk 'NR==22,NR==25' . This will output line 22-25.

The command sed '22 ! d' would do the same as the awk 'NR==22' example.

To '''get rid of pipe symbols in a file''', do:

awk -F'|' '{print $1,$10}' FileWithPipes > FileWithoutPipes

Alternatively if you get a list, e.g of domains from MySQL with only one column selected, put them in a file and you can remove the pipes by doing:

<pre>cat domainlist | awk '{print $2}' > list</pre>

awk '{ printf "%-20s %-40s\n", $1, $2}' allows you to '''[http://stackoverflow.com/questions/6462894/how-can-i-format-the-output-of-a-bash-command-in-neat-columns print information in columns]'''

=== Cat ===

Parse JSON file:

<pre>cat file | python .mjson.tool</pre>

=== Cut ===

This tool can be used in an example where you get an output but want to strip it to exactly what you need e.g.

lookupipscript.sh <IPaddress>

Output below:

<pre>Plan : Bronze, Silver, Gold
Type : IPv4 or IPv6
URL : http
IP : 0.0.0.0(primary)</pre>

lookupipscript.sh <IPaddress> | sed 'row ! d' | awk '{print $column;}'

This would output 0.0.0.0(primary). To get just the IP address and not the "(primary)" section, do:

| cut -c 1-7

Cut counts the first number/letter as 1, not 0.

=== eval ===

Use this of you want run a variable after a pipe and to shorten down your scripts. e.g. in http://serverkb.co.uk/tools/getdns.sh

<pre>ns="ns.nameserver.co.uk"
d="domain.co.uk"
g="grep $d | grep -v 'DiG\|;'"

echo "dig @$ns $d A"
dig @$ns $d A | eval $g</pre>

It is a good replacement instead of $() or `` or running just a variable.

=== [http://unixhelp.ed.ac.uk/CGI/man-cgi?find Find] ===

==== [http://www.cyberciti.biz/faq/linux-unix-osx-bsd-find-command-exclude-directories Exclude directories] ====

==== [http://www.cyberciti.biz/tips/linux-findinglocating-files-with-find-command-part-1.html Guide Part 1] ====

[http://content.hccfl.edu/pollock/unix/findcmd.htm Find Help] (this includes [http://www.unix.com/tips-tutorials/20526-mtime-ctime-atime.html mtime] commands)

<pre>find . -maxdepth 1 -type f -printf "%f\n" | sed s/,$//</pre>

'''Finds all files that contain "some string"'''. This command is useful in a directory (e.g. mail), so you would do ls -lah | grep year-mm then:

<pre>find . -type f -exec grep -l "some string" {} \;</pre>

=== [http://www.thegeekstuff.com/2011/07/bash-for-loop-examples for loop examples] ===

=== Functions ===

A prime use of functions is in our script to replace the date.timezone settings in php.ini at http://serverkb.co.uk/tools/phptimezone.sh

<pre>#!/bin/bash
APACHEPHP="/etc/php5/apache2/php.ini"
CURRENT="\n\nThis is the current timezone configuration:"
DONE="If the settings were wrong, they are as below now:"
ETC="/etc/php.ini"

function UBDEB(){
echo -e "\nThe operating system is Debian/Ubuntu, so editing $APACHEPHP" $CURRENT
grep "date." $1 | head -7 | grep -v '; http\|Define' ; echo ""
sed -i -e 's/;date.timezone\ =/date.timezone\ =\ \"Europe\/London\"/g' $1
sed -i -e 's/;date.default_latitude\ =\ 31.7667/date.default_latitude\ =\ 51.500181/g' $1
sed -i -e 's/;date.default_longitude\ =\ 35.2333/date.default_longitude\ =\ 0.12619/g' $1
echo $DONE
grep "date." $1 | head -7 | grep -v '; http\|Define' ; echo ""
}

function RHEL(){
echo -e "\nThe operating system is likely CentOS, editing $ETC" "$CURRENT
grep "date." $1 | head -7 | grep -v '; http\|Define' ; echo ""
sed -i -e 's/;date.timezone\ =/date.timezone\ =\ \"Europe\/London\"/g' $1
sed -i -e 's/;date.default_latitude\ =\ 31.7667/date.default_latitude\ =\ 51.500181/g' $1
sed -i -e 's/;date.default_longitude\ =\ 35.2333/date.default_longitude\ =\ 0.12619/g' $1
echo $DONE
grep "date." $1 | head -7 | grep -v '; http\|Define' ; echo ""
}

if [[ `cat /etc/issue | sed '1 ! d' | awk '{print $1;}'` == "Debian" || `cat /etc/issue | sed '1 ! d' | awk '{print $1;}'` == "Ubuntu" ]];
then
UBDEB "$APACHEPHP"
else
RHEL "$ETC"
fi</pre>

Credit to Sam Teale for helping me with this.

=== Grep ===

If you are grepping a a .gz or .zip file you generally need to use zgrep.

==== Exclude multiple directories ====

<pre>grep 'string' -R . -il --exclude="/proc" --color
grep -iR "string" * | grep -v "/proc"</pre>

==== Look for IP address ====

do this:

grep -E -o '(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)'

courtesy of [http://stackoverflow.com/questions/427979/how-do-you-extract-ip-addresses-from-files-using-a-regex-in-a-linux-shell/428086#428086 SO]

==== Multiple terms ====

Exclude using -v

<pre>grep 'chroot\|default\|fs\|fs-passwd\|httpsdocs'</pre>

'''It is important to remember to not put a \| after the last text term.'''

This can be used with tail as well.

