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Kickstart Your Linux Journey

Until now you've probably mainly experienced the GUI world - point, click, drag, and drop. You've clicked buttons and moved windows around like a pro! But things are going to change now. You're going to learn how to use the terminal and here's why it's great.

CLI Spells​

Goodbye Mouse, Hello Keyboard​

The reasons you would want to shift your focus to your keyboard shortcuts as well are:

  • You'll look cool, like in Mr. Robot
  • You can automate a whole bunch of processes
  • The more you practice, the faster and more natural it gets
  • You won't always have access to GUI, and you need to know how to talk with the system without it

The first and most important shortcut you're going to learn is Ctrl + Alt + t. As you can see, a misterious dark box is now on your screen.

This is called a terminal and is there to help us communicate with the operating system via text. The communication is based on commands, hence the terminal's actual name: Command-Line Interface (CLI).

Some other quick shortcuts you can try on the spot:

  • Ctrl + d: close the current window
  • Ctrl + Shift + c: copy text from the terminal
  • Ctrl + Shift + v: paste text to the terminal

The Prompt​

Every terminal has a prompt that lets us know about the directory we're in, who the user and hostname are and if it's ready to execute a command.

This is generally the format of the prompt with very little variation:

user@hostname:~$ cd Documents/
user@hostname:~/Documents$

More generally:

[USERNAME]@[HOSTNAME]:[PATH][SYMBOL]

User? Hostname? Symbol? What are you talking about?

  • [USERNAME] is the username of the current user. That's usually you, except when you run sudo su to access the root user.
  • [HOSTNAME] is your computer's name, which you set during system installation.
  • [PATH] is your current working directory. Every time you open a new terminal, the default directory is your home directory. ~ is shorthand for /home/YOURUSERNAME.
  • [SYMBOL] is $ for a normal user and # for root. This symbol can be customized.

You can verify all of the above by typing these commands in the terminal:

  • whoami to check the username
  • hostname to check the hostname
  • pwd to print the working directory
sirbu@pop-os:~$ whoami
sirbu
sirbu@pop-os:~$ sudo su
[sudo] password for sirbu:
root@pop-os:/home/sirbu# whoami
root
root@pop-os:/home/sirbu# exit
exit
sirbu@pop-os:~$ hostname
pop-os
sirbu@pop-os:~$ pwd
/home/sirbu
sirbu@pop-os:~$

Where am I?​

You may feel confused about directories and navigating through files in your system, but don't worry—everything is under control.

We need to know where we are in the file hierarchy, also called the file system. If Windows uses \ as a path separator, Linux uses /, and / also represents the root of the file system.

Linux File System

As you can see, everything has its place in the system and is navigable, like a map.

Moving between folders is called changing the directory.

Open a new terminal and try to see where you are. As mentioned earlier, the default path is ~ or /home/username. If you want to move somewhere else, use this command:

$ cd /path/to/new/location

For example, to move to Documents:

sirbu@pop-os:~$ cd Documents/
sirbu@pop-os:~/Documents$

Preview the contents of a folder​

You can list the contents of the current directory with the ls command (short for list):

sirbu@pop-os:~/Documents/FMI-UNIBUC$ ls
an_2  an_3  README.md
sirbu@pop-os:~/Documents/FMI-UNIBUC$

Every command can take many parameters, including ls. If you give a path as a parameter, you can "preview" the files that are there without leaving your current directory!

sirbu@pop-os:/$ ls #contents of "/" aka root directory
bin   dev  home  lib32  libx32      media  opt   recovery  run   srv  tmp  var
boot  etc  lib   lib64  lost+found  mnt    proc  root      sbin  sys  usr
sirbu@pop-os:/$ ls media/ #contents of media/
root  sirbu
TAB is your friend

Press TAB as much as you can.

If you give enough context, your command will be autocompleted.

For example, while being in ~, try typing cd Doc, press TAB, and your command will become cd Documents/

If the context is not clear enough, you will see all the options in the terminal:

sirbu@pop-os:~$ cd D
Desktop/   Documents/ Downloads/

To return to the previous folder or list its contents, use ..:

sirbu@pop-os:~$ ls ../ # contents of the parent directory
sirbu
sirbu@pop-os:~$ ls ../../ # contents of the "root" folder, two levels up
bin   dev  home  lib32  libx32      media  opt   recovery  run   srv  tmp  var
boot  etc  lib   lib64  lost+found  mnt    proc  root      sbin  sys  usr
sirbu@pop-os:~$ cd ../../ # now we'll be in the "root" folder!
sirbu@pop-os:/$ pwd
/
sirbu@pop-os:/$
note

The more you chain ../.., the higher you traverse the file structure.

