$EDITOR

The System's default text editor can be defined within /etc/profile. It's given the variable EDITOR.

Add these lines to /etc/profile.d/local.sh:

1
2export EDITOR=vim
3
4export VISUAL=$EDITOR

Then reload that profile with:

1source /etc/profile

If you want to ensure nano never appears again:

1sudo ln -sf $(which vim) $(which nano)