==== Remove pipe symbols from MySQL ====

mysql -pPASSWORD admin -e"select domain from domains;" grep -v "|" > FileWithoutPipes

==== Switches/flags ====

<pre>-A after
-B before</pre>

==== Wildcards for filepaths ====

From http://unix.stackexchange.com/questions/203195/wildcards-for-filepaths-arent-working-in-grep :

<pre>* in a regex is not like a filename glob. It means 0 or more of the previous character/pattern. So your examples would be looking for a A then 0 or more B then -DEF
. in regex means "any character" so you could fix your pattern by using
grep 'AB.*DEF'</pre>

=== Head ===

If for example you do /var/qmail/bin/qmail-qstat and it prints two separate lines, do this to get just the first line:

head -1

=== [http://www.dreamsyssoft.com/unix-shell-scripting/ifelse-tutorial.php If and Else] ===

[http://tldp.org/LDP/Bash-Beginners-Guide/html/sect_07_02.html Advanced if usage]

Use -f for files, -d for directories

<pre>if [ -f $VARIABLE ]
then
parameters (e.g. echo, mkdir, touch, rm)
fi</pre>

Combine if and $? to get to do something with the exit status of the last executed command.

<pre>if [ $? -eq 0 ]; then
commands
fi</pre>

If you want to prompt for both y and Y for yes input, use:

<pre>if [[ $variable1 = y || $variable2 = Y ]];</pre>

Another example of the above if x '''or''' y is [http://www.unix.com/302444803-post5.html here]. Use || to do if = x or y.

<pre>if [[ value = x || y ]</pre>

If you get the following error when executing a bash script outside of it's directory:

[[: not found

You need to either bash /file/path/to/script or alter the syntax to use:

<pre>-eq instead of =</pre>
or
<pre>(( command )) instead of [[ command ]]</pre>

=== If value equals multiple values ===

Using the syntax above:

<pre>echo -ne "Enter a server number (1, 2 or 3): "
read ServerNo

if [[ ( $ServerNo -eq 1 ) || ( $ServerNo -eq 2 ) || ( $ServerNo -eq 3 ) ]]; then
echo "$ServerNo is a valid server, continuing."
else
echo "$ServerNo is not a valid server, exiting."
fi</pre>

=== read ===

One of the simplest uses of this command is to do it like so:

<pre>echo -ne "Enter the filename you want to create: "
read createdfilename
touch $createdfilename</pre>

=== sed ===

If you want to '''get rid of/cut certain/specific lines/rows from STDOUT''' aka '''print a specific line''', use sed in this way:

sed '22 ! d'

This is for use ''without'' a file. This example will only display the 22nd row from your output.

Notes: Blank lines count as a row. The command awk 'NR==22' would do the same.

'''To print individual/separate lines, e.g. 1, 4 and 5:'''

sed -ne '1p;4p;5p'

'''To print between lines 22 to 39:'''

sed '22,39 ! d'

'''To put a variable inside sed, use quotes instead of apostrophes:'''

sed "22,$variable ! d"

'''To delete parenthesis/brackets, use this:'''

sed 's/['''()''']//g' 
sed 's/[''')''']//g' 
sed 's/['''(''']//g' 
sed 's/['''[]''']//g' 
sed 's/[''']''']//g' 
sed 's/['''[''']//g'

==== Replace text in a file ====

sed -i -e 's/TextToFindToReplace/TextToReplaceItWith/g' filename

To handle spaces, forward slashes and quotes " ", use back slashes like you do in filenames:

sed -i -e 's/'''File\"quotes\"WithA\ Space'''/''HereIs''\/''ABackslash''/g' filename

=== sleep and usleep ===

Use sleep if you want to "wait" X seconds. usleep is measured in microseconds and cannot do more than 1 second. 100000 (100,000 / 100k) = 0.1 seconds. 1,000,000 = 1 second.

=== Shells and subshells ===

If you want a script to make changes to your current shell, not the subshell a bash script works in, execute the script by doing the following (sometimes you may need to do ./ still):

<pre>. script</pre>

This information was provided by these sources: [http://stackoverflow.com/questions/874452/change-current-directory-from-a-script 1], [http://stackoverflow.com/questions/255414/why-doesnt-cd-work-in-a-bash-shell-script 2]

=== tee ===

Tee command is used to store and view (both at the same time) the output of any other command.

Tee command writes to the STDOUT, and to a file at a time.

By default the tee command overwrites the file. You can instruct tee command to append (like >> does) to the file using the option –a as shown below.

<pre>ls | tee –a outputfile</pre>

=== [http://mywiki.wooledge.org/BashFAQ/031 Use [[ instead of [] ===

=== Variables ===

If you store a variable with a command within it as follows:

<pre>variablename=`command`</pre>

you should instead store it like this:

<pre>variablename=$(command)</pre>

And then call it as follows:

<pre>${variablename}</pre>

=== Watch ===

Example/s:

To monitor a file's size:

<pre>watch -n 1 'ls -lh | grep filename'</pre>

=== xargs ===

This can be incredibly useful if you get "Argument list too long"

cd /to/directory , find . -type f | xargs rm -Rf

If you need to remove a list of files with spaces in them, do this:

<pre>ls -lah | grep "SpecificString" | awk '{print $9,$10,$11,$etc}' | xargs -I {} rm -v {}</pre>

Use ls -lh to not include hidden files/file starting with a full stop.

For simple removal of normal files do this in a screen session:

<pre>ls -lh | awk '{print $9}' | xargs -t rm</pre>

Otherwise try using find:

<pre>find . -exec grep PATTERN {} + | wc -l</pre>

Copying multiple files:

<pre>ls -lh | grep TEXT | awk '{print $9}' | xargs cp -t /target/path/</pre>

== Compare a remote file with a local file ==

ssh user@host cat /path/to/remotefile | diff /path/to/localfile -

Credit to User [http://www.commandlinefu.com/commands/by/root Root]

=== Compare files in a directory ===

diff -bur folder1/ folder2/

Warning: when doing diff on folders, if the timestamps are different it will think the files are different. If you actually compare the files, they will be the same.

