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SU(1)			FreeBSD	General	Commands Manual			 SU(1)

     su	-- substitute user identity

     su	[-fKLlm] [-a auth-type]	[-c login-class] [-s login-shell]
	[login [shell arguments]]

     The su utility allows a user to run a shell with the user and group ID of
     another user without having to log	out and	in as that other user.

     If	Kerberos is in use, the	password for login (or for ``login/root'', if
     no	login is provided) is requested, and su	switches to that user and
     group ID after obtaining a	Kerberos ticket	granting access.  A shell is
     then executed, and	any additional shell arguments after the login name
     are passed	to the shell.  If Kerberos is not configured or	if there is a
     Kerberos error, su	falls back to local password authentication to vali-
     date the password for login.  If su is executed by	root, no password is
     requested and a shell with	the appropriate	user ID	is executed; no	addi-
     tional Kerberos tickets are obtained.

     By	default, the environment is unmodified with the	exception of LOGNAME,
     HOME, SHELL, and USER.  HOME and SHELL are	set to the target login's
     default values.  LOGNAME and USER are set to the target login, unless the
     target login has a	user ID	of 0 and the -l	flag was not specified,	in
     which case	it is unmodified.  The invoked shell is	the target login's.
     This is the traditional behavior of su.

     If	not using -m and the target login has a	user ID	of 0 then the PATH
     variable and umask	value (see umask(2)) are always	set according to the
     /etc/login.conf file (see login.conf(5)).

     The options are as	follows:

     -	     Same as the -l option (deprecated).

     -a	auth-type
	     Specify an	authentication type such as ``skey'', ``securid'', or

     -c	login-class
	     Specify a login class.  You may only override the default class
	     if	you're already root.

     -f	     If	the invoked shell is csh(1), this option prevents it from
	     reading the ``.cshrc'' file.

     -K	     Do	not attempt to use Kerberos to authenticate the	user.  This is
	     shorthand for ``su	-a passwd'', provided for backwards compati-

     -L	     Loop until	a correct username and password	combination is
	     entered, similar to login(1).  Note that in this mode target
	     login must	be specified explicitly, either	on the command line or
	     interactively.  Additionally, su will prompt for the password
	     even when invoked by root.

     -l	     Simulate a	full login.  The environment is	discarded except for
	     modified as above.	 LOGNAME and USER are set to the target	login.
	     PATH is set to the	value specified	by the ``path''	entry in
	     login.conf(5).  TERM is imported from your	current	environment.
	     The invoked shell is the target login's, and su will change
	     directory to the target login's home directory.

     -m	     Leave the environment unmodified.	The invoked shell is your
	     login shell, and no directory changes are made.  As a security
	     precaution, if the	target user's shell is a non-standard shell
	     (as defined by getusershell(3)) and the caller's real UID is non-
	     zero, su will fail.

     -s	login-shell
	     Specify the path to an alternate login shell.  You	may only over-
	     ride the shell if you're already root.  This option will override
	     the shell even if the -m option is	specified.

     The -l and	-m options are mutually	exclusive; the last one	specified
     overrides any previous ones.

     If	the optional shell arguments are provided on the command line, they
     are passed	to the login shell of the target login.	 This allows it	to
     pass arbitrary commands via the -c	option as understood by	most shells.
     Note that -c usually expects a single argument only; you have to quote it
     when passing multiple words.

     If	group 0	(normally ``wheel'') has users listed then only	those users
     can su to ``root''.  It is	not sufficient to change a user's /etc/passwd
     entry to add them to the ``wheel''	group; they must explicitly be listed
     in	/etc/group.  If	no one is in the ``wheel'' group, it is	ignored, and
     anyone who	knows the root password	is permitted to	su to ``root''.

     By	default	(unless	the prompt is reset by a startup file) the superuser
     prompt is set to ``#'' to remind one of its awesome power.

     HOME     Default home directory of	real user ID unless modified as	speci-
	      fied above.

     LOGNAME  The user ID is always the	effective ID (the target user ID)
	      after an su unless the user ID is	0 (root).

     PATH     Default search path of real user ID unless modified as specified

     TERM     Provides terminal	type which may be retained for the substituted
	      user ID.

     USER     Same as LOGNAME.

     Run the command ``makewhatis'' as user ``bin''.  You will be asked	for
     bin's password unless your	real UID is 0.

	   $ su	bin -c makewhatis

     Same as above, but	the target command consists of more than a single

	   $ su	bin -c 'makewhatis /usr/local/man'

     Same as above, but	the target command is run with the resource limits of
     the login class ``staff''.	 Note that the first -c	option applies to su
     while the second is an argument to	the shell.

	   $ su	-c staff bin -c	'makewhatis /usr/local/man'

     Pretend a login for user ``foo'':

	   $ su	-l foo

     Same as above, but	use S/Key for authentication:

	   $ su	-a skey	-l foo

     csh(1), kinit(1), login(1), sh(1),	skey(1), setusercontext(3), group(5),
     login.conf(5), passwd(5), environ(7), sudo(8)

     A su command appeared in Version 7	AT&T UNIX.

     The login name is not optional for	root if	there are shell	arguments.

FreeBSD	11.1		      September	21, 2017		  FreeBSD 11.1


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