su(1) [mojave man page]
SU(1) BSD General Commands Manual SU(1) NAME
su -- substitute user identity SYNOPSIS
su [-] [-flm] [login [args]] DESCRIPTION
The su utility requests appropriate user credentials via PAM and switches to that user ID (the default user is the superuser). A shell is then executed. 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 will fail. 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
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). FILES
/etc/pam.d/su PAM configuration for su. EXAMPLES
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
Check Out this Related Man Page
SU(1) User Commands SU(1) NAME
su - run a command with substitute user and group ID SYNOPSIS
su [options...] [-] [user [args...]] DESCRIPTION
su allows to run commands with 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 directory 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 it's 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 e.g. support of a wheel group have to be configured via PAM. OPTIONS
-c command, --command=command Pass command to the shell with the -c option. --session-command=command 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 allowed for root user only -G, --supp-group=group specify a supplemental group, this option is allowed for 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 for TERM o initializes the environment variables HOME, SHELL, USER, LOGNAME, PATH 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, ie does not set HOME, SHELL, USER nor LOGNAME. The option is ignored if the option --login is specified. -s SHELL, --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 user 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 variables are ignored unless the calling user is root. --help Display help text and exit. --version Display version information and exit. CONFIG FILES
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 specified su initializes PATH. EXIT STATUS
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 FILES
/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 SEE ALSO
runuser(8), pam(8), shells(5), login.defs(5) AUTHOR
Derived from coreutils' su which was based on an implementation from David MacKenzie. AVAILABILITY
The su command is part of the util-linux package and is available from Linux Kernel Archive <ftp://ftp.kernel.org/pub/linux/utils/util- linux/>. util-linux June 2012 SU(1)