This quick reference helps you get familiar with the following basic Linux commands:

1. Application and process management:
   • which – Get the full path to a command’s executable file.
   • yum – Search for, install, remove, and update packages and dependencies for Fedora, CentOS, and Red Hat Enterprise Linux (RHEL).
2. Console and output management:
   • cat – Display file contents on the terminal.
   • clear – Clear the terminal display. 
   • echo – Print text or variables in the terminal.
   • top – Get information about running processes.
3. Creating and exporting environment variables:
   • env – Display all environment variables running on the system.
   • export – Export environment variables.
   • printenv – Print a particular environment variable to the console.
   • source – Execute commands stored in a file from within the current shell, or refresh environment variables.
4. Working with files and directories:
   • cd – Change to another directory.
   • cp – Copy the contents of the source directory or file to a target directory or file.
   • find – Locate a file or directory by name.
   • grep – Search for a string within an output.
   • ls – List the contents of a directory.
   • mkdir – Create directories.
   • more – View and traverse the content of a file or stdout.
   • mv – Move or rename files.
   • pwd – Get the name of the present working directory.
   • rm – Delete files or directories.
   • tar – Extract and compress files.
5. Accessing command-line help documentation:
   • man – Access manual pages for all Linux commands.
6. Working with networks on and from a Linux computer:
   • curl – Get or post a file to or from the Internet according to a URL.
   • ip – Gets the IP information for the physical or virtual machine.
   • netstat – Get information about network connections and more.
   • ssh – Establish a secure encrypted connection between two hosts over an insecure network.
   • wget – Direct download files from the Internet.
7. Process management:
   • && – Execute commands in a sequence.
   • kill – Removes a running process from memory.
   • ps – Display active processes.
8. System control:
   • poweroff – Shut down a computer.
   • restart – Restart a computer.
9. User management:
   • whoami – Display the user ID.
   • sudo find <starting/directory> -name <file/directory name> – Finds a file or directory by name.

Excerpt

user add

adduser [options] <username>

Adds a user to the computing environment. The command must be run as sudo in order
to have administrator access.

Example:
The following example adds a user with the login name cooluser. The HOME directory
home/cooluser is created by default. Then, the example invokes the command
passwd to set a password for the new user:

$ sudo adduser cooluser

$ sudo passwd cooluser
Changing password for user cooluser.
New password:
Retype new password:
passwd: all authentication tokens updated successfully.