== Console Clock in corner ==

while true; do echo -ne "\e[s\e[0;$((COLUMNS-27))H$(date)\e[u"; sleep 1; done &

'''Warning, this auto scrolls your SSH session'''. To kill it, do:

ps aux | grep bash | grep -v grep

Then kill the bash session at the time you ran it:

kill <processid>

Credit to User [http://www.commandlinefu.com/commands/by/SQUIIDUX Squiidux]

 -->

== Create symlink ==

https://www.cyberciti.biz/faq/creating-soft-link-or-symbolic-link/

How to chown a symlink: https://superuser.com/questions/68685/chown-is-not-changing-symbolic-link

Old method:

<pre>ln -s TARGET LINK_NAME</pre>

== Cronjob/Crontab ==

To check a cronjob has at least attempted to run/execute, check this at the time of execution:

<pre>tail -f /var/log/syslog | grep CRON</pre>

[http://www.openjs.com/scripts/jslibrary/demos/crontab.php Generator]

<pre>crontab -e
crontab -l

* * * * * command to be executed
- - - - -
| | | | |
| | | | +----- day of week (0 - 6) (Sunday = 0 or 7)
| | | +------- month (1 - 12)
| | +--------- day of month (1 - 31)
| +----------- hour (0 - 23)
+------------- min (0 - 59)
</pre>

Guides:

http://www.adminschoice.com/crontab-quick-reference

To do a job every X minutes, do */X * * * *

To do a job every minute in a specific hour, do * X * * *

To do a job every X hours, do * */X * * *

To do a job every day at X hour on the hour, do 0 9 * * * for 9am each day.

To do a job every week at 2am on Sunday, do 0 2 * * 0

To monitor active cron jobs, do tail -f /var/log/cron

=== /usr/local/bin/php: No such file or directory ===

Do whereis php

Generally it is actually in /usr/bin/php

== Cron Daemon email ==

If you get the below email:

<pre>cd / && run-parts --report /etc/cron.daily
/etc/cron.daily/sysklogd:
chown: cannot access `/var/log/mail.warn': No such file or directory
chown: cannot access `/var/log/syslog': No such file or directory
chown: cannot access `/var/log/mail.info': No such file or directory</pre>

Do the following:

<pre>cd /var/log
touch /var/log/mail.warn /var/log/syslog /var/log/mail.info
/etc/init.d/sysklogd restart</pre>

== Date ==

=== Spaces ===

To put spaces between variables (e.g +%H%M) use single quotes:

<pre>The time is `date '+%R:%S %Y %Z'` on the following Day/Month/Year `date '+%a %b %d'`</pre>

== Echo colours ==

[http://misc.flogisoft.com/bash/tip_colors_and_formatting Tips for colours and formatting]

Place 0; for the normal version (e.g. Black is 0;30) 
Place 1; before these to get the light colour version.

Here are the colour codes:

{| border="1" align="center" style="text-align:center;" class="collapsible collapsed wikitable"
|-
! colspan="3"|
|-
|'''Colour'''
|'''Foreground'''
|'''Background'''
|-
|Black
|30
|40
|-
|Dark Grey
|1;30
|1;40
|-
|Red
|31
|41
|-
|Light Red
|1;31
|1;41
|-
|Green
|32
|42
|-
|Light Green
|1;32
|1;42
|-
|Yellow
|1;33
|1;43
|-
|Brown
|0;33
|0;43
|-
|Blue
|34
|44
|-
|Light Blue
|1;34
|1;44
|-
|Magenta (Purple)
|35
|45
|-
|Light Purple
|1;35
|1;45
|-
|Cyan
|36
|46
|-
|Light Cyan
|1;36
|1;46
|-
|White
|37
|47
|-
|Light Gray
|0;37
|0;47
|-
|}

An example:

<pre>#!/bin/bash

wipe="\033[1m\033[0m"

black="40m"
darkggrey='\E[1;30m'
red='\E[31m'
lightred='\E[1;31m'
green='\E[32m'
lightgreen='\E[1;32m'
yellow='\E[1;33m'
brown='\E[0;33m'
blue='\E[34m'
lightblue='\E[1;34m'
purple='\E[35m'
lightpurple='\E[1;35m'
cyan='\E[36m'
lightcyan='\E[1;36m'
white='\E[37m'
lightgray='\E[0;37m'
green='\E[32m;'</pre>

<pre>echo -e "$green$black"
echo Hello World
echo -e "$wipe"</pre>

or

<pre>echo -e "Output a ${green}coloured${wipe} word."</pre>

<pre>./colourtest.sh

Hello World</pre>

The Hello World text appears green.

== Execute one off command whenever ==

echo "ls -l" | at midnight

This is an alternative to cron which allows a one-off task to be scheduled for a certain time.

Credit to User [http://www.commandlinefu.com/commands/by/root Root]

== File Locations (index priority) ==

/etc/apache2/mods-enabled/dir.conf (on Ubuntu) or /etc/httpd/conf/httpd.conf (on CentOS, ~line 402) and it should show something like:

<pre>DirectoryIndex index.html index.html.var index.shtml index.cfm index.php index.htm</pre>

This shows the default priority in which the index page is picked up and this can be set in the [[.htaccess]] file as well with:

<pre>DirectoryIndex index.html index.php</pre>

These are good places to check if you are using all of your [[Resource_Usage|disk space]].

cd /var/log 
cd /var/www/vhosts (website and statistics) 
cd /var/lib/mysql (database) or mysql/mysql 
cd /usr/bin/mysqldump (mysql dump) 
cd var/qmail (mail logs, queue and configuration) 
cd /var/lib/psa/dumps (physical Plesk backups) 
cd opt/psa/tmp/ (Plesk stores temporary files here for backups)

== File Permissions ==

[http://linuxcommand.org/lts0070.php One of the best permissions guide]

The values and their equivalent permissions. R is Read, W is Write and X is Execute. There are three sets on a file or folder (e.g. -rwx-w--w- , -rw-r--r-- , -rwxr-xrwx) so you need to put in a value of three (or four in rare occasions) for a file/folder e.g. 644.

<pre>0 --- 
1 --x
2 -w-
3 -wx
4 r--
5 r-x
6 rw-
7 rwx</pre>

'''The syntax for chmod is (for example) 755 fileorfolder. The -R option can also be used to set the permissions on anything below a folder.''' 
'''The syntax for chown is chown user:group fileorfolder . To apply the user:group to anything below a folder you need to use the -R option.'''

