Common SSH Commands or Linux Shell Commands

Commands	Description
cat	Print file contents to the screen
cat filename.txt	Cat the contents of filename.txt to your screen
cd -	Change directory
cd ..	Go up a directory
cd /usr/local/apache	Go to /usr/local/apache/ directory
cd ~	Go to your home directory
cp -a /home/burst/new_design/* /home/burst/public_html/	Copies all files, retaining permissions form one directory to another.
cp	Copy a file
cp filename filename.backup	Copies filename to filename.backup
du	Shows disk usage.
du -sh	Shows a summary in human-readable form of total disk space used in the current directory, including subdirectories.
du -sh *	Same thing goes with (du -sh), but for each file and directory. This is helpful when finding large files taking up space.
file	Attempts to guess what type of file a file is by looking at its content.
file*	Prints out a list of all files/directories in a directory
find * -type d|xargs -i cp --verbose php.ini {}	Copies your php.ini file into all directories recursively.
grep	Looks for patterns in files
grep -v root /etc/passwd	Shows all lines that do not match the root
grep root /etc/passwd	Shows all matches of root in /etc/passwd
kill	Terminate a system process
kill : 9 PID EG	kill -9 431
kill PID EG	kill 10550 Use top or ps ux to get system PIDs (Process IDs)
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
ln	Create's "links" between files and directories
ln -s /home/username/tmp/webalizer webstats	Now you can display http://www.yourdomain.com/webstats to show your Webalizer stats online. You can delete the symlink (webstats), and it will not delete the original stats on the server.
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.
more	Like a cat, but opens the file one screen at a time rather than all at once
more /etc/userdomains	Browse through the userdomains file. hit Space to go to the next page, q to quit
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.
pico	Friendly, easy to use file editor
pico /home/burst/public_html/index.html	Edit the index page for the user's website.
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. A process ID is a unique number that identifies a process, with that, you can kill or terminate a running program on your server (see kill command).
ps aux	Shows all system processes
ps aux --forest	Shows all system processes like the above but organizes in a beneficial hierarchy
ps U username	Shows processes for a certain user
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.

tail	Like a cat, but only reads the end of the file
tail -f /var/log/messages	Watch the file continuously while it's being updated
tail /var/log/messages	See the last 20 (by default) lines of /var/log/messages
tail -200 /var/log/messages	Print the last 200 lines of the file to the screen
top	Shows live system processes in a nice table, memory information, uptime, and other useful info. This is excellent for managing your system processes, resources and ensure everything is working fine, and your server isn't bogged down. top Shift + M to sort by memory usage Shift + P to sort by CPU usage
touch	Create an empty file
touch /home/burst/public_html/404.html	Create an empty file called 404.html in the directory /home/burst/public_html/
vi	Another editor, tons of features
vi /home/burst/public_html/index.html	Edit the index page for the user's website.
w	Shows who is currently logged in and where they are logged in from.
wc -l filename.txt	It tells how many lines are in filename.txt
wc	word count.

EG:

PID	TTY	TIME	COMMAND
10550	pts/3	0:01	/bin/csh
10574	pts/4	0:02	/bin/csh
10590	pts/4	0:09	APP

Each line represents one process, with a process being loosely defined as a running instance of a program. The column-headed PID (process ID) shows the assigned process numbers of the processes. The heading COMMAND shows the location of the executed process.
 

Putting commands together

Often you will find that you need to use different commands on the same line.
Here are some examples.

• The | character is called a pipe, and it takes a date from one program and pipes it to another.
• > means create a new file, overwriting any content already there.
• >> means to append data to a file, creating a new one if it does not already exist.
• < send input from a file back into a command.
  • grep User /usr/local/apache/conf/httpd.conf | more - This will dump all lines that match User from the httpd.conf, then print the results to your screen one page at a time.
  • last -a > /root/lastlogins.tmp - This will print all the current login history to a file called lastlogins.tmp in /root/
  • 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
  • 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 occurrences of domain.com (the period represents 'anything,' comment it out with a so it will be interpreted literally), then send it to your screen page by page.
  • tar -zxvf file.tar.gz  - UnTAR file
  • which [perl]  -  Finding path to [perl]

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