Here, we list the most important Linux commands every user should know

1. pwd command
Use the pwd command to find out the path of the current working directory (folder) you’re in. The command will return an absolute (full) path, which is basically a path of all the directories that starts with a forward slash (/).

2. cd command
To navigate through the Linux files and directories, use the cd command. It requires either the full path or the name of the directory, depending on the current working directory that you’re in.
There are some shortcuts to help you navigate quickly:
    cd .. (with two dots) to move one directory up
    cd to go straight to the home folder
    cd- (with a hyphen) to move to your previous directory

3. ls command
The ls command is used to view the contents of a directory. By default, this command will display the contents of your current working directory.
If you want to see the content of other directories, type ls and then the directory’s path. For example, enter ls /home/username/Documents to view the content of Documents.
There are variations you can use with the ls command:
    ls -R will list all the files in the sub-directories as well
    ls -a will show the hidden files
    ls -al will list the files and directories with detailed information like the permissions, size, owner, etc.

4. cat command
cat (short for concatenate) is one of the most frequently used commands in Linux. It is used to list the contents of a file on the standard output (sdout). To run this command, type cat followed by the file’s name and its extension. For instance: cat file.txt.
Here are other ways to use the cat command:
    cat > filename creates a new file
    cat filename1 filename2>filename3 joins two files (1 and 2) and stores the output of them in a new file (3)
to convert a file to upper or lower case use, cat filename | tr a-z A-Z >output.txt

5. cp command
Use the cp command to copy files from the current directory to a different directory. For instance, the command cp scenery.jpg /home/username/Pictures would create a copy of scenery.jpg (from your current directory) into the Pictures directory.

6. mv command
The primary use of the mv command is to move files, although it can also be used to rename files.
The arguments in mv are similar to the cp command. You need to type mv, the file’s name, and the destination’s directory. For example: mv file.txt /home/username/Documents.
To rename files, the Linux command is mv oldname.ext newname.ext

7. mkdir command
Use mkdir command to make a new directory — if you type mkdir Music it will create a directory called Music.
There are extra mkdir commands as well:
To generate a new directory inside another directory, use this Linux basic command mkdir Music/Newfile
use the p (parents) option to create a directory in between two existing directories. For example, mkdir -p Music/2020/Newfile will create the new “2020” file.

8. rmdir command
If you need to delete a directory, use the rmdir command. However, rmdir only allows you to delete empty directories.

9. rm command
The rm command is used to delete directories and the contents within them. If you only want to delete the directory — as an alternative to rmdir — use rm -r.
Note: Be very careful with this command and double-check which directory you are in. This will delete everything and there is no undo.

10. touch command
The touch command allows you to create a blank new file through the Linux command line. As an example, enter touch /home/username/Documents/Web.html to create an HTML file entitled Web under the Documents directory.

11. locate command
You can use this command to locate a file, just like the search command in Windows. What’s more, using the -i argument along with this command will make it case-insensitive, so you can search for a file even if you don’t remember its exact name.
To search for a file that contains two or more words, use an asterisk (*). For example, locate -i school*note command will search for any file that contains the word “school” and “note”, whether it is uppercase or lowercase.

12. find command
Similar to the locate command, using find also searches for files and directories. The difference is, you use the find command to locate files within a given directory.
As an example, find /home/ -name notes.txt command will search for a file called notes.txt within the home directory and its subdirectories.
Other variations when using the find are:
To find files in the current directory use, find . -name notes.txt
To look for directories use, / -type d -name notes. txt

13. grep command
Another basic Linux command that is undoubtedly helpful for everyday use is grep. It lets you search through all the text in a given file.
To illustrate, grep blue notepad.txt will search for the word blue in the notepad file. Lines that contain the searched word will be displayed fully.

14. sudo command
Short for “SuperUser Do”, this command enables you to perform tasks that require administrative or root permissions. However, it is not advisable to use this command for daily use because it might be easy for an error to occur if you did something wrong.

15. df command
Use df command to get a report on the system’s disk space usage, shown in percentage and KBs. If you want to see the report in megabytes, type df -m.

16. du command
If you want to check how much space a file or a directory takes, the du (Disk Usage) command is the answer. However, the disk usage summary will show disk block numbers instead of the usual size format. If you want to see it in bytes, kilobytes, and megabytes, add the -h argument to the command line.

17. head command
The head command is used to view the first lines of any text file. By default, it will show the first ten lines, but you can change this number to your liking. For example, if you only want to show the first five lines, type head -n 5 filename.ext.

18. tail command
This one has a similar function to the head command, but instead of showing the first lines, the tail command will display the last ten lines of a text file. For example, tail -n filename.ext.

19. diff command
Short for difference, the diff command compares the contents of two files line by line. After analyzing the files, it will output the lines that do not match. Programmers often use this command when they need to make program alterations instead of rewriting the entire source code.
The simplest form of this command is diff file1.ext file2.ext

20. tar command
The tar command is the most used command to archive multiple files into a tarball — a common Linux file format that is similar to zip format, with compression being optional.

This command is quite complex with a long list of functions such as adding new files into an existing archive, listing the content of an archive, extracting the content from an archive, and many more. Check out some practical examples to know more about other functions.

21. chmod command
chmod is another Linux command, used to change the read, write, and execute permissions of files and directories. As this command is rather complicated, you can read the full tutorial in order to execute it properly.

22. chown command
In Linux, all files are owned by a specific user. The chown command enables you to change or transfer the ownership of a file to the specified username. For instance, chown linuxuser2 file.ext will make linuxuser2 as the owner of the file.ext.

23. jobs command
jobs command will display all current jobs along with their statuses. A job is basically a process that is started by the shell.

24. kill command
If you have an unresponsive program, you can terminate it manually by using the kill command. It will send a certain signal to the misbehaving app and instructs the app to terminate itself.
There is a total of sixty-four signals that you can use, but people usually only use two signals:

    SIGTERM (15) — requests a program to stop running and gives it some time to save all of its progress. If you don’t specify the signal when entering the kill command, this signal will be used.
    SIGKILL (9) — forces programs to stop immediately. Unsaved progress will be lost.

Besides knowing the signals, you also need to know the process identification number (PID) of the program you want to kill. If you don’t know the PID, simply run the command ps ux.

After knowing what signal you want to use and the PID of the program, enter the following syntax:

kill [signal option] PID.

25. ping command

Use the ping command to check your connectivity status to a server. For example, by simply entering ping google.com, the command will check whether you’re able to connect to Google and also measure the response time.


summary:

Here, we stated the basic 25 Linux command every user should know.