Here are some of most essential Linux commands which I often use and might be a one page reference for you as well.

Search/Find

find . -exec grep “searchterm” ‘{}’ \; -print

Above command will find a searchterm in all files in the present directory and will print it on screen.

If you want to search for a term in specific folders then use following command.

find /home/*/public_html/ -exec grep “searchterm” ‘{}’ \; –print

Above command comes very handy when you want to search for any term in all of your websites hosted on a single host. It also helps you to find any malware of hack scripts.

You can capture the result in a file using this command instead of displaying on the screen

find /home/*/public_html/ -exec grep “searchterm” ‘{}’ \; –print > result.txt

Find .htaccess files in /home
find /home/*/ -type f -name .htaccess

Searches for .htaccess files in /home/user top level folders and doesn’t search in the subfolders.
find /home -maxdepth 2 -type f -name .htaccess

find /home/*/public_html/wp-content/ -maxdepth 1 -type f -name .htaccess

IP Address related/Netowrking

/etc/ips –  Contains the IP address and Netmasks.

If you want to change any entries in this file then you will have to run following commands

service ipaliases restart

/etc/init.d/ipaliases reload

/scripts/rebuildippool

Disk Space

df -k

This shows the disk space in kilo blocks. The following command shows the disk paces used and available.

df -hP

df -h |grep “[0-9]G”  this is very handy command, it lists all the files in which has G size.

du -h |grep “[0-9]G”  this is very handy command, it lists all the files in which has G size.

du -h |grep “^[0-9,]\+G” shows the file sizes in G

du -sh /home/*  - this will show the sizes for the folders in /home folder.

cd /

du -sch *

This shows the directory sizes in M/G

du -h shows files in K/M/G sizes.

If / is full then remove the unused log files from /var/log/*

Hard Drive

S.M.A.R.T tool

S.M.A.R.T tool is a an excellent tool to obtain hard drive details and also to check hard drive’s overall health. If you have installed and configured this utility then it will also send you the alert if hard drive fails.

smartctl -H /dev/sda

Checks the overall health of hard drive. It will also report any hard disk failure.

smartctl -i /dev/sda

With this command you can obtain all the information on a hard drive.

Short test for hard drive
smartctl –test=short /dev/sda

Long test for hard drive
smartctl –test=long /dev/sda

Full test for hard drive
smartctl -a /dev/sda

FTP

To restart pure-FTP

service pure-ftpd start

Check FTP service status

service pure-ftpd status

Apache

Restart Apache in centOS

/sbin/service httpd restart

Start Apache in centOS

/sbin/service httpd start

Stop Apache in centOS

/sbin/service httpd stop

PHP

How to find the default php.ini file location.

php -r “phpinfo();” | grep Configuration

Configuration File (php.ini) Path => /usr/local/lib
Loaded Configuration File => /usr/local/lib/php.ini

Flush a Slow Query Log in MySQL

cd /var/lib/mysql

mv mysqladmin flush-logs mysqladmin flush-logs.old

mysqladmin flush-logs

Cleaning large eximstats mysql database

If eximstats directory (/var/lib/mysql/eximstats) contains large files and it is eating up space then celan it up by following commands

#mysql
#use eximstats
>delete from sends;
>delete from smtp;
>delete from failures;
>delete from defers;

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