[snap] Preseeds are not 'common' that would allow the user to configure them

[Andres Rodriguez]

MAAS allows users to modify the preseeds so they can customize the installation. With the snaps, users are no longer able to do so because the preseeds are not installed in the common, user editable directory.

[Blake Rouse (blake-rouse)]

Probably not the best time to do this but moving them into the database would be much better. As at the moment with HA you would need to modify the preseed across all region controllers.

[Florian Guitton (f-guitton)]

Hello :) Do we know when this is progressing? The documentation does not explicitly mention this limitation, simply stating that "In particular, implementing high availability via snaps is not yet possible". This causes problems as we have now large deployments which we start requiring deployment of supplementary drivers for.
Best regards,

[Cristian Posoiu (cr1st1p)]

When I read the bug description, to me it seemed clear the bug report is about using the snap *common* directory, but the fix is just doing some copy of samples into *SNAP_DATA* and allow use of files from there. Nothing about using SNAP_COMMON.
I think the fix allows one to push preseed files into maas, which is a step forward, but still...

My understanding of Snapd variables is that as a consequence of not using SNAP_COMMON, if you upgrade maas via snap (and it looks like snap got to be the only way to install it), then you say bye-bye to your preseed files.

Is this the intended behavior?

I liked also the observation about this not being HA.
Which also raised in my mind the question about how is HA achieved in regards to the files extracted from distro OSes.

[Alberto Donato (ack)]

Hi, that's not exactly how $SNAP_COMMON vs $SNAP_DATA works.

When a snap is upgraded, the content of the current $SNAP_DATA is copied into the new one.
This allows the application to change those files during (or after) the upgrade process, without affecting the old ones (in case of a revert).

On the other hand, $SNAP_COMMON is a single directory, shared by all snap revisions.

So, both directories work for this case, and any change made to those templates would be carried forward when upgrading the snap.