It's debatable whether root should be a non-interactive user. For example, nixops ssh logs in as root by default.

By "non-interactive" I meant "not a human doing general purpose stuff". I'm not sure if having ssh-agent running as root has its uses but keybase/kbfs definitely shouldn't be running.

In any case, this PR doesn't change anything about the definition of root - it only disables the 3 mentioned user units for root.

I'd say this should be configurable.

There are even more user services where this change would be useful. For instance, btsync, gpg-agent and pulseaudio. Maybe we should give each user service an extra option to set for which users the service is started. On the other hand we do have ConditionUser which can be overridden in any NixOS config but this is an implementation detail.

For most user services I agree that it doesn't make much sense to run them as root or other non-interactive users. I think this should be the default for all our user services.

@edolstra - do you still have reservations about this PR?

@rvolosatovs you said:

I'd say this should be configurable

You're saying that we should be able to define per service if it should run for root as well or a global switch of some kind? Can you share some details on your specific use case?

What I had in mind was having something like runAsRoot boolean option, or, even better, similar to what @fpletz proposed having something like a users option, where you could define the users to run the service for, or, other way round, having a services option in user definition, where the services, that should run would be cofigured.
Another idea was that maybe it could be abstracted somehow... like being able to specify non-interactive users, for whom "interactive" services would not get started.

By the way, shouldn't all systemd.user.services only run for non-root users anyway?

having something like a users option, where you could define the users to run the service for

That makes sense, but is really just the mechanics of it. What would be the use case for running syncthing or keybase as root?

By the way, shouldn't all systemd.user.services only run for non-root users anyway?

That's what I would say although services wantedBy = [ "graphical-session.target" ]; do not require handling as that target should never be started by root in the first place.

Any update on this pull request?

This is safe to merge - the 3 mentioned services should not run as root.