Common SSH Commands or Linux Shell Commands

ls : list files/directories in a directory, comparable to dir in windows/dos.
ls -al : shows all files (including ones that start with a period), directories, and details attributes for each file.

cd : change directory
cd /usr/local/apache : go to /usr/local/apache/ directory
cd ~ : go to your home directory
cd – : go to the last directory you were in
cd .. : go up a directory

cat : print file contents to the screen
cat filename.txt : cat the contents of filename.txt to your screen

tail : like cat, but only reads the end of the file
tail /var/log/messages : see the last 20 (by default) lines of /var/log/messages
tail -f /var/log/messages : watch the file continuously, while it’s being updated
tail -200 /var/log/messages : print the last 200 lines of the file to the screen

pico : friendly, easy to use file editor
pico /home/underhost.com/public_html/index.html : edit the index page for the user’s website.

vi : another editor, tons of features
vi /home/underhost.com/public_html/index.html : edit the index page for the user’s website.

grep : looks for patterns in files
grep root /etc/passwd : shows all matches of root in /etc/passwd
grep -v root /etc/passwd : shows all lines that do not match root

touch : create an empty file
touch /home/underhost.com/public_html/404.html : create an empty file called 404.html in the directory /home/underhost.com/public_html/

ln : create’s “links” between files and directories

rm : delete a file
rm filename.txt : deletes filename.txt, will more than likely ask if you really want to delete it
rm -f filename.txt : deletes filename.txt, will not ask for confirmation before deleting.
rm -rf tmp/ : recursively deletes the directory tmp, and all files in it, including subdirectories.

Be extremely careful with using rm. If used improperly you can end up deleting important content that can never be recovered without a restore.

last : shows who logged in and when
last -20 : shows only the last 20 logins
last -20 -a : shows last 20 logins, with the hostname in the last field

w : shows who is currently logged in and where they are logged in from.

netstat : shows all current network connections.
netstat -an : shows all connections to the server, the source and destination ips and ports.
netstat -rn : shows routing table for all ips bound to the server.

top : shows live system processes in a nice table, memory information, uptime and other useful info.
Shift + M to sort by memory usage
Shift + P to sort by CPU usage

ps : ps is short for process status, which is similar to the top command. It’s used to show currently running processes and their PID.
ps U username : shows processes for a certain user
ps aux : shows all system processes
ps aux –forest : shows all system processes like the above but organizes in a hierarchy that’s very useful!

file : attempts to guess what type of file a file is by looking at it’s content.
file * : prints out a list of all files/directories in a directory

du : shows disk usage.
du -sh : shows a summary, in human-readble form, of total disk space used in the current directory, including subdirectories.
du -sh * : same thing, but for each file and directory. helpful when finding large files taking up space.

wc : word count
wc -l filename.txt : tells how many lines are in filename.txt

cp : copy a file
cp filename filename.backup : copies filename to filename.backup
cp -a /home/burst/new_design/* /home/underhost.com/public_html/ : copies all files, retaining permissions form one directory to another.
find * -type d|xargs -i cp –verbose php.ini {} : copies your php.ini file into all directories recursively.

kill : terminate a system process
kill -9 PID EG : kill -9 431
kill PID EG : kill 10550

tail -10000 /var/log/exim_mainlog | grep domain.com | more
This will grab the last 10,000 lines from /var/log/exim_mainlog, find all occurances of domain.com

netstat -an | grep :80 | wc -l
Show how many active connections there are to apache (httpd runs on port 80)

mysqladmin processlist | wc -l
Show how many current open connections there are to mysql

mysqldump -u username -p dbname > file.sql
MySQL Dump

mysql -u username -p database_name <file.sql
Importing MySQL database

tar -zxvf file.tar.gz
UnTAR file

which [perl]
Finding path to [perl]