`usermod` flag to write `subuid` and `subgid` entries by UID rather than username

[jcpunk]

From the subuid manpage:

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.

It would be helpful if there was something I could set in /etc/login.defs or with usermod to write out subids with their UID instead of the username.

I suspect this would be of value to useradd as well.

[alejandro-colomar]

From the subuid manpage:

Please use proper manual page references: subuid(5). Otherwise, it might be unclear to which page you refer to.

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.

It would be helpful if there was something I could set in /etc/login.defs or with usermod to write out subids with their UID instead of the username.

I suspect this would be of value to useradd as well.

Cc: @richardweinberger , @ikerexxe , @hallyn

[hallyn]

No objection. login.defs probably makes the most sense, since having just one of the entries use UID isn't going to help if it's performance you care about.