[http://permissions-calculator.org/ Permissions Calculator] 
[http://www.tuxfiles.org/linuxhelp/filepermissions.html Help Guide 1] 
[http://www.freeos.com/articles/3127?page=3 Help Guide 2] 
[http://en.wikipedia.org/wiki/Filesystem_permissions#Notation_of_traditional_Unix_permissions Unix Notation] 
[http://www.faqs.org/docs/linux_intro/sect_03_04.html File protection with chmod]

If you use PHP Support as '''Apache module, it will use the third value of''' -rw- r-- '''r-x''' to permissions. If it is using '''Fast CGI it will use the user:group''' for the first two values '''-rwx rw-''' --x

If you are using Plesk a good place to check if you are getting Forbidden errors on your website is /var/www/vhosts/yourdomain.com/httpdocs/statistics/logs/error_log . Access your site and tail -f that file. If you get .htaccess pcfg_openfile: unable to check htaccess file, ensure it is readable name your .htaccess file correctly, set your httpdocs to 757 and see [http://serverfault.com/questions/61726/permission-denied-home-htaccess-pcfg-openfile-unable-to-check-htaccess-file this link].

'''Special permissions'''

There is also a, g & s which are not widely used as it just needs additional representation at the special/setid permission to the group.

To set a file to -rws--x--x for example use

<pre>4 = setuid - s
2 = setgid - s
4 + 2 = S
1 = Sticky Bit
4 + 2 + 1 = T
2511 -r-x--s--x (e.g. /var/qmail/bin/qmail-remote or /var/qmail/bin/qmail-queue)
4655 -rwSr-xr-x
4711 -rws--x--x
4744 -rwsr--r--
4755 -rwsr-xr-x
6411 -r-S--s--x.
6511 -r-s--s--x
6644 -rwSr-Sr--
6666 -rwSrwSrw-
7000 ---S--S--T
7644 -rwSr-Sr-T
7711 -rws--s--t
7744 -rwsr-Sr-T
7755 -rwsr-sr-t</pre>

[http://serverfault.com/questions/111350/what-chmod-and-ownergroup-settings-are-best-for-a-web-application Owner and Group advice for websites]

== [http://adminlogs.info/2011/06/02/linux-find-command-tips Find command guide] ==

== [http://serverfault.com/questions/35076/need-to-fix-file-permissions-in-a-users-home-directory Fix file and folder permissions easily] ==

== FreeBSD ==

* mysqldump location: /mysql/bin/mysqldump
* Remove syntax:

- rm -r folderName
* Generic tunneling interface starts with gif

=== [http://forums.freebsd.org/showthread.php?t=5852 Check software versions] ===

=== fetch instead of wget ===

To download a file.

=== whereis instead of locate command ===

To find files/folders.

== Full Directory listing ==

<pre>apt-get install tree
yum install tree
tree > tree.txt</pre>

If you feel adventurous do cat tree.txt , it will take a while ;)

=== Find the deepest directory in your server/file structure ===

<pre>find . -type d -printf '%d:%p\n' | sort -n | tail -1</pre>

=== Find and remove specific file types from current directory ===

<pre>cd into the directory
find . -type f -name '*.filetype' -exec rm -v {} \;</pre>

=== Line count a file ===

wc -l /file/path

== Generate random number ==

Between 1 and 10:

seq 10| shuf | head -1

== GeoIP - Block countries accessing website ==

Ubuntu: apt-cache search geoip ; apt-get install geoip-database libgeoip-dev libgeoip1 python-geoip geoip-bin libapache2-mod-geoip tclgeoip 
CentOS: yum list |grep -i geo , yum install GeoIP.x86_64 
http://www.webhostingtalk.com/showthread.php?t=959646 
http://askmatt.co.uk/blog/2010/05/block-countries-using-apache-mod-geo-ip-list-of-countries-by-fraud-risk

== Gunzip and Zip ==

To gzip a file (.gz) up, do:

<pre>gzip file</pre>

The above won't work for folders.

Or if zip is installed:

<pre>zip -r filename.zip filename</pre>

To unzip a .gz file, do:

<pre>gunzip file</pre>

To extract a .tgz file, do:

<pre>tar zxvf fileNameHere.tgz</pre>

See http://serverkb.co.uk/wiki/Linux#tar_command for further details.

== [http://eng.eelcowesemann.nl/plesk/changing-the-servers-hostname-in-plesk Hostname guide] (rough) ==

If the server runs Plesk and Virtuozzo, the permanent one needs setting on the hardware or in Virtuozzo.

Run dig -x IP.IP.IP.IP from any Linux server and it will show you the PTR/hostname.

'''Note:''' Most servers by default come with a non resolving hostname of localhost, localhost.localdomain or something generic.

The hostname should never be left as the default value on a server sending mail, as it is one of three things mail recipient's mailservers see to determine if mail is spam or not. The other two are reverse DNS and the SMTP banner.

If Plesk throws an error when clicking Websites & Domains tab regarding hostname -f, see [[Plesk_Errors#Domains_area_is_blank | this resolution]].

== How to fix broken packages ==

Run the following commands below:

<pre>dpkg --configure -a
apt-get install -f
#or
apt-get -f install</pre>

If the problem still exists, then edit dpkg status file:

<pre>gksudo gedit /var/lib/dpkg/status</pre>

Find the package in question, and remove everything that has anything to do with it and save the file.

== How to install .deb files ==

<pre>dpkg -i filename.deb</pre>

== [[.htaccess]] ==

[http://en.wikipedia.org/wiki/Htaccess HyperText access]

== [http://stackoverflow.com/questions/653096/howto-free-inode-usage inode usage] ==

<pre>df --si
df -ih</pre>

A lot of the time the cause can be /tmp (/var/lib/php/session/ on Plesk) due to sessions. You may want to delete the files in there.

