The vi/vim configuration file is located @ $HOME/.exrc. of it does not exist, just create it.

$HOME/.exrc

:set number
:set ts=2

Your vi now will have tab size = 2 and line number is shown.
 

More useful settings

• :set – all Display all Set options
• :set autoindent – Indent following lines to the indentation of previous line.
• :set ts=4 – set tab stop to 4 char
• :set ignorecase – Ignore case during pattern matching.
• :set list – Show special characters in the file.
• :set number – Display line numbers.
• :set shiftwidth=n – Width for shifting operators << and >>
• :set showmode – Display when in Insert, Append, or Replace mode.
• :set wrapmargin=n – Set right margin 80-n for autowrapping lines (inserting newlines). 0 turns it off.

Done =)

Reference: how to change the tab size in vi?