Re:Systemd, ten years later: a historical and technical retr...
by throw0101a on Friday May 08, 2020 @01:26PM
(#23117216)
The weblog post has an user called '0day', i.e., "zero day". This breaks systemd as outlined in the post. This is a WONTFIX per the systemd folks.
Now assuming I have a user called 1000 with UID 2000, and a user called 2000 with UID 1000.
Now what do you think is gonna happen if multiple POSIX-compliant tools call each other?
This is clearly broken, and the reason why BSDs don’t actually implement POSIX cleanly, instead allowing all their tools to take unambiguous identifiers on the CLI, with the # prefix to mark a UID, and have all their tools call all their children with this format.
The POSIX standard is clearly suboptimal here, and the set of valid usernames, and the set of valid UIDs should never have been allowed to overlap.