Trying out `shiftfs`

Can I use raw.idmap as a safe alternative to shiftfs?

@stgraber Could you maybe update this article, so it reflects the recent situation with idmapped mounts?
(I know of course that this functionality is usually enabled by default, but still it is interesting for people who want to share folders and volumes between host/container or between containers, to know that they can do it without the shiftfs module now)

Additional question:
Are and will the commands be the same (e.g. shift: true
type: disk) as described for example in my howto (LXD usecases of shiftfs (volume-/disk-share)) or will they change?

All the LXD behavior is identical, same config keys, same everything. It will just favor idmapped mounts over shiftfs when usable. Once we have a kernel where that’s true for all cases we care about, shiftfs will go away.

We’re currently hoping this will happen with Ubuntu 22.04 so we don’t need to support shiftfs for another 5 years or more.

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This may not be outdated. According to this bug fix which appears to have been merged and in use, the changes to overlayfs have been reverted because they exposed more serious kernel bugs preventing docker registry from working properly. It seems to me that the overlayfs not working on shiftfs does not work on recent Ubuntu kernels either.