Getting Started with Linux Commands

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Last modified: July 13, 2022

Overview

While cPanel & WHM automates many server administration tasks, familiarity with the Linux® command line interface (CLI) can prove useful for both WHM and cPanel users. This documentation gives a brief overview of some basic Linux commands that you may wish to use as you manage your website or server.

Note:

For steps to access the command line, read our How to Access the Command Line documentation.

Common Linux commands

Note:

To execute a command, enter the command with any required options and press Enter.
In the following examples, replace FILENAME with the relative path to the file.

The following lists some basic Linux commands and their functions:

Command	Description	Example
`cat FILENAME`	Print the contents of the specified file to the CLI.	`cat filename.txt`
`cat /dev/vcs1`	View the data that currently displays on your server’s console screen.	`cat /dev/vcs1`
`cd LOCATION`	Navigate between directories. Replace `LOCATION` with the path to the directory that you wish to navigate to.	`cd /usr/local/apache/`
`chmod permissions FILENAME`	Change a file’s octal permissions. For more information, read Wikipedia’s `chmod` command article.	`chmod 755 myfile.txt`
`chown USER:GROUP FILENAME`	Change a file’s user and group ownership. Replace `USER` with the user to whom you wish to grant ownership of the file, `GROUP` with the group name, and `FILENAME` with the relative path to the file.	`chown user:usersgroup usersfile.txt`
`cp FILE1 FILE2`	Copy a file (`FILE1`) into a new file (`FILE2`).	`cp original.txt /copies/duplicate.txt`
`du`	Show the system’s current disk usage for each directory and subdirectory.	`du`
`file FILENAME`	Guess a file’s type, based on the file’s contents.	`file filename`
`grep string FILENAME`	Search for a string in a specified file and print each line that contains a match to the CLI. Replace `string` with a single word, or multiple words within single quotes (`''`).	`grep 'thisis anexample' filename.txt`
`last`	List which users recently logged in and the timestamp for each login.	`last`
`ln -s file1 file2`	Create a symbolic link between the two specified files. Replace `file1` with the relative path to the existing file, and `file2` with the relative path to the new symbolic link file.	`ln -s /pointtome/file1.txt symlink-file2.txt`
`ls`	List files and directories that exist within your current directory. This command resembles the `dir` command in Windows®.	`ls`
`ls -al`	View dotfiles (filenames that begin with a period) and additional file and directory details.	`ls -al`
`more FILENAME`	Print the contents of a file to the CLI, one screen at a time.	`more filename.txt`
`netstat`	List all of the server’s current network connections.	`netstat`
`pico FILENAME`	Open the specified file in the pico text editor).	`pico filename.txt`
`ps`	Return information about the server’s current processes. Note: To view all of the running processes add the `-auxww` or `-cef` option to this command.	`ps`
`rm FILENAME`	Delete the specified file. After you run this command, the system prompts you to confirm the file’s deletion.	`rm trash.txt`
`tail -## FILENAME`	Print the last lines of a file to the CLI, where `##` represents the number of lines to print.	`tail -20 filename.txt`
`touch FILENAME`	Create an empty file in the specified location.	`touch example.txt`
`vi FILENAME`	Open the specified file in the vi text editor.	`vi filename.txt`
`w`	List currently logged-in users and the location from which they logged in.	`w`
`wc FILENAME`	Display the word count for a specific file.	`wc example.txt`
`whereis NAME`	Query applications that match the `NAME` value. You can find the most common applications in the following locations: `/usr/sbin/sendmail` `/usr/bin/perl` `/bin/mail` `/usr/bin/php`	`whereis perl`

Run multiple commands on the same line

Various command-line tasks may require that you use different commands on the same line. Linux includes easy methods to perform these tasks:

Use the pipe character (|) to retrieve data from one program and “pipe” it to another program.
Use a single greater-than bracket (>) to create a new file if the file does not already exist, or to overwrite any existing content if the file does exist.
Use a double greater-than bracket (>>) to create a new file if the file does not already exist, or to append the new data to the file if the file does exist.
Use a single less-than bracket (<) to send input from a file to a command.

The following are examples of how to combine tasks into a single command:

Command	Description
`grep User /usr/local/apache/conf/httpd.conf \| more`	This command searches for all of the lines in the `httpd.conf` file that match the `User` search term, and then prints the results to your terminal one screen at a time.
`last -a > /root/lastlogins.tmp`	This command prints all of the current login history to the `/root/lastlogins.tmp` file.
`mysql --skip-column-names --batch -e 'show processlist' \| wc -l`	This command lists the number of MySQL® threads. If subselect expressions start new threads, the output of the show `processlist` command includes them.
`netstat -an \| grep :80 \| wc -l`	This command shows the number of active connections to Apache®. Apache’s `httpd` daemon runs on port `80`.
`tail -10000 /var/log/exim_mainlog \| grep 'example\.com' \| more`	This command finds the last 10,000 lines from the `/var/log/exim_mainlog` file, searches those lines for all occurrences of the string `example.com`, and then prints the search results to your terminal one screen at a time. Note: The system treats periods (`.`) in a command as wildcard characters. Precede each period with a backslash (`\`) to instruct grep to interpret the period literally.

Common configuration files and directories

You can find common configuration files and directories in the following locations on your server:

Service	Locations
Exim	`/etc/exim.conf` `/var/log/exim_mainlog` `/var/log/exim_rejectlog` `/etc/valiases/` `/etc/vfilters/` `/home/username/.forward`
MySQL	`/root/.my.cnf` `/etc/my.cnf` `/var/lib/mysql/`
ProFTPD	`/etc/proftpd.conf` `/var/log/xferlog` `/etc/proftpd/`
SSH	`/etc/ssh/sshd_config`
System	`/var/log/messages` `/var/log/dmesg`