20 Essential Linux Commands You Should Know

What you need before you start

• A VPS running Linux, e.g. Ubuntu or Debian.
• An SSH client to connect to the server. More: How to use PuTTY.
• A user with root or sudo privileges.

Commands

1. Moving between directories

   ls lists the files and folders in a directory. With -l you’ll see size, date and permissions:

   ls -lCopy

   Add -a to also see hidden files (starting with a dot):

   ls -laCopy

   cd changes the current directory:

   cd /home/user/DocumentsCopy

   Go up one directory:

   cd ..Copy

   pwd shows the full path of the directory you’re in:

   pwdCopy
   Tried it

2. Files and folders

   mkdir creates a new folder:

   mkdir new-folderCopy

   With -p it also creates any missing parent folders:

   mkdir -p projects/site/imagesCopy

   touch creates an empty file. If the file already exists, it updates its modification time:

   touch file.txtCopy

   cp copies a file:

   cp file.txt copy.txtCopy

   Copying a folder requires -r:

   cp -r folder1 folder2Copy

   mv moves a file to another folder:

   mv file.txt folder/Copy

   The same command is used to rename a file:

   mv old.txt new.txtCopy

   rm deletes a file:

   rm file.txtCopy

   Deleting a folder with all its contents requires -r:

   rm -r folder/Copy
   Be careful

   Linux has no recycle bin. Deleted files are gone for good, and a typo in a path with sudo rm -r can wipe the whole system.

   Tried it

3. File contents and search

   cat shows a file’s contents in the terminal:

   cat file.txtCopy

   nano opens a file in a simple terminal text editor:

   nano file.txtCopy
   How to save

   Ctrl + O and Enter saves the file, Ctrl + X exits the editor.

   grep searches for text in a file:

   grep "text" file.txtCopy

   With -r it searches all files in the current directory and subdirectories:

   grep -r "text" .Copy

   find finds files by name:

   find . -type f -name "file.txt"Copy

   Finding a folder:

   find . -type d -name "folder"Copy
   Tried it

4. Administration and software

   sudo runs a command with administrator privileges. Just put it in front of another command:

   sudo apt updateCopy

   apt manages software on Ubuntu and Debian. First update the package list and the system:

   sudo apt update && sudo apt upgradeCopy

   Installing a program:

   sudo apt install package-nameCopy

   chmod changes file and folder permissions. For example, the owner can do everything and others can only read and execute:

   chmod 755 script.shCopy

   The simplest way to make a script executable:

   chmod +x script.shCopy
   Tried it

5. Archives and disk

   tar creates a compressed archive:

   tar -czvf archive.tar.gz folder/Copy

   Extracts an archive:

   tar -xzvf archive.tar.gzCopy

   df shows how much disk space is used and free:

   df -hCopy

   To see how much space a specific folder takes, use du:

   du -sh folder/Copy
   Tried it

6. Processes and history

   ps shows all running processes:

   ps auxCopy

   Finding a specific process:

   ps aux | grep nginxCopy

   kill stops a process by its ID (PID), which you’ll see in the ps output:

   kill 12345Copy

   If the process won’t stop, force it:

   kill -9 12345Copy

   history shows previously entered commands:

   historyCopy
   Tried it

Practice

Try a few commands safely. This line creates a folder with a file inside, lists it and deletes everything:

The && symbols chain commands: the next one runs only if the previous one succeeded.