coreos-boot-edit: add triggering condition on coreos-copy-firstboot-network.stamp

[jlebon]

That way we completely avoid mounting /boot rw if we don't need to.
Also clarify comment about the boot dependency. Additional roles for
this service ideally would follow the same pattern.

Minor follow-up to #743.

[jlebon]

Not tested yet.

[travier]

LGTM

[kelvinfan001]

LGTM!

[jlebon]

Once we merge coreos-inject-rootmap.service into this, then I think the motivation for using the triggering model proposed here drops a lot because right now we always inject at least root=... rw on first boot, so the service will just always kick in. (It's conditional on root= not being present, but that karg being present on firstboot is a bit of a snowflake -- mostly for setting up multipath at install-time).

So closing this one. (And accordingly, we can indeed drop the stamp file as discussed in #743.)

[kelvinfan001]

Just to be sure, would this mean we get rid of ConditionKernelCommandLine=!root too (since it's rare that it's not satisfied)? Or keep the stamp file and have

ConditionKernelCommandLine=|!root
ConditionPathExists=|/run/coreos-copy-firstboot-network.stamp

[jlebon]

I was arguing for dropping the triggering conditions entirely and just having the unit always run to be consistent, even if in some rare situations it might not have been necessary.

We'd still make the call to rdcore rootmap itself in the script conditional on root= not being present in /proc/cmdline though.

[kelvinfan001]

We'd still make the call to rdcore rootmap itself in the script conditional on root= not being present in /proc/cmdline though.

Ahh, got it. 👍