add support for `diff` on running container

[ndeloof]

What is the problem you're trying to solve

Please add support for docker diff to inspect changes to files or directories on a running container

Describe the solution you'd like

$ nerdctl diff <container>
C /etc
D /etc/profile
A /foo

Additional context

No response

[djdongjin]

Not sure if this doable in nerdctl/containerd. I think even docker cannot calcuate this kind of diff when snapshotter is used (if I track the docker cli call correctly, the below func is used when docker diff is callled):

https://github.com/moby/moby/blob/3df160a410b33b3253c7aff814a85322a0883274/daemon/changes.go#L23-L25

[AkihiroSuda]

Not sure if this doable in nerdctl/containerd. I think even docker cannot calcuate this kind of diff when snapshotter is used (if I track the docker cli call correctly, the below func is used when docker diff is callled):

https://github.com/moby/moby/blob/3df160a410b33b3253c7aff814a85322a0883274/daemon/changes.go#L23-L25

They have the diff implementation in the rumpl/moby tree:

• Containerd diff rumpl/moby#91
  (The current implementation seems specific to the overlayfs snapshotter?)

[laurazard]

They have the diff implementation in the rumpl/moby tree:

rumpl/moby#91
(The current implementation seems specific to the overlayfs snapshotter?)

I just tried it and it seems to work fine with other snapshotters (at least stargz).

[islishude]

moby/moby#44964

it's merged

[nrvnrvn]

Does it mean next release of nerdctl will support this?

[AkihiroSuda]

it's merged

Not merged into nerdctl

[islishude]

Landed in 1.7.1 :)

this issue can be closed now.