[systemd-devel] minimal required units

Aaron_Wright at selinc.com Aaron_Wright at selinc.com
Fri Mar 13 08:31:44 PDT 2015


...snip...

> > If I include at least all of the units leading up to basic.target, 
would 
> > that cover the units required by systemd?
> 
> systemd does not really require anything. Really. *You* (or your
> system) require something to be started during boot and only you know
> what should be started. You can use single service that calls /etc/rc
> as starting point and split it up step by step.
> 
> Units shipped with systemd help to organize system startup in logical
> steps and provide common hooks to plug your own extensions into.
> Removing common hooks won't buy you anything but will make system less
> flexible and harder to troubleshoot.

Yes, I think I'm changing my point of view a bit. I'm coming from a 
busybox inittab world, where I only included just what I needed, and 
anything extra was doing something bad. You and Alison Chaiken have 
explained the systemd philosophy to me, so that I think I understand it 
much more. Thanks for taking the time.

In order to get the proper configuration I want, I'm doing my own 
packaging for systemd. After the build, I cherry pick what I want 
installed on the box. It sounds like I need to stop cherry picking so 
much, and just install whole folders; such as:

usr/lib/systemd/system/
etc/systemd/

And even though, that'll get me lots of units I'll never use, it'll be the 
safest bet for a smooth running systemd. Correct?

...snip...

> > I'm concerned because I left out local-fs.target to begin with, as I 
don't 
> > need systemd to mount anything, but that seemed to cause systemd to 
> > unmount everything other than / and the kernel file systems.
> 
> Sorry, that does not fit. Either you "do not need to mount anything" or
> "systemd unmount everything". What was there to unmount if you did not
> mount anything in the first place? 

I mount / and /var in initrd, and then switch to the new root. systemd 
then proceeded to unmount /var, but it didn't really tell me why. After I 
included the local-fs.target on the box, that strange behavior stopped, 
and /var remains mounted. I can't really explain that one.

...snip...
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