NAME

       newgidmap - set the gid mapping of a user namespace

SYNOPSIS

       newgidmap pid gid lowergid count [gid lowergid count [ ... ]]

DESCRIPTION

       The newgidmap sets /proc/[pid]/gid_map based on its command line arguments and the gids
       allowed. Subgid delegation can either be managed via /etc/subgid or through the configured
       NSS subid module. These options are mutually exclusive.

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

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

       gid
           Beginning of the range of GIDs inside the user namespace.

       lowergid
           Beginning of the range of GIDs outside the user namespace.

       count
           Length of the ranges (both inside and outside the user namespace).

       newgidmap verifies that the caller is the owner of the process indicated by pid and that
       for each of the above sets, each of the GIDs in the range [lowergid, lowergid+count) is
       allowed to the caller according to /etc/subgid before setting /proc/[pid]/gid_map.

       Note that newgidmap 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 descriptor
       for the directory /proc/[pid]. In this case, newgidmap will use openat(2) to open the
       gid_map file under that directory, avoiding a TOCTTOU in case the process exits and the
       pid is immediately reused.

OPTIONS

       There currently are no options to the newgidmap command.

FILES

       /etc/subgid
           List of user's subordinate group IDs.

       /proc/[pid]/gid_map
           Mapping of gids from one between user namespaces.

SEE ALSO

       login.defs(5), newusers(8), subgid(5), useradd(8), userdel(8), usermod(8).