Command:   su - temporarily log in as superuser or another user
Syntax:    su [name]
Flags:     (none)
Examples:  su                       # Become superuser
           su ast                   # Become ast

     Su can be used to temporarily login as another  user.   It  prompts
for  the  superuser  password.   If  the correct password is entered, su
creates a shell with the desired uid.  If no name is specified, root  is
assumed.   To  exit  the  temporary  shell, type CTRL-D.  When memory is
tight, it is better to become superuser by logging out and then  logging
in again as root, rather than using su since the latter creates an extra
shell in memory.  Any user  with  a  zero  group  id  need  not  type  a
password.  This makes life easier for the system administrator.