== Investigating high load ==

If you are getting a high load average in top, these are some of the steps you can take to investigate the issue.

Check which process has the most open of itself:

<pre>ps aux | awk '{print $11}' | sort | uniq -c | sort -nk1 | tail -n5</pre>

Stop that process, then run the above command a second time. Then start it again and run the command a third time.

=== Useful software ===

* top
* htop
* iotop

All these will do the job. Firstly check the CPU wait time, this is shown within top in Cpu(s): 8.0%us, 2.8%sy, 0.0%ni, 40.7%id, 48.3%wa

<pre>%wa in</pre>

If this is high, check the Status column (S column in top) to see if any are labelled D. The [http://stackoverflow.com/questions/666783/how-to-find-out-which-process-is-consuming-wait-cpu-i-e-i-o-blocked processes blocked on IO] are the ones marked as D.

=== On a Plesk server ===

Ensure sites are running PHP as Fast CGI Application instead of Apache module so you can see which USER the process is running as. Pressing the letter "c" on your keyboard will show the path and normally the website name.

<pre>wget http://serverkb.co.uk/tools/memcpu.sh ; chmod +x memcpu.sh ; ./memcpu.sh > usage.log &
tail -f usage.log</pre>

You can alter the PHP Handler on Plesk boxes in the psa database easily by doing:

<pre>mysql -uadmin -p`cat /etc/psa/.psa.shadow`;
use psa
select * from hosting\G
select dom_id,www_root,php_handler_type from hosting;
update hosting set php_handler_type="module" where dom_id=x;</pre>

If sites run PHP as an Apache module scripts will execute as the Apache user www-data, this can make it difficult to see which site they belong to. This also means scripts run with privileges of the Apache user so if an account is compromised an attacker can get access to all other accounts. Also running as Apache module can make the Apache process CPU report look artificially high. Running PHP as Fast-CGI executes scripts as an FTP user associated with each subscription allowing easier identification of problem scripts and limit the damage of rogue scripts.

CPU reports are not an easy way to determine server health. We'd recommend you look at changes and trends rather than the absolute numbers. Most importantly consider your real world performance.

== Linux Container ==

This install below is for an Ubuntu physical server, I may update this in the future for CentOS, Fedora and others.

https://help.ubuntu.com/12.04/serverguide/lxc.html

If you need to get file off the container, you can just scp it off. If the recipient server is slow, try moving the file to the host machine by doing:

scp -Psshport file root@hostIPaddress:~

=== Installation of LXC ===

<pre>apt-get install lxc
cat /etc/init/lxc-net.conf | grep USE_LXC_BRIDGE</pre>

If true set to false unless you want the containers to NAT to your servers real IP addresses, and to be accessible externally.

=== Pre-container creation steps ===

To reduce errors pre-container creation do the following:

<pre>dpkg-reconfigure locales
locale-gen en_GB
update-locale LANG=en_GB.UTF-8</pre>


=== Creating/deleting containers ===

[http://wiki.openvz.org/Download/template/precreated OpenVZ Template list]

Check the templates below and pick one:

<pre>cd /usr/lib/lxc/templates/ ; ls -lah</pre>

Create a container from one of the templates:

<pre>lxc-create -t ubuntu -n NameOfTheContainer</pre>

If you want to install the fedora package, do apt-get install yum

To delete it just do:

<pre>lxc-destroy -n NameOfTheContainer</pre>

=== Start/stop a container ===

<pre>lxc-start -n NameOfTheContainer -d</pre>

/etc/init.d/lxc stop

=== Access the container ===

The default user is 'ubuntu' with the password 'ubuntu', to enter a container, do:

<pre>lxc-console -n NameOfTheContainer
sudo -i</pre>

Exit using Ctrl + a, then press q

To re-enter the container, do lxc-console -n NameOfTheContainer and then press enter (you may have to a few times)

'''Access externally:'''

iptables -t nat -A PREROUTING -p tcp --dport 2222 -j DNAT --to 10.0.3.61:22

'''Make sure you remove this rule afterwards and DO NOT reboot your server.'''

=== Configuration settings ===

* By default you can ping a container from the host, and vice versa, and you can ping the outside world from the container.
* You can set the hostname just like a normal server, if you want to rename the container.

==== Default configuration of system files ====

<pre>cd /var/lib/lxc/nameofcontainer/rootfs/etc/sysconfig/network-scripts
vim ifcfg-eth0</pre>
<pre>DEVICE=eth0
BOOTPROTO=dhcp
ONBOOT=yes
HOSTNAME=phptester
NM_CONTROLLED=no
TYPE=Ethernet
MTU=</pre>

<pre>vim /var/lib/lxc/nameofcontainer/config</pre>
<pre>lxc.network.type=veth
lxc.network.link=lxcbr0
lxc.network.flags=up
lxc.network.hwaddr = MAC Address
lxc.utsname = MT</pre>

<pre>vim /etc/lxc/lxc.conf</pre>
<pre>lxc.network.type=veth
lxc.network.link=lxcbr0
lxc.network.flags=up</pre>

You can add the below to /etc/network/interfaces

<pre>auto br1
iface br1 inet dhcp
bridge_ports eth0</pre>

==== Fedora ====

The mirrors/repositories the container uses may be broken by default, don't try to install anything. You'll likely get:

''Error: Cannot retrieve repository metadata (repomd.xml) for repository: fedora. Please verify its path and try again''

And you likely won't be able to ping anything except the host machine and localhost/127.0.0.1

iptables -t nat -A POSTROUTING -s ContainerIP/24 -j SNAT --to-source PhysicalHostIP 
iptables -t nat -A PREROUTING -m tcp -p tcp --dport 10022 -j DNAT -i eth0 --to-destination ContainerIP:80 
iptables -t nat -A PREROUTING -m tcp -p tcp --dport 10443 -j DNAT -i eth0 --to-destination ContainerIP:443

[https://www.berrange.com/posts/2011/09/27/getting-started-with-lxc-using-libvirt libvirt]

<pre>vi /etc/yum.repos.d/fedora.repo
vi /etc/yum.repos.d/fedora-updates.repo</pre>

Uncomment (#) the lines starting with "baseurl"

yum update

==== OpenSUSE ====

[http://en.wikipedia.org/wiki/OpenSUSE#Version_history Version history]

http://www.lacerta.be/d7/content/opensuse-lxc-container-inside-ubuntu

=== List containers ===

lxc-list

=== Set passwords ===

Log in as the root user of the container:

'''Fedora''' container:

<pre>Username: root
Password: root</pre>

Set the root password to something different:

<pre>passwd</pre>

You will need to do yum install vim when inside the server.

