Can nerdctl/crictl be used to list containers started by docker

Question

I'm using version 20.10.21 of docker, in my understanding docker with this version uses containerd to manage image and container lifecycle, but why cannot I use crictl/nerdctl to list the containers which I started by docker cli?

What I've tried:

1. Check if docker uses containerd to manage contianers, ths is the result of systemctl status docker

 docker.service - Docker Application Container Engine 
 Loaded: loaded (/usr/lib/systemd/system/docker.service; disabled; preset: disabled)
Drop-In: /etc/systemd/system/docker.service.d
         └─http-proxy.conf
 Active: active (running) since Sun 2022-12-04 22:44:27 CST; 1min 18s ago TriggeredBy: ● docker.socket
   Docs: https://docs.docker.com    Main PID: 1821 (dockerd)
  Tasks: 91 (limit: 38297)
 Memory: 229.6M
    CPU: 1.214s
 CGroup: /system.slice/docker.service
         ├─1821 /usr/bin/dockerd -H fd://
         ├─1845 containerd --config /var/run/docker/containerd/containerd.toml --log-level info

I guess this means containerd is started by docker daemon. And the unix socket is located at /var/run/docker/containerd/containerd.sock

2. Try nerdctl to list containers but got error message:

$ nerdctl --address unix:///var/run/docker/containerd/containerd.sock ps  
FATA[0000] rootless containerd not running? (hint: use `containerd-rootless-setuptool.sh install` to start rootless  containerd): stat /run/user/1000/containerd-rootless: no such file or directory

Then I tried it again with sudo

sudo nerdctl --address  unix:///var/run/docker/containerd/containerd.sock ps  
CONTAINER ID  IMAGE    COMMAND    CREATED    STATUS    PORTS    NAMES

As you can see, there's no container listed, but docker ps shows many containers I started.

3. Try crictl to check result, but got errors:

sudo crictl --r unix:///var/run/docker/containerd/containerd.sock ps
E1204 22:47:27.190569    3925 remote_runtime.go:557] "ListContainers with filter from runtime service failed" err="rpc error: code = Unimplemented desc = unknown service runtime.v1alpha2.RuntimeService" filter="&ContainerFilter{Id:,State:&ContainerStateValue{State:CONTAINER_RUNNING,},PodSandboxId:,LabelSelector:map[string]string{},}"
FATA[0000] listing containers: rpc error: code = Unimplemented desc = unknown service runtime.v1alpha2.RuntimeService 

So my questions is: Why can't I get the same results of docker cli by nerdctl/crictl? Is there anything wrong I've done? or anything wrong in my understanding?

Thanks for any tips.

Answer 1

It looks like the namespace is not specified in your command. Adding --namespace moby shows Docker containers. Leaving out the namespace defaults to a namespace named "default".