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runuser

run a command with substitute user and group ID

runuser [options] -u user command [argument...]

runuser [options] [-] [user [argument...]]

runuser allows to run commands with a substitute user and group ID. If the option -u is not given, it falls back to su-compatible semantics and a shell is executed. The difference between the commands runuser and su is that runuser does not ask for a password (because it may be executed by the root user only) and it uses a different PAM configuration. The command runuser does not have to be installed with suid permissions.

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

For backward compatibility, runuser 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). This version of runuser uses PAM for session management.

Pass command to the shell with the -c option.
Pass -f to the shell, which may or may not be useful depending on the shell.
The primary group to be used. This option is allowed for the root user only.
A supplemental group to be used. This option is allowed for the root user only.
-, -l, --login
Start the shell as a login shell with an environment similar to a real login:
clears all the environment variables except for TERM
initializes the environment variables HOME, SHELL, USER, LOGNAME, PATH
changes to the target user's home directory
sets argv[0] of the shell to '-' in order to make the shell a login shell
Preserve the entire environment, i.e. it does not set HOME, SHELL, USER nor LOGNAME. The option is ignored if the option --login is specified.
Run the specified shell instead of the default. The shell to run is selected according to the following rules, in order:
the shell specified with --shell
the shell specified in the environment variable SHELL if the --preserve-environment option is used
the shell listed in the passwd entry of the target user
/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.
Same as -c , but do not create a new session. (Discouraged.)
Display version information and exit.
Display help text and exit.

runuser reads the /etc/default/runuser and /etc/login.defs configuration files. The following configuration items are relevant for runuser:

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 runuser initializes PATH.

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

Exit status generated by runuser itself:

1
Generic error before executing the requested command
126
The requested command could not be executed
127
The requested command was not found

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

pam(8), shells(5), login.defs(5), su(1)

This runuser command was derived from coreutils' su, which was based on an implementation by David MacKenzie, and the Fedora runuser command by Dan Walsh.

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