Linux Command for your reference

In this post, I will give the list of Linux command you need to use in your Linux machine. Below I will categorize the Linux command into a few different topics for your understanding.

Miscellaneous

echo	Display a line of text. Often used in programs and scripts to relay information to users.
factor	Displays possible factors of a decimal number.
expr	Solve math equations.
look	Look up a word in the dictionary.

Terminal

clear	Clear the terminal screen.
history	Display recently used commands. You can also view these commands via the Up and Down keys.
!	Repeat a recently used command. You can use !n to repeat the n-th command in history or !-n to repeat what happened n commands ago.
man	Display the manual for a terminal program.
whatis	Display a brief description of a terminal program. A simpler alternative to the man command.
alias	Create a shortcut to a command or, when combined with the cd command, directory.
exit	Exit or close the terminal.

Navigation & File Management

cd	Change directory. Used to navigate between folders.
pwd	Display current directory.
cd	Change current directory.
ls	Display a list of files in the current directory.
cp	Makes a copy of a file. Defaults to the current directory unless you specify a specific one.
mv	Move a file from one directory to another.
rm	Remove a file or set of files.
stat	Display when a file was last accessed, modified, or changed.
touch	Change the date accessed or date modified time of a given file to right now.
rmdir	Delete a file or files.
mkdir	Create a directory. Defaults to the current directory, but you can also specify one.
rmdir	Delete a directory. Defaults to the current directory, but you can also specify one. The target directory must be completely empty.
rename	Change the name of a file or set of files.
find	Search a specific directory (or your entire PC) to find files that match designated criteria.
locate	Search for files or directories. Faster than the find command, but has fewer options.
grep	Search a specific file or set of files to see if a string of text exists and where.
mount	Attach a separate filesystem (such as an external hard drive or USB stick) to your system's main filesystem.
umount	Detach a separate filesystem from your system's main filesystem.
cat	Display the contents of a text file. Also works with multiple files.
chmod	Modify the read, write, and execute permissions of a file.
chown	Change the user or group that owns a file.

Users

su	Switch user. Unless you desigate a specific user, this command will attempt to sign in as the root user (which you can think of as the system administrator).
whoami	Displays the current user name.
id	Display current user and group.
passwd	Create or update a user's password.

Network Management

ip	Displays you IP address, network interfaces, bandwidth usage, and more.
ping	Send or receive data from another computer on a network. Often used to test whether a network connection is established and the speed of that connection.
dig	Look up a domain's DNS address
wget	Download a file.
ssh	Secure Shell. Connect and login to a remote network location.

System Administration

uname	Displays core system information such as kernel version, hardware, and operating system.
sudo	Enter before a command to perform the command as a system administrator. User must have administrator priveleges for this to work.
apt/dnf/pacman	Programs for installing software and updates. Which one to use depends on your Linux-based operating system. Each requires administrator rights and additional instructions, such as sudo apt install program-name .
jobs	Display the status of all current jobs. A job is a representation of a running process or group of processes.
bg	Send a job to the background.
fg	Send a job to the foreground.
kill	End a process according to its process ID (which you can get using the ps command.
killall	End all processes whose names match your query.
ps	Display a list of running processes. Defaults to processes started by the current user.
top	Displays a list of running processes, sorted by how much CPU each uses. Unlike ps, the command updates in real-time.
uptime	Displays time since last boot.
whereis	Finds the executable file for a program.
df	Displays how much disk space is used and free on your system.
free	Displays how much RAM is used and free on your system.