How to Change the Default Command-Line Text Editor in Ubuntu Using update-alternatives

When running system administration tools such as crontab -e, visudo, git commit, or systemctl edit in Ubuntu, the operating system launches a command-line text editor to handle the file revision. By default, Ubuntu assigns GNU nano as the system-wide editor. While nano provides a gentle learning curve for beginners, experienced developers and sysadmins often prefer Vim, Neovim, or Micro.

Ubuntu manages default binary selections through the update-alternatives system, which maintains symbolic links in /etc/alternatives/ to ensure commands reference your favoured software.

Changing the System-Wide Default Editor

To configure your preferred editor across all administrative commands:

1. Open your terminal in Ubuntu.
2. Execute the following configuration command:

   sudo update-alternatives --config editor

3. The terminal will print a numbered menu of all text editors currently installed on your system:

   There are 4 choices for the alternative editor (providing /usr/bin/editor).
   
     Selection    Path                Priority   Status
   ------------------------------------------------------------
   * 0            /bin/nano            40        auto mode
     1            /bin/ed             -100       manual mode
     2            /bin/nano            40        manual mode
     3            /usr/bin/vim.basic   30        manual mode
     4            /usr/bin/vim.tiny    15        manual mode
   
   Press <enter> to keep the current choice[*], or type selection number: 

4. Type the number corresponding to your preferred editor (for example, 3 for standard Vim) and press Enter.

Testing Your New Default Editor

Verify that your selection took effect by invoking the generic editor wrapper:

editor /tmp/testfile.txt

The chosen program should open immediately. Close or quit the editor when finished.

Setting the Editor for a Specific User via Environment Variables

If you do not possess root or sudo privileges, or if multiple users share the same server with differing editor preferences, configure your user profile environment variables:

1. Open your shell configuration file in your home directory:

   nano ~/.bashrc

2. Scroll to the end of the file and export the SELECTED_EDITOR, EDITOR, and VISUAL variables:

   export EDITOR="/usr/bin/vim"
   export VISUAL="/usr/bin/vim"

3. Save the file and apply the changes immediately:

   source ~/.bashrc

Commands that query POSIX environment standards will now respect your personal selection without affecting other system accounts.