Add tar as a disk_format to glance

[Arun S A G]

We are adding support OS tarball images in ironic project. This feature depends on adding new value tar to disk_format. Please see https://review.openstack.org/#/c/248968/

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/270575

[Brian Rosmaita (brian-rosmaita)]

This is a little weird, because a tarball is usually thought of as a container of stuff. Could you explain why you want 'tar' as a 'disk_format' ? It does make sense because a 'container' in the Glance sense is package containing an image and also some metadata about the image. I mean, if you don't include any such metadata in the tarball, then I guess these new Ironic images would appropriately be disk_format == tar, container_format == bare. It sounds from the Ironic spec that the contents of the tarball will be raw partitions that Ironic will write directly onto the system disk? So maybe it's more appropriate to have disk_format == raw, container_format == tar?

[Arun S A G (sagarun)]

There is no metadata in the tarball. By OS tarball i mean it is a compressed tar archive of a / (root filesystem). These tarballs are created by first installing the OS packages in a chroot and then compressing the chroot as tar.*.

So here the disk_format == tar and the container_format ==bare

[Brian Rosmaita (brian-rosmaita)]

This is a bit premature in that the spec to add this functionality to Ironic hasn't been approved yet.

That being said, your explanation above makes sense for tar being a disk format in a bare container. In fact, I can imagine someone taking one of these tarballs, creating a metadata file for it, and packaging it as an OVA.

We discussed this at the Glance meeting on 28 Jan 2016, and from the discussion there, it looks like the syntactic identifier 'tar' for such an image is confusing. So how about 'os_tarball' (for "operating system tarball")?

I'm just floating the idea at the moment, because Glance isn't going to want to move on this until it's clear that Ironic has accepted your spec. (While you are testing, etc., you can use a Glance that's configured to recognize the os_tarball identifier -- just change the value of container_formats in /etc/glance/glance-api.conf)

[Arun S A G (sagarun)]

Thank you for starting the discussion! All i wanted to see was how glance feels about this. I will let ironic know the status of this feature and update the spec.

To be clear.
disk_format == os_tarball and container_format == bare

is that your proposal? If so i think it makes sense.

[Brian Rosmaita (brian-rosmaita)]

Yes, disk_format == os_tarball and container_format == bare.

At the moment, though, I'm just speaking for myself, I'm not sure what the wider Glance community will think of the 'os_tarball' identifier, though it seemed pretty clear from the discussion yesterday that 'tar' is going to confuse people, so we'll definitely want something other than 'tar'.

[Stuart McLaren (stuart-mclaren)]

Is a tarball a disk format?

I think it's possible to "mount" all our existing disk_format types.

For Docker (also a tar ball) we used container format.

I'd probably just go for container_format = 'tar' and, to avoid confusion, document exactly what it means here: http://docs.openstack.org/developer/glance/formats.html

[OpenStack Infra (hudson-openstack)]

Change abandoned by Nikhil Komawar (<email address hidden>) on branch: master
Review: https://review.openstack.org/270575
Reason: I see no movement on this patch and/or the associate bug. Please reopen as/when you find appropriate.

[Brian Rosmaita (brian-rosmaita)]

No action on this in 2 years, changing to "opinion".