Use your creator powers​

You can create a directory with mkdir:

sirbu@pop-os:~/demo$ mkdir dummy-folder
sirbu@pop-os:~/demo$ ls
dummy-folder
sirbu@pop-os:~/demo$ cd dummy-folder/
sirbu@pop-os:~/demo/dummy-folder$

Let's create files inside our newly made folder with touch:

sirbu@pop-os:~/demo/dummy-folder$ touch demo-file1
sirbu@pop-os:~/demo/dummy-folder$ touch demo-file2
sirbu@pop-os:~/demo/dummy-folder$ ls
demo-file1  demo-file2

Our files are kinda empty, so let's add some text:

sirbu@pop-os:~/demo/dummy-folder$ cat demo-file1 # output the contents of the file
sirbu@pop-os:~/demo/dummy-folder$ nano demo-file1 # a simple command-line text editor
sirbu@pop-os:~/demo/dummy-folder$ cat demo-file1
Write anything you want, it doesn't really matter.
sirbu@pop-os:~/demo/dummy-folder$

Move stuff around with mv:

sirbu@pop-os:~/demo/dummy-folder$ ls
demo-file1  demo-file2  folder2
sirbu@pop-os:~/demo/dummy-folder$ mv demo-file1 folder2/
sirbu@pop-os:~/demo/dummy-folder$ ls
demo-file2  folder2
sirbu@pop-os:~/demo/dummy-folder$ ls folder2/
demo-file1
sirbu@pop-os:~/demo/dummy-folder$

Copy files with cp:

sirbu@pop-os:~/demo/dummy-folder$ cp demo-file2 folder2/
sirbu@pop-os:~/demo/dummy-folder$ ls folder2/
demo-file1  demo-file2
sirbu@pop-os:~/demo/dummy-folder$ ls
demo-file2  folder2

Remove with rm:

sirbu@pop-os:~/demo/dummy-folder$ rm demo-file2
sirbu@pop-os:~/demo/dummy-folder$ ls
folder2
sirbu@pop-os:~/demo/dummy-folder$ rmdir folder2/
rm: cannot remove 'folder2/': Is a directory

If folder2 were empty, the command would have worked fine. Since it's not, we must pass -r (for --recursive) for it to work.

$ rm -r folder2/ # in this case, rm works as well

This man has all the info you need​

Extensive documentation is available for almost every Linux command and can be accessed with man command. Knowing how to read the manual is essential.

Let's try reading the page for cat.

$ man cat

Use:

  • ↑ and ↓ to scroll
  • Space to scroll one page down
  • /<string> for quick search
  • q to quit.

Root is the most important​

Linux systems have multiple levels of privilege, and your actions are limited by your privilege level.

Similar to the Administrator role in Windows, root is the boss and is required whenever you need to make decisions that could affect the system.

danger

The root role must be used with caution! You can damage your system irreversibly if you don't know what you're doing.

Shell operators​

Redirection operator >​

This is used to redirect the output of a command to a file. If the file exists, it will be overwritten.

sirbu@pop-os:~/demo$ cat demo-file
This is the original text!
sirbu@pop-os:~/demo$ echo "Some text" # write text to the terminal window
Some text
sirbu@pop-os:~/demo$ echo "Some text" > demo-file
sirbu@pop-os:~/demo$ cat demo-file
Some text
sirbu@pop-os:~/demo$

Pipe |​

This operator takes the output of one command and passes it as input to another command. It's used for chaining commands together.

sirbu@pop-os:~/demo$ ls | grep "folder"
dummy-folder
sirbu@pop-os:~/demo$ ls
demo-file  dummy-folder
sirbu@pop-os:~/demo$

Logical AND &&​

This operator is used to execute the second command only if the first command succeeds (returns exit code 0).

sirbu@pop-os:~/demo$ mkdir test-and && cd test-and
sirbu@pop-os:~/demo/test-and$

More Terminal Tricks​

  • use up arrow and down arrow to navigate between your commands
  • use sudo !! to execute the last command with admin rights

Further Reading​

References​