The option is disabled by default so that previously existing installations
aren't affected.
If you'd like to migrate to the fixed numeric id for Apache, set "fixUidAndGid
= true", edit the file "/etc/groups" and replace the old GID value with 54.
(NixOS can't do that for you because it refuses to change a GID that identifies
the primary group of a user.) Then run
find / -xdev -uid $oldUID -exec chown 54 {} +
find / -xdev -gid $oldGID -exec chgrp 54 {} +
to update ownership of all files that are supposed to be owned by Apache.
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