subgid(5) [linux man page]

SUBGID(5)                                                  File Formats and Conversions                                                  SUBGID(5)

NAME

       subgid - the subordinate gid file

DESCRIPTION

       Each line in /etc/subgid contains a user name and a range of subordinate group ids that user is allowed to use. This is specified with
       three fields delimited by colons (":"). These fields are:

       o   login name or UID

       o   numerical subordinate group ID

       o   numerical subordinate group ID count

       This file specifies the group IDs that ordinary users can use, with the newgidmap command, to configure gid mapping in a user namespace.

       Multiple ranges may be specified per user.

       When large number of entries (10000-100000 or more) are defined in /etc/subgid, parsing performance penalty will become noticeable. In this
       case it is recommended to use UIDs instead of login names. Benchmarks have shown speed-ups up to 20x.

FILES

       /etc/subgid
           Per user subordinate group IDs.

       /etc/subgid-
           Backup file for /etc/subgid.

SEE ALSO

       login.defs(5), newgidmap(1), newuidmap(1), newusers(8), subuid(5), useradd(8), userdel(8), usermod(8), user_namespaces(7).

shadow-utils 4.5                                                    01/25/2018                                                           SUBGID(5)