Man1 - newgidmap.1

newgidmap - set the gid mapping of a user namespace

newgidmap pid gid lowergid count [/gid/ lowergid count [ … ]]

The newgidmap sets proc[pid]/gid_map based on its command line arguments and the gids allowed in /etc/subgid. Note that the root user 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.

There currently are no options to the newgidmap command.

/etc/subgid

List of users subordinate group IDs.

proc[pid]/gid_map

Mapping of gids from one between user namespaces.

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