[pve-devel] [PATCH storage/qemu-server/pve-manager] implement ova/ovf import for directory type storages

[Dominik Csapak]

On 4/18/24 12:35, Fiona Ebner wrote:
> Am 18.04.24 um 11:27 schrieb Dominik Csapak:
>> ok after a bit of thinking and discussing off-list
>> the plan to go forward from my side is this:
>>
>> (please tell if there is something obviously wrong with it or you'd
>> strongly prefer something differently)
>>
>> extract on demand vs on upload:
>>   i'd go with extract on demand because managing the extraction of the
>> tarball + subdir etc is not really a win in my book, since we have to
>> have most safeguards anyway and we have the same
>> issue of where to store/map it etc. also it's not convenient for users
>> that have already
>> a bunch of ovas and want to store them in a central place, now they'd
>> have to extract
>> them just for us (and importing should be as small a hassle as it can be)
>>
> 
> The upside is that it would avoid all the extra cleanup handling and be
> more efficient for users that want to import from a single OVA multiple
> times. But you are right, the downside is also very big.
> 
> I'm thinking now, is there no way to expose a file in an OVA/tar without
> actually extracting it? I.e. something like
> 
>> root at pve8a1 ~ # cat B
>> secret
>> root at pve8a1 ~ # tar cf arch.tar A B dir
>> root at pve8a1 ~ # losetup --offset 1536 --sizelimit 512 --read-only --show -f arch.tar
>> /dev/loop0
>> root at pve8a1 ~ # cat /dev/loop0
>> secret
> 
> but that doesn't seem to work with sizelimit < 512. Not claiming losetup
> is a good mechanism for that, just to illustrate the idea.


AFAIU that only works for uncompressed tars and ova can by definition
be compressed, so that won't work reliably

there is archivemount[0], which can fuse mount archives

i tested that, and it's *very* slow for randomly accessing the files inside
(i guess because it must seek much further back to get the compression
state correct)

i tested a qemu-img convert from such a file and it took >10 minutes
for a file that would normally be extracted + converted in under a minute

0: https://github.com/cybernoid/archivemount