[Nix-dev] Will there be a systemd replacement at any time inthefuture?

[Mathijs Kwik]

I also don't see these issues with journald (on non-SSD systems).

I would like to add I absolutely love systemd, as it provides proper
dependency management, helping immensely for more dynamic setups where
hardware changes should trigger services reconfiguration, or for
changing services/vpn/routing based on wifi access point and more.
It's really nice that - when configured well - things just work, no
matter if you're booting, restarting some service or switching to a new
configuration. No more subtle timing errors or things that need manual
restarts in edgy situations. Systemd's "state manager" is extremely
capable. And extremely fast compared to oldschool linear scripts.

Also - althoughh nix abstracts over it - configuration through unit
files is declarative and clean. Unifying things like daemonizing,
run-as-other-user, run-in-chroot, apply capabilities and logging is
brilliant compared to ambiguous scripting hacks.

I really feel systemd is a perfect match for nixos. Nix manages state on
disk, systemd manages runtime state. Both try to do this as
deterministically as possible, though a declarative configuration.

Sure there might be some operational bugs, but I would suggest turning
them into issues, tracking them down and taking things up with
upstream as they are probably not all that huge. The overall design
seems very well thought-out and clean. 

If we ever want to move to some other init system, I think this will
be easier than the upstart->systemd move. That move was mostly
complicated by the fact that upstart just didn't have most config
settings and abstractions, so stuff for run-as-user and daemonization
logic was put into a bash script. That had to be extracted into
attributes. If we move to something else, we now have nicely abstracted
configurations for most services (although named systemd.services.*
instead of something more generic), so exporting config files for
anything (even upstart) based on these attributes is probably gonna be
easy, making a "port" way simpler than before.

Just my 2 cents :)
Mathijs