Ubuntu Manpages

subgid

the subordinate gid file

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:

•login name or UID

•numerical subordinate group ID

•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.

/etc/subgid

Per user subordinate group IDs.

/etc/subgid-

Backup file for /etc/subgid.

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