NEWGIDMAP(1) User Commands NEWGIDMAP(1)
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).
shadow-utils 4.17.4 04/19/2025 NEWGIDMAP(1)
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