On my Ubuntu OS, I see this in `/etc/vim/vimrc.tiny`:

```
$ cat /etc/vim/vimrc.tiny
" Vim configuration file, in effect when invoked as "vi".

```

Here's the partial output from `:version`:  

`system vimrc file: "$VIM/vimrc"` 

It looks like the VIM environment variable is not defined - `echo $VIM` doesn't show anything.

So how does `vi` know to read `/etc/vim/vimrc.tiny`?