'''Ubuntu''' container:

<pre>sudo -i
Username: ubuntu
Password: ubuntu</pre>

Set the user's password:

<pre>passwd ubuntu</pre>

Set the root user's password:

passwd

=== SSH in externally ===

'''To route from externally through the host to the container, just do the below iptables rule''':

<pre>iptables -t nat -A PREROUTING -p tcp --dport 1337 -j DNAT --to 10.0.4.60:22
iptables-save</pre>

In the above case we are saying:

- You want to SSH in on port 1337 
- The container's eth0 IP address is 10.0.4.60 
- Then below we are saying the physical machine has an IP address of 110.111.112.113

Then externally from the server do:

<pre>ssh root@110.111.112.113 -p2222</pre>

And bingo! You should be in the container.

<pre>passwd</pre>


== [http://wiki.debian.org/LSBInitScripts LSB Init Scripts] ==

== ls list only directories or files ==

Directories:

<pre>ls -lad */</pre>

Files:

<pre>ls -la | grep -v ^d</pre>

== Kill tty session ==

<pre>w
ps aux | grep bash | grep -v grep
ps aux | grep tty | grep -v grep
kill -HUP <processid></pre>

[http://www.cyberciti.biz/faq/howto-kill-unix-linux-user-session Further info]

== Maldet ==

[http://www.rfxn.com/projects/linux-malware-detect Documentation] 
[http://www.rfxn.com/downloads/maldetect-current.tar.gz Maldet .tar.gz] 
[http://blog.hostonnet.com/how-to-install-and-configure-maldet-linux-malware-detect-lmd Install and Configure]

<pre>cd /root ; wget http://serverkb.co.uk/tools/maldet.sh ; chmod +x maldet.sh ; ./maldet.sh</pre>

Always run your scans from chroot environment (if it has one/is possible) and in Screen (screen -S NameIt), and detach by doing CTRL + A, then press D

Scan reports are normally stored in /usr/local/maldetect/sess/ as session. files.

maldet -a -e -l filepath

== Manually alter time/date ==

'''Ubuntu'''

<pre>date
date mmddtimeyear #as seen below</pre>

'''Cent OS'''

<pre>cd /etc/
ls -lah
rm localtime
ln -s /usr/share/zoneinfo/Europe/London /etc/localtime
date mmddtimeyear
| | | | ---> 2012
| | | 24hr --> XX:XX without :
| | dd -------> day
| mm ---------> month

/etc/init.d/ntpd restart or start
date</pre>

== Move files into your home directory not owned by your own user ==

Copy to /var/tmp or /tmp (for small files) and do:

<pre>chmod ugo+rw <filename></pre>

== PID ==

Under construction.

Process ID.

To determine the usage of a specific process, do top -p PID

The maximum number of pids can be obtained from /proc/sys/kernel/pid_max

== .profile ==

Put this in .profile file for on user startup:

<pre>echo "" ; df -h | sed -ne '1p;5p' ; echo "rootfs"
echo "" ; free -m
echo "" ; w | head -1 | sed 's/^ *//g'
echo "" ; w | tail -10 | grep -v average ; echo ""</pre>

== Proxmox ==

To access via the web go to https://IPaddress:8006

Rough notes:

apt-get install sudo

Proxmox

/var/lib/vz

dump is for backups 
images is for OS images 
private is for OpenVZ container file systems 
template/cache is for OpenVZ templates

http://openvz.org/Download/template/precreated

Create VM creates KVM 
Create CT creates OpenVZ container 

vzctl enter id 
vzctl start/stop id 

iptables -t nat -A POSTROUTING -o vmbr1 -j MASQUERADE 
restart networking on host and CT

=== cman_tool: Cannot open connection to cman ===

<pre>pvecm status
pvecm nodes
cman_tool: Cannot open connection to cman, is it running ?</pre>

<pre>service pve-cluster restart
pvecm delnode NodeName</pre>

=== Force remove an OpenVZ container ===

<pre>vzctl stop 100 ; vzctl destroy ContainerID
cd /var/lib/vz/private
rm ContainerIDfolder -R
cd /var/lib/vz/root
rm ContainerIDfolder -R
cd /etc/pve/nodes/ContainerName/openvz
mv ContainerID.conf ContainerID.bak</pre>

Make sure it does not exist in cat /etc/pve/.members

=== Remount a logical partition/volume ===

lvdisplay

/dev/mapper/pve-data /var/lib/vz (this will be different in your file system)

=== Unable to get local IP address ===

<pre>/etc/init.d/pve-cluster restart
service pve-cluster start
Starting pve cluster filesystem : pve-cluster[main] crit: Unable to get local IP address
(warning).</pre>

Make sure in /etc/hosts your domain name resolves to the server and you also have it without the .co.uk/.com etc in the file as so:

<pre>ServerIPaddress domain.co.uk domain pvelocalhost
127.0.0.1 localhost localhost.localdomain</pre>

Then do:

<pre>/etc/init.d/hostname.sh stop
/etc/init.d/hostname.sh start
service pve-cluster start</pre>

=== Transport endpoint is not connected ===

<pre>df -h
df: `/etc/pve': Transport endpoint is not connected</pre>

<pre>ls -lah /etc/pve
ls: cannot access pve: Transport endpoint is not connected
d????????? ? ? ? ? ? pve</pre>

Do this:

<pre>umount /etc/pve
pvecm status</pre>

You will get:

unable to get IP for node 'hostname' - node offline?

