Skip site navigation (1)Skip section navigation (2)

FreeBSD Man Pages

Man Page or Keyword Search:
Man Architecture
Apropos Keyword Search (all sections) Output format
home | help
SU(1L)									SU(1L)

NAME
       su - run	a shell	with substitute	user and group IDs

SYNOPSIS
       su [-flmp] [-c command] [-s shell] [--login] [--fast] [--preserve-envi-
       ronment]	[--command=command] [--shell=shell] [-]	 [--help]  [--version]
       [user [arg...]]

DESCRIPTION
       This  manual  page documents the	GNU version of su.  su allows one user
       to temporarily become another user.  It runs a shell with the real  and
       effective  user	ID,  group ID, and supplemental	groups of USER.	 If no
       USER is given, the default is root, the super-user.  The	shell  run  is
       taken  from  USER's  password  entry,  or  /bin/sh if none is specified
       there.  If USER has a password, su prompts for the password unless  run
       by a user with real user	ID 0 (the super-user).

       By  default,  su	 does  not  change the current directory.  It sets the
       environment variables `HOME' and	`SHELL'	from the  password  entry  for
       USER,  and  if USER is not the super-user, sets `USER' and `LOGNAME' to
       USER.  By default, the shell is not a login shell.

       If one or more ARGs are given, they are passed as additional  arguments
       to the shell.

       su  does	 not handle /bin/sh or other shells specially (setting argv[0]
       to "-su", passing -c only to certain shells, etc.).

       On systems that have syslog, su can be compiled to report  failed,  and
       optionally successful, su attempts using	syslog.

       This program does not support a "wheel group" that restricts who	can su
       to super-user accounts, because that can	help fascist  system  adminis-
       trators hold unwarranted	power over other users.

   OPTIONS
       -c COMMAND, --command=COMMAND
	      Pass  COMMAND, a single command line to run, to the shell	with a
	      -c option	instead	of starting an interactive shell.

       -f, --fast
	      Pass the -f option to the	shell.	This probably only makes sense
	      with  csh	and tcsh, for which the	-f option prevents reading the
	      startup file (.cshrc).  With Bourne-like shells, the  -f	option
	      disables	filename  pattern  expansion, which is not a generally
	      desirable	thing to do.

       --help Print a usage message on standard	output and exit	 successfully.

       -, -l, --login
	      Make  the	shell a	login shell.  This means the following.	 Unset
	      all environment variables	except	`TERM',	 `HOME',  and  `SHELL'
	      (which  are  set	as  described above), and `USER' and `LOGNAME'
	      (which are set, even for the super-user,	as  described  above),
	      and set `PATH' to	a compiled-in default value.  Change to	USER's
	      home directory.  Prepend "-" to the shell's  name,  to  make  it
	      read its login startup file(s).

       -m, -p, --preserve-environment
	      Do  not  change  the environment variables `HOME', `USER', `LOG-
	      NAME', or	`SHELL'.  Run the shell	given in the environment vari-
	      able  `SHELL'  instead  of USER's	shell from /etc/passwd,	unless
	      the user running su is not the superuser	and  USER's  shell  is
	      restricted.  A restricted	shell is one that is not listed	in the
	      file /etc/shells,	or in a	compiled-in list if that file does not
	      exist.   Parts  of  what	this  option does can be overridden by
	      --login and --shell.

       -s, --shell shell
	      Run SHELL	instead	of USER's shell	from /etc/passwd,  unless  the
	      user  running  su	 is  not  the  superuser  and  USER's shell is
	      restricted.

       --version
	      Print version information	on standard output then	exit  success-
	      fully.

Why GNU	su does	not support the	wheel group (by	Richard	Stallman)
       Sometimes a few of the users try	to hold	total power over all the rest.
       For example, in 1984, a few users at the	MIT AI lab  decided  to	 seize
       power  by changing the operator password	on the Twenex system and keep-
       ing it secret from everyone else.  (I was able to thwart	this coup  and
       give  power  back  to  the users	by patching the	kernel,	but I wouldn't
       know how	to do that in Unix.)

       However,	occasionally the rulers	do tell	someone.  Under	the  usual  su
       mechanism,  once	 someone learns	the root password who sympathizes with
       the ordinary users, he can tell the rest.  The  "wheel  group"  feature
       would make this impossible, and thus cement the power of	the rulers.

       I'm on the side of the masses, not that of the rulers.  If you are used
       to supporting the bosses	and sysadmins in whatever they do,  you	 might
       find this idea strange at first.

FSF			      GNU Shell	Utilities			SU(1L)

NAME | SYNOPSIS | DESCRIPTION | Why GNU su does not support the wheel group (by Richard Stallman)

Want to link to this manual page? Use this URL:
<http://www.freebsd.org/cgi/man.cgi?query=su&manpath=Linux+Slackware+3.1>

home | help