Some software decides based on uid/gid whether a user is a system or
normal (human) user, with different behaviour for those flavors (example
journald [2]).
So adding logic to create system-users is necessary, we take the now
common ranges from [1].
This extends the mkusers script to allow -2 for uid/gid, this argument
will take an identifier from the user range. All identifiers used up to
now should have been from the system range, so -1 is now interpreted as
a system user/group.
Note that after this commit, all the UIDs and GIDs that are created
automatically (with -1) will change. That means if there is peristent
data on an existing system that was created by such an automatic user,
it will suddenly belong to a different user. However, this could already
happen before: if a USERS line is added to a package, then other UIDs
may change as well.
Add system/user ranges as variables, and the argument for user/system
uid variable as well. Thus some magic constants could be removed, some
further occurences of -1 were replaced with equivalent logic. For
consistency, the existing MIN/MAX_UID/GID variables are renamed to
FIRST/LAST_USER_UID/GID.
Update the documentation with the new automatic ranges.
[1] - https://systemd.io/UIDS-GIDS/
[2] - https://www.freedesktop.org/software/systemd/man/journald.conf.html
Signed-off-by: Norbert Lange <nolange79@gmail.com>
[Arnout: use -1 for system users; refactor the changes a bit]
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
41ea61d59c