Re: Difference between Debian cloud images: openstack/generic/genericcloud
Hello,
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:
https://wiki.debian.org/Teams/DPL/OfficialImages
> - 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
discussion.
> - 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,
Ross
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