su man page on Archlinux

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SU(1)				 User Commands				 SU(1)

       su - run a command with substitute user and group ID

       su [options] [-] [user [argument...]]

       su allows to run commands with a substitute user and group ID.

       When  called  without  arguments, su defaults to running an interactive
       shell as root.

       For backward compatibility su defaults to not change the current direc‐
       tory  and  to  only  set the environment variables HOME and SHELL (plus
       USER and LOGNAME if the target user is not root).  It is recommended to
       always use the --login option (instead of its shortcut -) to avoid side
       effects caused by mixing environments.

       This version of su uses PAM for	authentication,	 account  and  session
       management.   Some  configuration options found in other su implementa‐
       tions, such as support of a wheel group, have to be configured via PAM.

       -c, --command=command
	      Pass command to the shell with the -c option.

	      Same as -c but do not create a new session (discouraged).

       -f, --fast
	      Pass -f to the shell, which may or may not be useful,  depending
	      on the shell.

       -g, --group=group
	      Specify  the  primary  group.   This option is available for the
	      root user only.

       -G, --supp-group=group
	      Specify a supplemental group.  This option is available for  the
	      root user only.

       -, -l, --login
	      Starts the shell as login shell with an environment similar to a
	      real login:

		 o	clears all environment variables except TERM

		 o	initializes the	 environment  variables	 HOME,	SHELL,

		 o	changes to the target user's home directory

		 o	sets  argv[0] of the shell to '-' in order to make the
			shell a login shell

       -m, -p, --preserve-environment
	      Preserves the whole environment, i.e.  it	 does  not  set	 HOME,
	      SHELL,  USER  nor LOGNAME.  This option is ignored if the option
	      --login is specified.

       -s, --shell=shell
	      Runs the specified shell instead of the default.	The  shell  to
	      run is selected according to the following rules, in order:

		 o	the shell specified with --shell

		 o	the shell specified in the environment variable SHELL,
			if the --preserve-environment option is used

		 o	the shell listed in the passwd	entry  of  the	target

		 o	/bin/sh

	      If  the  target  user has a restricted shell (i.e. not listed in
	      /etc/shells), the --shell option and the SHELL environment vari‐
	      ables are ignored unless the calling user is root.

       --help Display help text and exit.

	      Display version information and exit.

       Upon  receiving	either	SIGINT,	 SIGQUIT or SIGTERM, su terminates its
       child and afterwards terminates itself with the received signal.

       su reads the /etc/default/su and /etc/login.defs	 configuration	files.
       The following configuration items are relevant for su(1):

       FAIL_DELAY (number)
	   Delay in seconds in case of authentication failure.	Number must be
	   a non-negative integer.

       ENV_PATH (string)
	   Defines the PATH environment variable  for  a  regular  user.   The
	   default value is /usr/local/bin:/bin:/usr/bin.

       ENV_ROOTPATH (string)
       ENV_SUPATH (string)
	   Defines  the PATH environment variable for root.  The default value
	   is /usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin.

       ALWAYS_SET_PATH (boolean)
	   If set to yes and --login and --preserve-environment were not spec‐
	   ified su initializes PATH.

       su normally returns the exit status of the command it executed.	If the
       command was killed by a signal, su returns the  number  of  the	signal
       plus 128.

       Exit status generated by su itself:

		 1	Generic error before executing the requested command

		 126	The requested command could not be executed

		 127	The requested command could was not found

       /etc/pam.d/su	default PAM configuration file
       /etc/pam.d/su-l	PAM configuration file if --login is specified
       /etc/default/su	command specific logindef config file
       /etc/login.defs	global logindef config file

       For  security reasons su always logs failed log-in attempts to the btmp
       file, but it does not write to the lastlog file at all.	This  solution
       allows to control su behavior by PAM configuration.  If you want to use
       the pam_lastlog module to print warning	message	 about	failed	log-in
       attempts	 then  the  pam_lastlog has to be configured to update lastlog
       file too. For example by:

	      session  required nowtmp

       runuser(8), pam(8), shells(5), login.defs(5)

       Derived from coreutils' su which was based on  an  implementation  from
       David MacKenzie.

       The  su command is part of the util-linux package and is available from
       Linux   Kernel	Archive	   ⟨

util-linux			 October 2013				 SU(1)

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