x SuSE Linux 13.1-RELEASE x
x SuSE Linux 13.1-RELEASEx
SU(1) User Commands SU(1)
NAME
su - run a command with substitute user and group ID
SYNOPSIS
su [options] [-] [user [argument...]]
DESCRIPTION
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 for a wheel group, have to be configured via
PAM.
OPTIONS
-c, --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 available to the root
user only.
-G, --supp-group=group
Specify a supplemental group. This option is available to the
root user only.
-, -l, --login
Starts the shell as a login shell with an environment similar to
a real login:
o clears all the environment variables except TERM
o initializes the environment variables HOME, SHELL,
USER, LOGNAME, and 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 entire 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
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 vari-
ables are ignored unless the calling user is root.
--help Display help text and exit.
--version
Display version information and exit.
SIGNALS
Upon receiving either SIGINT, SIGQUIT or SIGTERM, su terminates its
child and afterwards terminates itself with the received signal.
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 an authentication failure. The 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.
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 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
NOTES
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 the last-
log file as well. For example by:
session required pam_lastlog.so nowtmp
SEE ALSO
runuser(8), pam(8), shells(5), login.defs(5)
AUTHOR
Derived from coreutils' su which was based on an implementation by
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 October 2013 SU(1)
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