runuser

Examples (TL;DR)

• Run command as a different user: runuser user -c 'command'
• Run command as a different user and group: runuser user -g group -c 'command'
• Start a login shell as a specific user: runuser user -l
• Specify a shell for running instead of the default shell (also works for login): runuser user -s /bin/sh
• Preserve the entire environment of root (only if --login is not specified): runuser user --preserve-environment -c 'command'

tldr.sh

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.

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:

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

-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:

• 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.

--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.

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.

Referenced By

credentials(7), setpriv(1), su(1).