[CRIU] [RFC] Introduce v1.1 image format

[Ruslan Kuprieiev]

On 03/31/2015 03:29 PM, Pavel Emelyanov wrote:
> Hi,
>
> Right now we have too many criu-specific file types -- effectively
> every new image file we add is a new "type", we invent a new magic
> number for it and put only it into the header.
>
> One of the difficulty with this approach is that we can't nicely
> teach the "file" utility to spot CRIU-specific files. Too many
> magic should be added and we would have to add new magic numbers
> for every new image type we introduce.

But this patch leaves inventory.img intact, so "file" utility might as 
well just be taught
to spot only inventory magic, because our images are spread across directory
anyway.

Do we really need these changes?
This set also adds another level of confusing complexity to our images 
structure.
Maybe we should rather suggest focusing on V2 images, to make them 
perfect and
not create an intermediate version of non-backward compatible images?

>
> So the proposal is to turn all image files into one format. For
> compatibility reasons the inventory file will have to remain
> intact. But for the rest the common 4-bytes magic is introduced.
> The old-style magic follows one.
>
> There are two more exceptions from this rule -- stats and irmap
> cache files. These two are not images, so these are not changed.
> (Maybe it's worth joining them under "criu service file" magic?)
>
> Older versions of CRIU will not be able to restore from v1.1, but
> that's OK. If we will need it, converting formats would be quite
> easy. Newer CRIU will still understand v1 format, so no crit-based
> conversion required.
>
> -- Pavel
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