The fix is the same as [[Linux#Unable_to_get_local_IP_address | this]] one, ensure you have the domain without the web extension in /etc/hosts resolving to the servers IP address. Then do:

service pve-cluster start

== Recover deleted files ==

You need to install this software before you delete any files:

<pre>apt-get install foremost</pre>

Then see this documentation:

https://help.ubuntu.com/community/DataRecovery 
http://ddailygirl.wordpress.com/2010/08/17/recovering-files-after-rm-in-linux 
http://www.howtoforge.com/recover-deleted-files-with-foremost 
http://www.webupd8.org/2009/03/recover-deleted-files-in-ubuntu-debian.html

== Remove file starting with dash ==

<pre>rm -- -filename</pre>

Remove folder starting with dash

<pre>rm -rf -- -folder/</pre>

== Remove/rename file called tilde ==

<pre>mv '~' newfilename
rm '~'</pre>

== Restart service or service ==

Useful for differently named ones, e.g.

[ -f /etc/init.d/mysqld ] && service mysqld restart ; [ -f /etc/init.d/mysql ] && service mysql restart

[ -f /etc/init.d/httpd ] && service httpd restart ; [ -f /etc/init.d/apache2 ] && service apache2 restart

== Roughly list file count ==

This includes nested directories:

<pre>find /full/file/path -type f | wc -l</pre>

== SCP Command - Secure Copy ==

To secure copy a file from one Linux server to another, use the following syntax form:

<pre>scp -P PORT file user@IPAddress:/filepath</pre>

For example:

<pre>scp -P 22 index.html root@127.0.0.1:/</pre>

To move a folder, put -r in between the port and the file(s)/folder(s) like so:

<pre>scp -P 22 -r testdirectory/ root@127.0.0.1:/</pre>

If you receive the following error while trying to SCP a file from one server to the other:

<pre>stdin: is not a tty</pre>

You can solve the issue quickly by doing the following on the destination server:

<pre>vi ~/.bashrc

if [ $(expr index "$-" i) -eq 0 ]; then
return
fi</pre>

== Screen ==

Re-join screen session

<pre>screen -r</pre>

or

<pre>screen -D -r '1234.somescreensession'</pre>

A better alternate is [[Linux#tmux | tmux]].

[http://www.ubuntugeek.com/screen-manages-multiple-sessions-on-one-terminal.html#more-1415 Manage Multiple sessions in one Terminal] 
[http://www.samsarin.com/blog/2007/03/11/gnu-screen-working-with-the-scrollback-buffer Scrollback] (vim /home/.screenrc + defscrollback 1000) 
[http://polishlinux.org/howtos/screen-tips-tricks Tips and Tricks]

== Setting the time ==

http://geoffhankerson.com/node/112 
http://codeghar.wordpress.com/2007/12/06/manage-time-in-ubuntu-through-command-line/

== Standard redirection ==

http://www.xaprb.com/blog/2006/06/06/what-does-devnull-21-mean/

STDIN, STDOUT and STDERR.

0, 1 and 2

1>/dev/null 
2>/dev/null

== sudo ==

If you exit out of root access and want to run the last command you entered without authentication, do:

<pre>sudo !!</pre>

== System Logs and Shutdown troubleshooting ==

If you are having an issue, a reboot should not be performed if the server can be accessed in any way (e.g. locally in the data centre, only if it is a Dedicated server). This is because after a reboot there is little you can find out from the logs as the important logs get cleared on restart.

<pre>last reboot
last</pre>

Do this to check which files exist:

ls -lh /var/log/syslog ; ls -lh /var/log/kern.log ; ls -lh /var/log/dmesg ; ls -lh /var/log/messages

Then do one or more of these depending on which exist:

grep -i error /var/log/syslog ; grep -i panic /var/log/syslog ; grep -i warning /var/log/syslog 
grep -i error /var/log/dmesg ; grep -i panic /var/log/dmesg ; grep -i warning /var/log/dmesg 
grep -i error /var/log/kern.log ; grep -i panic /var/log/kern.log ; grep -i warning /var/log/kern.log 
grep -i error /var/log/messages ; grep -i panic /var/log/messages ; grep -i warning /var/log/messages

errpt may show an error report on some Unix OS'.

To find .log files, run [[Linux#updatedb_.28locate_command.29 | updatedb]] and then locate *.log

To restart and [http://go2linux.garron.me/reboot-check-disks-for-errors-avoid-force-fsck on boot do a disk check] do (or -rF):

<pre>shutdown -Fr now</pre>

== [http://www.pendrivelinux.com/how-to-open-a-tar-file-in-unix-or-linux tar command] ==

To archive and compress a folder/files do:

<pre>tar -czvf files.tgz files/
tar -czvf folder.tar.gz folder/
tar cvf mubackup.tar mu/ ; gzip -9 mubackup.tar

#.tgz is same as .tar.gz</pre>

c creates the archive (tar), z compresses it into the gzip, v is verbose, f is the file/folder

To extract do:

<pre>#for tar
tar xvf file.tar

#for .tgz or tar.gz
tar zxvf file.tar.gz</pre>

[http://www.fluidthoughts.com/howto/tar-gzip/ Guide 1] 
[http://www.thegeekstuff.com/2010/04/unix-tar-command-examples/ Guide 2] 
[http://superuser.com/questions/305128/how-to-specify-level-of-compression-when-using-tar-zcvf 3] and [http://superuser.com/questions/156207/untar-ungz-gz-tar-how-do-you-remember-all-the-useful-options 4]

For bz2 files, use:

<pre>tar -xvjpf file</pre>

== top ==

The TIME column in top is displayed in minutes:seconds.hundredths

== tmux ==

C-c is CTRL+C 
C-m is ENTER

=== New session ===

Latest:

<pre>tmux new -s session_name</pre>

Old:

<pre>tmux new-session -n NameTheSession</pre>

=== Detach from a session ===

<pre>CTRL +B then D</pre>

=== Kill session ===

<pre>tmux kill-session -t myname</pre>

If this fails and it says:

"''session not found''"

Do the following:

<pre>tmux ls
tmux kill-session -t X</pre>

- where X is the number of the session on the left.

