[Bug 2080892] [NEW] MAAS requires debconf for cloud-init preseed on Ubuntu

[Launchpad Bug Tracker]

You have been subscribed to a public bug by Dan Bungert (dbungert):

MAAS uses curtin to create a cloud-init configuration using curtin's
debconf_selections. Cloud-init's postinst script generates the preseed
configuration based on debconf settings.

This design is undesirable for several reasons:

1. this design unnecessarily requires a distro-specific dependency: debconf
2. this design unnecessarily requires that a duplicate implementation exist in MAAS for Ubuntu core[1][2] and other distros
3. this design obscures project boundaries by hiding MAAS / curtin functionality in cloud-init's packaging shell scripts[3][4]

It would be preferable to use the same (distro-agnostic) method
everywhere. This code path already exists for non-Ubuntu distros and (if
it works) would be much preferable to use everywhere.

This would reduce maintenance burden:

1. it will eliminate duplicate code paths: which may diverge over time
2. it will eliminate hacky shell postinst logic : this would be better implemented in a more maintainable repo/language
3. it will clarify project boundaries and ownership of functionality: this functionality cannot currently be verified by the cloud-init team[5] - a cloud-init devel release is required, followed by MAAS CI runs

[1] https://github.com/canonical/maas/blob/5f6f9d61ae3638c8fa89d0c73e0368a55145667c/src/maasserver/preseed.py#L154
[2] https://github.com/canonical/curtin/blob/a5e8e4ad5c600af9f95e2cecf644d824ca0489e2/curtin/commands/curthooks.py#L1858
[3] https://github.com/canonical/cloud-init/blob/ubuntu/devel/debian/cloud-init.postinst#L54
[4] https://github.com/canonical/cloud-init/issues/5685
[5] https://github.com/canonical/cloud-init/issues/5688
[6] https://github.com/canonical/cloud-init/issues/5685#issuecomment-2342036576

** Affects: maas
     Importance: Undecided
         Status: New

** Affects: cloud-init (Ubuntu)
     Importance: Undecided
         Status: New

** Affects: curtin (Ubuntu)
     Importance: Undecided
         Status: New

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MAAS requires debconf for cloud-init preseed on Ubuntu
https://bugs.launchpad.net/bugs/2080892
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