lxc-usernsexec(1) — Linux manual page


LXC-USERNSEXEC(1)                                          LXC-USERNSEXEC(1)

NAME         top

       lxc-usernsexec - Run a task as root in a new user namespace.

SYNOPSIS         top

       lxc-usernsexec [ -m uid-map ]  -- command

DESCRIPTION         top

       lxc-usernsexec can be used to run a task as root in a new user

OPTIONS         top

       -m uid-map
              The uid map to use in the user namespace. Each map consists of
              four colon-separate values. First a character 'u', 'g' or 'b'
              to specify whether this map pertains to user ids, group ids,
              or both; next the first userid in the user namespace; next the
              first userid as seen on the host; and finally the number of
              ids to be mapped.

              More than one map can be specified. If no map is specified,
              then by default the full uid and gid ranges granted by
              /etc/subuid and /etc/subgid will be mapped to the uids and
              gids starting at 0 in the container.

              Note that lxc-usernsexec always tries to setuid and setgid to
              0 in the namespace. Therefore uid 0 in the namespace must be

EXAMPLES         top

       To spawn a shell with the full allotted subuids mapped into the
       container, use


       To run a different shell than /bin/sh, use

              lxc-usernsexec -- /bin/bash

       If your user id is 1000, root in a container is mapped to 190000, and
       you wish to chown a file you own to root in the container, you can

              lxc-usernsexec -m b:0:1000:1 -m b:1:190000:1 -- /bin/chown 1:1 $file

       This maps your userid to root in the user namespace, and 190000 to
       uid 1.  Since root in the user namespace is privileged over all
       userids mapped into the namespace, you are allowed to change the file
       ownership, which you could not do on the host using a simple chown.

SEE ALSO         top

       lxc(7), lxc-create(1), lxc-copy(1), lxc-destroy(1), lxc-start(1),
       lxc-stop(1), lxc-execute(1), lxc-console(1), lxc-monitor(1),
       lxc-wait(1), lxc-cgroup(1), lxc-ls(1), lxc-info(1), lxc-freeze(1),
       lxc-unfreeze(1), lxc-attach(1), lxc.conf(5)

AUTHOR         top

       Serge Hallyn <serge.hallyn@ubuntu.com>

COLOPHON         top

       This page is part of the lxc (Linux containers) project.  Information
       about the project can be found at ⟨http://linuxcontainers.org/⟩.  If
       you have a bug report for this manual page, send it to
       lxc-devel@lists.linuxcontainers.org.  This page was obtained from the
       project's upstream Git repository ⟨git://github.com/lxc/lxc⟩ on
       2020-08-13.  (At that time, the date of the most recent commit that
       was found in the repository was 2020-08-12.)  If you discover any
       rendering problems in this HTML version of the page, or you believe
       there is a better or more up-to-date source for the page, or you have
       corrections or improvements to the information in this COLOPHON
       (which is not part of the original manual page), send a mail to

                                 2020-08-13                LXC-USERNSEXEC(1)