To display the line numbers when editing a file with vi simply type the following during the edit.
[quickcode:noclick]:se nu[/quickcode]

Once line numbers are set then to remove the listing of numbers down the left hand column type the following.
[quickcode:noclick]:se nu![/quickcode]

VI Example: Displaying Line Numbers

Useful VI references.

Learning the vi and Vim Editors

Arnold Robbins. O’Reilly Media 2008, Paperback, 470 pages, $19.08

Hacking Vim

Kim Schulz. Packt Publishing 2007, Paperback, 228 pages, $30.45