SU(1) User Commands SU(1)
su - change user ID or become super-user
su [options] [LOGIN]
su is used to become another user during a login session. Invoked
without a username, su defaults to becoming the super user. The
optional argument - may be used to provide an environment similar to
what the user would expect had the user logged in directly.
Additional arguments may be provided after the username, in which case
they are supplied to the users login shell. In particular, an argument
of -c will cause the next argument to be treated as a command by most
command interpreters. The command will be executed by the shell
specified in /etc/passwd for the target user.
You can use the -- argument to separate su options from the arguments
supplied to the shell.
The user will be prompted for a password, if appropriate. Invalid
passwords will produce an error message. All attempts, both valid and
invalid, are logged to detect abuse of the system.
The current environment is passed to the new shell. The value of $PATH
is reset to /bin:/usr/bin for normal users, or
/sbin:/bin:/usr/sbin:/usr/bin for the super user. This may be changed
with the ENV_PATH and ENV_SUPATH definitions in /etc/login.defs.
A subsystem login is indicated by the presence of a "*" as the first
character of the login shell. The given home directory will be used as
the root of a new file system which the user is actually logged into.
The options which apply to the su command are:
-c, --command SHELL
Specify a command that will be invoked by the shell using its -c.
-, -l, --login
Provide an environment similar to what the user would expect had the
user logged in directly.
When - is used, it must be specified as the last su option. The
other forms (-l and --login) do not have this restriction.
-s, --shell SHELL
The shell that will be invoked.
The invoked shell is choosen among (higest priority first):
The shell specified with --shell
If --preserve-environment is used, the shell specified by the
$SHELL environment variable.
The shell indicated in the /etc/passwd entry for the target
/bin/sh if a shell could not be found by any above method.
If the target user has a restricted shell (i.e. the shell field
of this users entry in /etc/passwd is not specified in
/etc/shell), then the --shell option or the $SHELL environment
variable wont be taken into account unless su is called by the
-m, -p, --preserve-environment
Preserve the current environment.
If the target user has a restricted shell, this option has no effect
(unless su is called by root).
This version of su has many compilation options, only some of which may
be in use at any particular site.
User account information.
Secure user account information.
login(1), login.defs(5), sh(1)
User Commands 02/25/2007 SU(1)