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Basic Linux/Unix commands

In this document, we go through some of the most basic Linux commands. These commands can be used in the shell (the command line terminal) to get full use of your remote server. Most of these commands will be compatible with all UNIX OSes. However, depending on the version, the arguments (the parameters after the basic command) used may change.

cd: Change directory

The cd allows you to change the directory you are in on your shell.

For example, you are in your personal directory (home) and you want to navigate to the directory where your log files are (/var/log). Enter the following command:

cd /var/log/

You are now in the /var/log directory.

ls: List the content of a directory

This command allows you to display all the contents of a directory.

You are still in the /var/log directory, and you want to see everything it contains. Enter the ls command. A list of the contents displays as output:

alternatives.log        alternatives.log.7.gz  apport.log.5.gz  auth.log.4.gz  dmesg.0        dpkg.log.3.gz  fontconfig.log   kern.log.3.gz          pm-powersave.log.4.gz  syslog.2.gz          upstart
alternatives.log.1 alternatives.log.8.gz apport.log.6.gz boot.log dmesg.1.gz dpkg.log.4.gz fsck kern.log.4.gz pm-suspend.log syslog.3.gz wtmp
alternatives.log.10.gz alternatives.log.9.gz apport.log.7.gz bootstrap.log dmesg.2.gz dpkg.log.5.gz gpu-manager.log lastlog pm-suspend.log.1 syslog.4.gz wtmp.1

You can also perform a ls on another folder:

ls /etc 
Tip:

To get a more detailed view of the files in a directory, type ls -l, or use the abbreviated command ll. This displays additional details such as file permissions, dates and sizes.

rm: Remove (delete) folders and files

To delete data, you need the command rm. Type rm followed by the name of the file you want to delete:

rm myFile

To delete folders as opposed to files, you need to add the -r argument:

rm -r myFolder

This will recursively remove all files and content in the folder, and the folder itself

Tip:

To force a deletion, use rm -rf myFolder. Pay attention when using this command. A mistake can delete critial data without asking you for confirmation.

man: User manual

In Linux everything is documented! If you want to know how a certain program works, or want to know all its possibilities, man will give you the answer.

The usage is pretty simple:

man COMMAND

For example: man ls will display all the details about the ls command we saw previously.

nano: File editor

At some point, you will probably need to edit a text file using the command line. The most simple way to do this is via the nano editor. Type nano followed by the name of the file you want to edit (if you are in the same directory as the file) or the path to the file (if the file is in another directory):

nano /path/to/myFile.txt

The nano text editor displays, and you can make your edits. When you have finished, terminate nano by pressing the keys CTRL + X. If you made any changes, you will be prompted to save them.

Once you have finished to edit your file, terminate nano by pressing the keys: ”CTRL + X”

If you made any changes, you will be asked to save them.