The default text editor in installations of Debian and its derivatives is Nano, largely because it’s a simple and small editor. If you’re a Vim user, you might find it a little jarring to be presented with a modeless editor when you run commands like visudo or vipw.

Debian’s alternatives system makes this reasonably easy to adjust. If you have Vim installed, it should be available as one of the possible implementations of the editor alternative. You can check this with the update-alternatives command:

# update-alternatives --list editor
/bin/ed
/usr/bin/nano
/usr/bin/vim.basic

This shows that Vim is available as an alternative with /usr/bin/vim.basic, so you can update the symlink structure that defines the default editor like so:

# update-alternatives --set editor /usr/bin/vim.basic
... using /usr/bin/vim.basic to provide /usr/bin/editor (editor) in manual mode.

Now if you fire up visudo, vipw, or sudo -e you should find that Vim is fired up instead of the editor you didn’t want.

On my own workstation I have the latest Vim compiled from Mercurial and installed into /usr/local via checkinstall, so I had to add this to the alternatives system before I could use it:

# update-alternatives --install /usr/bin/editor editor /usr/local/bin/vim 200 \
    --slave /usr/share/man/man1/editor.1.gz editor.1.gz /usr/local/share/man/man1/vim.1.gz
# update-alternatives --set editor /usr/local/bin/vim
... using /usr/bin/vim.basic to provide /usr/bin/editor (editor) in manual mode.

Other relevant alternatives include the vi implementation for your system, which of course may not necessarily be Vim; some operating systems install the smaller and more vi-faithful nvi.