Manual: runuser

RUNUSER(1)						User Commands						  RUNUSER(1)

NAME
       runuser - run a command with substitute user and group ID

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

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

DESCRIPTION
       runuser can be used to run commands with a substitute user and group ID. If the option -u is not given, runuser 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 set-user-ID permissions.

       If the PAM session is not required, then the recommended solution is to use the setpriv(1) command.

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

       For backward compatibility, runuser defaults to not changing the current directory and to setting only 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.

       Note that runuser in all cases use PAM (pam_getenvlist()) to do the final environment modification. Command-line
       options such as --login and --preserve-environment affect the environment before it is modified by PAM.

       Since version 2.38 runuser resets process resource limits RLIMIT_NICE, RLIMIT_RTPRIO, RLIMIT_FSIZE, RLIMIT_AS and
       RLIMIT_NOFILE.

OPTIONS
       -c, --command=command
	   Pass command to the shell with the -c option.

       -f, --fast
	   Pass -f to the shell, which may or may not be useful, depending on the shell.

       -g, --group=group
	   The primary group to be used. This option is allowed for the root user only.

       -G, --supp-group=group
	   Specify a supplementary group. This option is available to the root user only. The first specified supplementary
	   group is also used as a primary group if the option --group is not specified.

       -, -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 and variables specified by --whitelist-environment

	   •   initializes the environment variables HOME, SHELL, USER, LOGNAME, and 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

       -m, -p, --preserve-environment
	   Preserve the entire environment, i.e., do not set HOME, SHELL, USER or LOGNAME. The option is ignored if the
	   option --login is specified.

       -P, --pty
	   Create a pseudo-terminal for the session. The independent terminal provides better security as the user does not
	   share a terminal with the original session. This can be used to avoid TIOCSTI ioctl terminal injection and other
	   security attacks against terminal file descriptors. The entire session can also be moved to the background (e.g.,
	   runuser --pty -u user -- command &). If the pseudo-terminal is enabled, then runuser works as a proxy between the
	   sessions (sync stdin and stdout).

	   This feature is mostly designed for interactive sessions. If the standard input is not a terminal, but for
	   example a pipe (e.g., echo "date" | runuser --pty -u user), then the ECHO flag for the pseudo-terminal is
	   disabled to avoid messy output.

       -s, --shell=shell
	   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), then the --shell option and the
	       SHELL environment variables are ignored unless the calling user is root.

       --session-command=command
	   Same as -c, but do not create a new session. (Discouraged.)

       -T, --no-pty
	   Do not create a pseudo-terminal, opposite of --pty and -P. Note that running without a pseudo-terminal opens the
	   security risk of privilege escalation through TIOCSTI/TIOCLINUX ioctl command injection.

       -u, --user=user
	   Run command with the effective user ID and group ID of the user name user.

       -w, --whitelist-environment=list
	   Don’t reset the environment variables specified in the comma-separated list when clearing the environment for
	   --login. The whitelist is ignored for the environment variables HOME, SHELL, USER, LOGNAME, and PATH.

       -h, --help
	   Display help text and exit.

       -V, --version
	   Display version and exit.

CONFIG FILES
       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. ENV_SUPATH takes precedence. 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.

       The environment variable PATH may be different on systems where /bin and /sbin are merged into /usr; this variable is
       also affected by the --login command-line option and the PAM system setting (e.g., pam_env(8)).

EXIT STATUS
       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

FILES
       /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

HISTORY
       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.

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

REPORTING BUGS
       For bug reports, use the issue tracker .

AVAILABILITY
       The runuser command is part of the util-linux package which can be downloaded from Linux Kernel Archive
       .

util-linux 2.41.3					 2025-12-15						  RUNUSER(1)