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

       o   login name

       o   numerical subordinate user ID

       o   numerical subordinate user ID count

       This file specifies the user IDs to be that each user may use with the
       newuidmap command that ordinary users can use to configure uid mapping
       in a user namespace.

       Multiple ranges may be specified per user ID.

           Per user subordinate user IDs.

           Backup file for /etc/subuid.

       subgid(5), login.defs(5), newuidmap(1), newgidmap(1), usermod(8),

shadow-utils              05/16/2017                         SUBUID(5)
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