[systemd-devel] A use case for staged startup

[Jeff Waugh]

On Sun, Feb 22, 2015 at 6:04 PM, Andrei Borzenkov <arvidjaar at gmail.com>
wrote:

> Do you really need to fully overlay root? I.e. is it possible to just
> (bind-)mount /etc, /var? /usr should be possible to retain read-only.
>

Once the upper layer of the overlayfs is JFFS2 (as intended), then it's
more interesting to have all of / overlayed.

> - and dutifully starts them all again once we're headed
> towards multi-user.target
> >
> > That's a *lot* of noise in the startup process!
>
> But does it actually work?
>

Yes, it does! It's so awesome that all of this machinery is built in, and
doesn't require reams of shell scripts.

So, it totally works, it just has performance warts because of my weird use
case. :-)


I believe that if you just overlay /etc with probably new
> default.target and run daemon-reload followed by isolate it /should/
> detect that some services are missing from new default.target and
> continue.


systemd can do all of that for me. The problem right now is that during the
initrd stage, it has access to *all* of the system services, so dutifully
starts them all up. Then isolates (kills them), switches root, and starts
them all up again.
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