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Re: Difference between Debian cloud images: openstack/generic/genericcloud


On Wed, Mar 31, 2021 at 05:18:34PM +0300, Vitaly Potyarkin wrote:
> I'm trying to understand the differences in content and support status of
> Debian cloud images found here [1]. It seems to me that Openstack, generic and
> genericcloud serve more or less the same purpose - and I'm failing to
> understand when to use which.
> Here is what I've gathered so far:
> - Openstack image seems to be the go to one for all use cases, even outside of
>   Openstack deployments. It also has a more "official" vibe to it, being
>   grouped into the same section as CD/DVD installer images at this page [2]

That is kind of misleading, it's no more or less official than the others.
They are all built according to the policy at:

> - Generic and genericcloud images are listed under "misc and unofficial stuff"
>   at [2] and provide no stable URLs for the latest build - that suggests these
>   images are somehow inferior to the Openstack ones.

The openstack images provide a stable URL for the latest, but the other images
do not.  Currently, it's up to the client to choose.  It should be easy, they
are named by iso date.

> - Image size differs drastically between Openstack (535M) and generic (285M),
>   genericcloud (222M) images. Package list diffs show that openstack adds
>   some packages like aptitude, python2.7 and firmware-linux-free - but I'm not
>   sure that those are enough to account for the twice larger size, especially
>   since generic/genericcloud add some packages too (bridge-utils, curl,
>   chrony, man-db, manpages, ethtool, etc). Maybe there are some differences in
>   the build process?

The openstack images have a different build process, and the maintainer has
made different choices regarding preinstalled software.  There's other details
regarding the filesystem shrinking- if you care, the list archives contain some

> - The only difference between generic and genericcloud seems to be the kernel:
>   linux-image-amd64 in generic and linux-image-cloud-amd64 in genericcloud.
>   For some reason the -cloud kernel is significantly smaller, even though
>   package description [3] makes no mention of omitted modules (drivers?)

Yes, the kernel is the only difference.  The cloud kernel omits modules that
are unlikely to be useful in a cloud environment.  The details are too large
for the package description, if you care, diff the configs they ship.

> My use case is pretty simple: I'm just looking for a base image to spawn new
> virtual machines under libvirt/kvm with cloud-init. I'm inclined to go with
> smaller genericcloud images, but I'm a little worried that there are some
> hidden footguns I'm not aware of. Wiki page [4] has no mention of generic
> cloud images, could someone knowledgeable explain the differences please?

genericcloud should work.  But if you're worried and don't want to mess with
it, generic is a more conservative choice.

Hope that helps,

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