Enable snaps to run before SSH comes up in classic boot process

[Dan Watkins]

A common pattern for daemons that are provided by cloud vendors (e.g. GCE, Windows Azure) is that they need to block some part of the boot to do configuration.

Most often, they need to run after networking is up but before SSH is up, to communicate with their metadata services to provision SSH configuration, so it would be good to solve that particular use case.

[Dan Watkins (oddbloke)]

I could see this being solved in a couple of ways: either provide a specific way of specifying that we want to run before SSH is up, or provide a generic way of interleaving services in to the regular systemd boot process using unit names.

[Jamie Bennett (jamiebennett)]

Is this something that is a one-shot i.e. just on first boot?

Also, as this is in a classic environment and not Ubuntu Core maybe slangasek can comment on how this could be done?

[Steve Langasek (vorlon)]

This would need to be implemented in snapd, since all of the systemd units for snaps are autogenerated. It's not really a classic vs. core issue.

[John Lenton (chipaca)]

Ordering snapped services wrt system services is something we want to do, but don't have a plan for just yet.