SUBUID(5)                 (02/07/2020)                  SUBUID(5)

     NAME
          subuid - the subordinate uid file

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

          +o   login name or UID

          +o   numerical subordinate user ID

          +o   numerical subordinate user ID count

          This file specifies the user IDs that ordinary users can
          use, with the newuidmap command, to configure uid 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/subuid, 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/subuid
              Per user subordinate user IDs.

          /etc/subuid-
              Backup file for /etc/subuid.

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

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