My Experiences with ninit [Part 1]
This post is a collection of notes of the process I went through to take out
systemd for ninit. Pardon for the scarcity, but I'll revisit this with better descriptions.
What IS ninit?
Preparation
- Install procps-ng-nosystemd
- Temporary symlink to systemd-udevd
- Install ninit
- Set up service directories. You can find a rough copy (though not perfectly
synced) copy of my /etc/ninit dir here - Reboot
Post-install
eudev{,-systemdcompat}
- manually build eudev and eudev-systemdcompat
- Remove the symlink from preparations in systemd
- intall eudev and eudev-systemdcompat
- Reboot to test things
nsvc -o {halt,reboot} vs ninit-shutdown -{o,r}
I recommend ninit-shutdown -{o,r} if you don't want to manually handle turning
services off before doing shutdown preparations in the halt service. ninit-shutdown
also assumes quite a few things about how a system should be cleaned up, so if you
want more control, you're going to have to fiddle with the halt service to shutdown
the services you want in the correct order before halting.
Optional: pretty messages for every section started
[Edit]: Forgot to fill this section out. Basically, all that's needed for this is a
setup file that echos out a simple message.
Depends aren't really "depends" - more like "start before"
Title says it all. ninit won't actually check if the services that a service depends
on have finished executing with success or are running. Just ran some tests in my
test box. Didn't seem to restart dbus even when I had two things dependent on it.
However, statement about whether something finishes with success is still valid.
Some ways to work around this include:
- Specify the order daemons are started in like /etc/rc.conf, except with
/etc/ninit/daemon/depends: Simple enough work around. Everything's also started
in parallel like this. - Patch ninit
to include a separate file for services (opt) that specifies trueto do something about the return
deps that're only run once OR modifies the depends of certain services once it's
done running: Too complex, but could be done.
code for one-run services. -
Use setup, rsetup, or sys-rsetup to do the dependency checking for shared
dependencies: One of the things that the ninit docs don't tell you is that using
nsvc as a synced or waited service is NOT a good idea (nor as a services that's in
depends either). I really wouldn't recommend this because this makes things complex.
Only applicable for one-run services.
Thoughts
ninit's good enough if you've got a static configuration that doesn't have too many depends
that can be easily managed and that don't require too many static initializations. It also
doesn't seem to keep track of exit codes for error spotting (since a service could fail, but
report back as finished. This is especially bad in mounting cases unless you force the mount
to be verbose or write a wrapper to do something on that error). However, it'll happily report
if something failed to run if it was a continuous service. There also isn't much documentation
on what the nsvc -L output indicates. I'll try to document these later.
For true depends for one-time initializations, I'd recommend something else (at least until I can
figure out how to patch the run helper in ninit to work around this). I'm thinking of maybe also
trying out busybox init+(monit or perp), initng, OpenRC, or initscripts-fork. Currently, I'm
interested in trying monit (even though this'd probably be a little too big for my own needs) since
it does this dependency checking on its own and provides some additional security features that can
be coded (eg: stop running a compromised service). The only thing that scares me about it is that it
prefers pid files instead of being a direct parent of the process (as evidenced by with matching|pidfile
when asking what to check for a pid). I just need to figure out which init system to run it from before
I start trying it out.
