[RFC] inspect: show mounts info from CRI/ctr containers

[zjumoon01]

Fix #2934

Containers created by CRI or ctr with bind mounts
don't have label nerdct/mounts.

However, 'inspect' with dockercompat mode only parses mounts from label "nerdct/mounts".

After this patch, 'inspect' with dockercompat mode can show CRI and ctr container bind mounts.

ResolvConfPath, HostnamePath and Hostname are taken to the same consideration.

Further comments:

1. only show bind mount from CRI/ ctr containers. Because native container mounts contain all types of mount, such as tmpfs, proc, sysfs. That are not expected as dockercompat
2. nerdctl/mounts in label has higher priority. So do nerdctl/hostname and nerdctl/state-dir. CRI/ctr mounts and label "nerdct/mounts" are not merged. It shouldn't happen that container created by nerdctl with bind mount doesn't inject mount info to label nerdctl/mounts

How to test:

ctr:

ctr run -d --mount type=bind,src=/home/ttt/test,dst=/disk002,options=rbind:rw docker.io/library/ubuntu:22.04 test-c1 sleep 200

Before this patch

#nerdctl -n default inspect test-c1 | grep -i mounts
"Mounts": null,

After this patch

#nerdctl -n default inspect test-c1 | grep -i mounts -A 10
"Mounts": [
{
"Type": "bind",
"Source": "/home/ttt/test",
"Destination": "/disk002",
"Mode": "",
"RW": true,
"Propagation": ""
}
],
"Config": {

#nerdctl -n default inspect test-c1 -f {{.Mounts}}
[{bind /home/ttt/test /disk002 true }]

We can also test ResolvConf and hostname by crictl pod

[zjumoon01]

test crictl container

pod.json
{ "metadata": { "name": "testpod", "namespace": "default" }, "hostname": "myhostname", "log_directory": "/var/log/podlog" }

container.json
{ "metadata": { "name": "test-container" }, "image":{ "image": "docker.io/library/ubuntu:22.04" }, "command": [ "/bin/sh" ], "args": [ "-c", "sleep infinity" ], "log_path":"ubuntu.0.log", "linux": { }, "mounts": [ { "container_path": "/tmp", "host_path": "/tmp" } ] }

podid=`crictl runp pod.json`
container=`crictl create $podid container.json pod.json`
crictl start $container

nerdctl inspect -f {{.Config.Hostname}} $container
myhostname

nerdctl inspect -f {{.HostnamePath}} $container
/home/containerd/io.containerd.grpc.v1.cri/sandboxes/cdeae27e72b9bd8de07b8f7f938d2606767a88342c6531c7913c8422bbb17065/hostname

nerdctl inspect -f {{.ResolvConfPath}} $container
/home/containerd/io.containerd.grpc.v1.cri/sandboxes/cdeae27e72b9bd8de07b8f7f938d2606767a88342c6531c7913c8422bbb17065/resolv.conf

[AkihiroSuda]

Can we have a test?

[zjumoon01]

Can we have a test?

OK.
I have added a test and split into two commits.

[djdongjin]

nit: we can use else if at line 241 to save an unnecessary if.

[zjumoon01]

Fixed.

[djdongjin]

LGTM other than some minor comments, thanks

[djdongjin]

nit: it'll be easier to visualize if you use raw string, eg.

expectedLabelMount := `[{"Type":"bind","Source":"/tmp",...}]`

[djdongjin]

do you still have more tests to add?

[zjumoon01]

do you still have more tests to add?

No.
There were never tests for internal labels, such as “containerd.io/restart.status” and "nerdctl/hostname", that are beyond the scope of this commit.

[djdongjin]

LGTM, thanks

[AkihiroSuda]

Thanks