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 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 set-user-ID permissions.

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

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.

Note that runuser in all cases use PAM (pam_getenvlist()) to do final environment modification. The command line options like --login or --preserve-environment affect environment before it's modified by PAM.

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 supplemental 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 unspecified.

-, -l, --login
    Start the shell as a login shell with an environment similar to a real login:

    o   clears all the environment variables except for TERM and variables specified by --whitelist-environment

    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

-P, --pty
    Create pseudo-terminal for the session. The independent terminal provides better security as user does not share terminal with the original session. This allow to avoid TIOCSTI ioctl terminal injection and another security attacks against terminal file descriptors. The all session is also possible to move to background (e.g., "runuser --pty -u username -- command &"). If the pseudo-terminal is enabled then runuser command works as a proxy between the sessions (copy stdin and stdout).

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

-m, -p, --preserve-environment
    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.

-s, --shell=shell
    Run 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.

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

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

-V, --version
    Display version information and exit.

-h, --help
    Display help text 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 --login command line option and PAM system setting (e.g. pam_env).

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

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

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.

AVAILABILITY
The runuser command is part of the util-linux package and is available from Linux Kernel Archive (https://www.kernel.org/pub/linux/utils/util-linux/).