Debian and Ubuntu uses for visudo, crontab and other similar applications the default text editor, you want to change it use the update-alternatives command.
It is as easy as, run this on a terminal window.
sudo update-alternatives –config editor
The options in my Debian system are:
There are 6 alternatives which provide `editor’.
Selection Alternative
———————————————–
1 /bin/ed
2 /bin/nano
3 /usr/bin/vim.tiny
*+ 4 /usr/bin/vim.gnome
5 /usr/bin/mcedit-debian
6 /usr/bin/emacs21
Press enter to keep the default[*], or type selection number:
The + sign denotes the default option, and the * sign denotes the actual selection, to change from vim to nano, just press 2 in this example and the ENTER.
Now all applications that uses an editor will use the new default one.