SU(1) General Commands Manual SU(1)NAME
su - substitute user id temporarily
su [ -f ] [ - ] [ userid ]
Su demands the password of the specified userid, and if it is given, changes to that userid and invokes the Shell sh(1) or csh(1) without
changing the current directory. The user environment is unchanged except for HOME and SHELL, which are taken from the password file for
the user being substituted (see environ(7)). The new user ID stays in force until the Shell exits.
If no userid is specified, ``root'' is assumed. Only users in the ``wheel'' group (group 0) can su to ``root'', even with the root pass-
word. To remind the super-user of his responsibilities, the Shell substitutes `#' for its usual prompt.
The -f option prevents csh(1) from executing the .cshrc file; thus making su start up faster.
The - option simulates a full login.
SEE ALSO sh(1), csh(1)3rd Berkeley Distribution May 5, 1986 SU(1)
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SU(1) BSD General Commands Manual SU(1)NAME
su -- substitute user identity
su [-] [-flm] [login [args]]
The su utility requests appropriate user credentials via PAM and switches to that user ID (the default user is the superuser). A shell is
PAM is used to set the policy su(1) will use. In particular, by default only users in the ``admin'' or ``wheel'' groups can switch to UID 0
(``root''). This group requirement may be changed by modifying the ``pam_group'' section of /etc/pam.d/su. See pam_group(8) for details on
how to modify this setting.
By default, the environment is unmodified with the exception of USER, HOME, and SHELL. HOME and SHELL are set to the target login's default
values. USER is set to the target login, unless the target login has a user ID of 0, in which case it is unmodified. The invoked shell is
the one belonging to the target login. This is the traditional behavior of su.
The options are as follows:
-f If the invoked shell is csh(1), this option prevents it from reading the ``.cshrc'' file.
-l Simulate a full login. The environment is discarded except for HOME, SHELL, PATH, TERM, and USER. HOME and SHELL are modified as
above. USER is set to the target login. PATH is set to ``/bin:/usr/bin''. 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.
- (no letter) The same as -l.
-m Leave the environment unmodified. The invoked shell is your login shell, and no directory changes are made. As a security precau-
tion, 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
The -l (or -) and -m options are mutually exclusive; the last one specified overrides any previous ones.
If the optional args are provided on the command line, they are passed to the login shell of the target login. Note that all command line
arguments before the target login name are processed by su itself, everything after the target login name gets passed to the login shell.
By default (unless the prompt is reset by a startup file) the super-user prompt is set to ``#'' to remind one of its awesome power.
Environment variables used by su:
HOME Default home directory of real user ID unless modified as specified above.
PATH Default search path of real user ID unless modified as specified above.
TERM Provides terminal type which may be retained for the substituted user ID.
USER The user ID is always the effective ID (the target user ID) after an su unless the user ID is 0 (root).
/etc/pam.d/su PAM configuration for su.
su man -c catman
Runs the command catman as user man. You will be asked for man's password unless your real UID is 0.
su man -c 'catman /usr/share/man /usr/local/man'
Same as above, but the target command consists of more than a single word and hence is quoted for use with the -c option being passed
to the shell. (Most shells expect the argument to -c to be a single word).
su -l foo
Simulate a login for user foo.
su - foo
Same as above.
su - Simulate a login for root.
SEE ALSO csh(1), sh(1), group(5), passwd(5), environ(7), pam_group(8)HISTORY
A su command appeared in Version 1 AT&T UNIX.
BSD September 13, 2006 BSD