Add storage: volatile: true

[cgwalters]

Let's support something like:

storage:
  volatile: true

This would have an effect like passing the systemd.volatile kernel command line argument; see also ostreedev/ostree#856

Basically we have this logic today in our "Live" path; this would generalize it so it could easily be used for cloud instances too.

In particuar, I can see this being used by openshift-install for the bootstrap node. Then we could pretty easily get rid of the bootstrap node requirement and have it re-Ignition itself into a control plane node. This would greatly help the baremetal provisioning flow which does weird things with running bootstrap in a VM.

[cgwalters]

The implementation of this could just be writing out /run/ostree-live, and then we teach fedora-coreos-config how to handle that generically. Or we could try to get agreement with systemd upstream to have /run/systemd.volatile or something that other Ignition users could also key off of.

[cgwalters]

@bgilbert raised in chat the issue of how this interacts with rebooting. I think the basic answer here is - we wouldn't remove the /boot/ignition.firstboot flag, the same way we don't in the liveOS path. So every boot would run Ignition.

[darkmuggle]

The implementation of this could just be writing out /run/ostree-live, and then we teach fedora-coreos-config how to handle that generically. Or we could try to get an agreement with systemd upstream to have /run/systemd.volatile or something that other Ignition users could also key off of.

I'm not sure that we can use systemd.volatile=yes, since it only remounts /sysroot. I think that the caused by systemd-tmpfiles but not sure.

bash-5.0# pwd
/sysroot/ostree/deploy/fedora-coreos/var/home
bash-5.0# find .
.
./core
./core/.bash_logout
./core/.bash_profile
./core/.bashrc
bash-5.0# find /home
/home

[cgwalters]

I'm not sure that we can use systemd.volatile=yes

Agreed; a lot of the upstream systemd stuff is oriented towards mounting /usr as a filesystem, kind of glossing over how / is managed. OSTree is much stricter with its /etc and /var are the only writable bits model.

[bgilbert]

This is a very OS-specific option, which mitigates against the feature, and it seems like this functionality could be implemented with kargs support (#1051) and/or writing a normal file. Closing for now.

[cgwalters]

Moved this to coreos/fedora-coreos-tracker#674