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April, 26th. 2006:
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NEWGIDMAP
Section: User Commands (1) Updated: 02/01/2026 Index
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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).
Index
- NAME
-
- SYNOPSIS
-
- DESCRIPTION
-
- OPTIONS
-
- FILES
-
- SEE ALSO
-
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