=== List sessions available ===

<pre>tmux ls</pre>

=== Re-attach to session ===

<pre>tmux attach
tmux attach -t ID or NameTheSession</pre>

=== Remotely execute a command ===

<pre>tmux send-keys -t ID "command" ENTER</pre>

== User ID 99 ==

This is most commonly the user nobody. This can be caused by PHP or done on purpose. cat /etc/passwd | grep 99 ; vim /etc/passwd

== User is not in the sudoers file ==

If you try to sudo into a server or run sudo and get the following message:

"''is not in the sudoers file. This incident will be reported.''"

Do the following command as root and add the username into the file in the same format as the root user:

visudo

== Use unusual characters in filenames ==

If you want to specify a space, lets say the file = /usr/local/etc/'''testingdatabase.sql'''

You need to name the file/folder as follows:

<pre>mv /usr/local/etc/testingdatabase.sql /usr/local/etc/testing\ database.sql</pre>

This will make the file be '''testing database.sql''' , on command line this will appear as '''testing\ database.sql''' .

A backslash symbol \ needs to be used before an apostrophe ' , bracket (), exclamation/bang ! symbol or question marks ?:

<pre>01\ -\ It\'s\ You.txt
#How it appears: 01 - It's You.txt

02\ -\ Boom\!.m3u
#How it appears: 02 - Boom!.m3u

03\ -\ Why\ Wont\ You\ Work\?.sh
#How it appears: 03 - Why Wont You Work?.sh

04\ -\ Musical\ Playlist\ For\ $VPS$\ Server.m3u
#How it appears: 04 - Musical Playlist For (VPS) Server.m3u</pre>

== updatedb (locate command) ==

This command is used when you cannot '''locate''' a file and you get "''locate: warning: database /var/lib/slocate/slocate.db' is more than 8 days old''". It is advised to run updatedb '''at least once a month'''. However if you get the following error when using it:

<pre>updatedb: fatal error: load_file: Could not open file: /etc/updatedb.conf: No such file or directory</pre>

You need to create or edit this file

<pre>vim /etc/updatedb.conf</pre>

and put the following inside of it:

PRUNE_BIND_MOUNTS="yes"PRUNEPATHS="/tmp /var/spool /media"PRUNEFS="NFS nfs nfs4 rpc_pipefs afs binfmt_misc proc smbfs autofs iso9660 ncpfs coda devpts ftpfs devfs mfs shfs sysfs cifs lustre_lite tmpfs usbfs udf"

Alternatively run the below script after reading this file http://serverkb.co.uk/tools/README.txt:

http://serverkb.co.uk/tools/updatedbscript.sh

To vim a file you locate, see [http://stackoverflow.com/questions/8228831/why-does-locate-filename-xargs-vim-cause-strange-terminal-behaviour this]. vim $(command)

=== Cannot find an existing file ===

Ensure that the directory path of the file that '''does''' exist is not in the following section in /etc/updatedb.conf:

<pre>PRUNEPATHS="/tmp /var/spool /media"</pre>


== vim ==

To make a copy the line below where you cursor is, hold CTRL + e. Then put a hash (comment) in front of this line. This is useful for backing up an old value before changing it.

=== Create backup of file whilst in vim ===

<pre>vim file
:!cp % %-</pre>

Press enter and continue to edit

Credit to User [http://www.commandlinefu.com/commands/by/mpb MPB]

=== Enter Insert mode ===

Press the letter i (I)

=== Enter Replace mode ===

Press the letter r (R)

=== E21: Cannot make changes, 'Modifiable' is off ===

<pre>:set modifiable</pre>

=== Search in file for multiple terms ===

Go to search mode i.e. type '/' and then type \v followed by the words you want to search separated by '|' (pipe).

Example:

<pre>/\vword1|word2|word3</pre>

Go to search mode and type the words you want to search separated by '\|'.

Example:

<pre>/word1\|word2\|word3</pre>

The first way puts you in the regular expression mode so that you do not need to put any extra back slashes before every pipe or other delimiters used for searching.

=== See changes made before exiting ===

<pre>:w !diff % -</pre>

=== Editing a jar/zip file ===

(zip#Write) sorry, your system doesn't appear to have the zip pgm

1) Check zip is installed

2)

<pre>:set modifiable
:set write</pre>

3)

E382: Cannot write, 'buftype' option is set

Check if the file has -e on it using:

<pre>lsattr filename</pre>

If so, you likely cannot edit it.

4)

Alternatively, download the file (e.g. a jar) and use an Archive tool like 7-zip to edit it.

== [http://www.cymru1.net/linux-vps/vps-hints-and-tips.php VPS Hints and Tips] ==

To check for the filepath of a command run top and then press c.

If it is a container on a node, there are generally no datacentre / rack level restrictions as the container is virtualised on a node. The only restrictions are what is put in place via the container itself effectively.

To list all open Internet, x.25 (HP-UX), and UNIX domain files, use:

lsof -i -U

== WHOIS script ==

[http://www.ivarch.com/programs/pv.shtml Pipe Viewer], [http://linux.die.net/man/1/pv PV info page]

<pre>apt-get install pv ; cd /var/www/vhosts ; ls -l | awk ' {print $9}' > domainlist ; wget serverkb.co.uk/tools/findregistrar.sh ; chmod +x findregistrar.sh</pre>

For CentOS use yum -y install jwhois.x86_64

Edit the file and replace domain registrar with the one you want to find. Then do:

<pre>./findregistrar.sh</pre>

== write error ==

If you get the following error when doing write user TTYsession or write user Session:

write: write: you have write permission turned off.

Do this to fix the problem:

mesg y

== [http://linuxcommand.org/writing_shell_scripts.php Writing Shell Scripts] ==