The Unbearable Lightness Of SU-ing

The 'su' command allows a user to take the identity of another user.

The 'su' executable file has to be SUID, and owned by 'root', in order to function properly.

Using 'su' with the '-' flag will cause the command to switch to the complete environment of the new user, including shell, home directory, etc. Without the '-' flag we keep the original environment, and only the effective UID is switched.