i/b/block-devices only handle complete devices not partitions

[Peter Sabaini]

Description

The snapd service's block-devices interface currently only allows access to complete disks while individual partitions cannot be accessed. This limitation is impeding the application of MicroCeph.

In deploying MicroCeph, the access to individual partitions of a disk presents a better level of flexibility for granular management of storage, thereby lowering the barrier of entry for deployment

Expected Result

Users should be able to access (r/w) individual disk partitions using the block-devices interface of snapd service for an easier integration with MicroCeph.

Optionally for more granularity the interface could also be implemented with an attribute to control which partitions to access, however an option should be provided to allow access to all partitions.

Thank you!

[Oliver Calder (ocalder)]

Would the existing raw_volume interface [1] be sufficient? It grants r/w permissions to a particular specified partition, as well as r/x access for the mkfs binary to format that partition if necessary [2].

[1]: https://forum.snapcraft.io/t/the-raw-volume-interface/14578
[2]: https://github.com/snapcore/snapd/blob/master/interfaces/builtin/raw_volume.go#L52-L67

[Peter Sabaini (peter-sabaini)]

@ocalder, a bit unsure about this -- the docs say this is for a gadget snap only.

Also aiui we'd need to name the partition we want to access beforehand, is that right? -- but in our case, the user chooses the partition they want to add, so we don't know that at build time