Before: `users.users.user1.group = "group-not-defined-anywhere-else"`
would result in user1 having the primary group `nogroup`, assigned at
activation time and only with a (easy to miss) warning from the
activation script. This behaviour is a security issue becase no files
should be owned by `nogroup` and it allows for unrelated users (and
services) to accidentally have access to files they shouldn't have.
After: The configuration above results in this eval error:
- The following users have a primary group that is undefined: user1
Hint: Add this to your NixOS config:
users.groups.group-not-defined-anywhere-else = {};
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