newuidmap(1) — Linux manual page


NEWUIDMAP(1)                  User Commands                 NEWUIDMAP(1)

NAME         top

       newuidmap - set the uid mapping of a user namespace

SYNOPSIS         top

       newuidmap pid uid loweruid count [uid loweruid count [ ... ]]

DESCRIPTION         top

       The newuidmap sets /proc/[pid]/uid_map based on its command line
       arguments and the uids allowed. Subuid delegation can either be
       managed via /etc/subuid or through the configured NSS subid
       module. These options are mutually exclusive.

       Note that the root user is not exempted from the requirement for
       a valid /etc/subuid entry.

       After the pid argument, newuidmap expects sets of 3 integers:

           Beginning of the range of UIDs inside the user namespace.

           Beginning of the range of UIDs outside the user namespace.

           Length of the ranges (both inside and outside the user

       newuidmap verifies that the caller is the owner of the process
       indicated by pid and that for each of the above sets, each of the
       UIDs in the range [loweruid, loweruid+count) is allowed to the
       caller according to /etc/subuid before setting

       Note that newuidmap may be used only once for a given process.

       Instead of an integer process id, the first argument may be
       specified as fd:N, where the integer N is the file descriptor
       number for the calling process's opened file for /proc/[pid[. In
       this case, newuidmap will use openat(2) to open the uid_map file
       under that directory, avoiding a TOCTTOU in case the process
       exits and the pid is immediately reused.

OPTIONS         top

       There currently are no options to the newuidmap command.

FILES         top

           List of user's subordinate user IDs.

           Mapping of uids from one between user namespaces.

SEE ALSO         top

       login.defs(5), newusers(8), subuid(5), useradd(8), usermod(8),

COLOPHON         top

       This page is part of the shadow-utils (utilities for managing
       accounts and shadow password files) project.  Information about
       the project can be found at 
       ⟨⟩.  If you have a bug
       report for this manual page, send it to  This page was obtained
       from the project's upstream Git repository
       ⟨⟩ on 2023-12-22.  (At that
       time, the date of the most recent commit that was found in the
       repository was 2023-12-15.)  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

shadow-utils 4.11.1            12/22/2023                   NEWUIDMAP(1)

Pages that refer to this page: getsubids(1)unshare(1)mount_setattr(2)subgid(5)subuid(5)user_namespaces(7)