Ubuntu Common Commands

1. Sudo

$ sudo: SuperUser DO

Sudo allows you to run programs or other commands with administrative privileges, just like “Run as administrator” in Windows.

2. Apt-Get

Apt-get is used to install, update, upgrade and remove any package. Here is the list of different apt-get commands:

2.1 Sudo apt-get update

$ sudo apt-get update

Apt-get update with super user privileges is the first command you need to run in any Linux system after a fresh install. This command updates the database and let your system know if there are newer packages available or not.

2.2 Sudo apt-get upgrade

$ sudo apt-get upgrade
$ sudo apt-get upgrade <package-name>

After updating the package database, next step is to to upgrade the installed packages. And if you like to upgrade a particular package, you should tweak the above command, and replace the with your desired package.

2.3 Sudo apt-get upgrade

$ sudo apt-get install
$ sudo apt-get install <package-name>

Install some packages.

2.4 Sudo apt-get remove

$ sudo apt-get remove
$ sudo apt-get remove <package-name>

Sudo apt-get remove removes package. You only have to know the exact package name of the software you want to uninstall. If you don’t know the package name, use below command to list all the packages installed on your system and then copy the package name you want to remove:

$ dpkg --list

2.5 Sudo apt-get purge

$ sudo apt-get purge

It is used to remove a software completely from your system with its configuration or data files so that no longer personalized settings will be available during reinstallation.

2.6 Sudo apt-get autoremove

$ sudo apt-get autoremove

It is used to remove any unnecessary packages. Unnecessary means, whenever you install an application, the system will also install the software that this application depends on. It is common in Ubuntu that applications share the same libraries. When you remove the application the dependency will stay on your system. So it’s used to remove unwanted software dependencies after uninstalling a package.

3. Ls [1]

ls (list) command lists all files and folders in your current working directory. You can also specify paths to other directories if you want to view their contents.

$ ls

List the contents of the current working directory

$ ls [directory path here]

List the contents of another directory:

$ ls /

List the contents of the root directory

$ ls ..

List the contents of the parent directory one level above.

$ ls ../..

List the contents of the parent directory two levels above.

$ ls ~

List the contents in the users’s home directory

$ ls -d */

List only directories

$ ls *

List the contents of the directory with it’s subdirectories.

$ ls -s (the s is lowercase)

List files or directories with their sizes

$ ls -l (list files in long format)

List the contents of the directory in a table format with columns including:

content permissions
number of links to the content
owner of the content
group owner of the content
size of the content in bytes
last modified date / time of the content
file or directory name

$ ls -lh (List files in long format with readable file sizes)

List the files or directories in the same table format above, but with another column representing the size of each file/directory

$ ls -a

List files or directories including hidden files or directories. In Linux, anything that begins with a is considered a hidden file.

$ ls -l -a or ls -a -l or ls -la or ls -al

List files or directories in a table format with extra information including hidden files or directories

$ ls -t

List files or directories and sort by last modified date and time in descending order (biggest to smallest). You can also add a -r flag to reverse the sorting order like so: ls -tr

$ ls -S (the S is uppercase)

List files or directories and sort by date or time in descending order (biggest to smallest). You can also add a -r flag to reverse the sorting order like so: ls -Sr

$ ls > output.txt

Print the output of the preceding command into an output.txt file. The key point here is that the result will be outputted into a file and not logged to the command line. Then you can use the file, or log the contents of the file with cat output.txt

4. Cd

$ cd <folder name> Cd (change director”) Linux command is used to change the current working directory.  Some common uses are:

$ cd /  – Takes you to the root directory.
$ cd .. – Takes you up one directory level.
$ cd –  – Takes you to the previous directory.

5. Pwd

$ Pwd

Print working directory displays the full pathname of the current working directory.

6. Cp

$ cp cp (copy) Linux command allows you to copy a file.

You should specify both the file you want to be copied and the location you want it copied to For example, cp xyz /home/myfiles would copy the file “xyz” to the directory “/home/myfiles”.

7. Mv

$ mv (move) command allows you to move files.

You can also rename files by moving them to the directory they are currently in, but under a new name. The usage is the same as cp. For example mv xyz /home/myfiles would move the file “xyz” to the directory “/home/myfiles”.

8. Rm

$ rm (remove) command removes the specified file.

rmdir (“remove directory”) – Removes an empty directory. rm -r (“remove recursively”) – Removes a directory along with its content.

9. Touch

$ touch file1.txt

If the file file1.txt doesn’t exist the command above will create it, otherwise, it will change its timestamps.

$ touch file1.txt file2.txt file3.txt

Create multiple files at once, specify the file names separated by space.

10. Cat

Cat(concatenate) command reads data from the file and gives their content as output. It helps us to create, view, concatenate files.

$ cat filename

View a single file.

$ cat file1 file2

View multiple files.

$ cat -n filename

View contents of a file preceding with line numbers.

$ cat > newfile

Create and a file named newfile.

$ cat [filename-whose-contents-is-to-be-copied] > [destination-filename]

The content will be copied in destination file.

$ cat file1 >> file2

Append the contents of one file to the end of another file.

11. Mkdir

$ mkdir (make directory) Allows you to create a new directory.

You can specify where you want the directory created – if you do not do so, it will be created in your current working directory.

12. History

$ history

history command displays all of your previous commands up to the history limit.

13. Df

$ df: display filesystem

It displays information about the disk space usage of all mounted filesystems.

14. Passwd

$ passwd
$ passwd <user>

It is used to change user password using Terminal. What you have to do is run the above command, where is the username whose password has to change.

15. Shortcuts

Ctrl + Shift + T: Open new tab on current terminal
Ctrl + Shift + W: Close the current tab
Ctrl + A: Move cursor to beginning of line
Ctrl + E: Move cursor to end of line
Ctrl + U: Clears the entire current line
Ctrl + K: Clears the command from the cursor right
Ctrl + W: Delete the word before the cursor
Ctrl + R: Allows you to search your history for commands matching what you have typed
Ctrl + C: Kill the current process
Ctrl + Z: Suspend the current process by sending the signal SIGSTOP
Ctrl + L: Clears the terminal output
Alt + F: Move forward one word
Alt + B: Move backward one word
Ctrl + Shift + C: Copy the highlighted command to the clipboard
Ctrl + Shift + V or Shift + Insert: Paste the contents of the clipboard
Up/Down Arrow keys: To scroll through your command history, allowing you to quickly execute the same command multiple times

Reference

[1] https://www.freecodecamp.org/news/the-linux-ls-command-how-to-list-files-in-a-directory-with-options/#:~:text=The%20ls%20command%20is%20used,them%20via%20the%20command%20line

[2] https://www.tecmint.com/15-basic-ls-command-examples-in-linux/

[3] https://techlog360.com/basic-ubuntu-commands-terminal-shortcuts-linux-beginner/

Share some common commands and shortcuts of Ubuntu