Background
kubernetes dockershim will be removed in upcoming v1.24.
When dockershim is removed, it will not be doable using docker command to check the localhost containers.
docker command is not necessary in kubernetes aspect since kubectl exec will take care of the same operation using CRI(Container Runtime Interface), but developer tends to debug localhost container with docker command to see if what is going on in the specific container.
So let's,
- play with
ctrcommand that comes withcontainerd. - control ROS 2 container with
ctras example.
ctr command
- It is still unsupported debug and administrative CLI...
NAME:
ctr -
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containerd CLI
USAGE:
ctr [global options] command [command options] [arguments...]
VERSION:
1.5.5-0ubuntu3~20.04.2
DESCRIPTION:
ctr is an unsupported debug and administrative client for interacting
with the containerd daemon. Because it is unsupported, the commands,
options, and operations are not guaranteed to be backward compatible or
stable from release to release of the containerd project.
- download image and list
tomoyafujita@~/DVT >sudo ctr image pull docker.io/library/hello-world:latest
docker.io/library/hello-world:latest: resolved |++++++++++++++++++++++++++++++++++++++|
index-sha256:bfea6278a0a267fad2634554f4f0c6f31981eea41c553fdf5a83e95a41d40c38: done |++++++++++++++++++++++++++++++++++++++|
manifest-sha256:f54a58bc1aac5ea1a25d796ae155dc228b3f0e11d046ae276b39c4bf2f13d8c4: done |++++++++++++++++++++++++++++++++++++++|
layer-sha256:2db29710123e3e53a794f2694094b9b4338aa9ee5c40b930cb8063a1be392c54: done |++++++++++++++++++++++++++++++++++++++|
config-sha256:feb5d9fea6a5e9606aa995e879d862b825965ba48de054caab5ef356dc6b3412: done |++++++++++++++++++++++++++++++++++++++|
elapsed: 2.2 s total: 5.4 Ki (2.5 KiB/s)
unpacking linux/amd64 sha256:bfea6278a0a267fad2634554f4f0c6f31981eea41c553fdf5a83e95a41d40c38...
done: 68.620298ms
tomoyafujita@~/DVT >sudo ctr images list
REF TYPE DIGEST SIZE PLATFORMS LABELS
docker.io/library/hello-world:latest application/vnd.docker.distribution.manifest.list.v2+json sha256:bfea6278a0a267fad2634554f4f0c6f31981eea41c553fdf5a83e95a41d40c38 6.9 KiB linux/386,linux/amd64,linux/arm/v5,linux/arm/v7,linux/arm64/v8,linux/mips64le,linux/ppc64le,linux/riscv64,linux/s390x,windows/amd64 -
- run container and start application
tomoyafujita@~/DVT >sudo ctr container create docker.io/library/hello-world:latest demo
tomoyafujita@~/DVT >sudo ctr container list
CONTAINER IMAGE RUNTIME
demo docker.io/library/hello-world:latest io.containerd.runc.v2
tomoyafujita@~/DVT >sudo ctr task start demo
Hello from Docker!
This message shows that your installation appears to be working correctly.
To generate this message, Docker took the following steps:
1. The Docker client contacted the Docker daemon.
2. The Docker daemon pulled the "hello-world" image from the Docker Hub.
(amd64)
3. The Docker daemon created a new container from that image which runs the
executable that produces the output you are currently reading.
4. The Docker daemon streamed that output to the Docker client, which sent it
to your terminal.
To try something more ambitious, you can run an Ubuntu container with:
$ docker run -it ubuntu bash
Share images, automate workflows, and more with a free Docker ID:
https://hub.docker.com/
For more examples and ideas, visit:
https://docs.docker.com/get-started/
- remove container
tomoyafujita@~/DVT >sudo ctr container list
CONTAINER IMAGE RUNTIME
demo docker.io/library/hello-world:latest io.containerd.runc.v2
tomoyafujita@~/DVT >sudo ctr container rm demo
tomoyafujita@~/DVT >sudo ctr container list
CONTAINER IMAGE RUNTIME
- debug container (with busybox image)
tomoyafujita@~/DVT >sudo ctr i pull docker.io/library/busybox:latest
docker.io/library/busybox:latest: resolved |++++++++++++++++++++++++++++++++++++++|
index-sha256:caa382c432891547782ce7140fb3b7304613d3b0438834dce1cad68896ab110a: done |++++++++++++++++++++++++++++++++++++++|
manifest-sha256:14d4f50961544fdb669075c442509f194bdc4c0e344bde06e35dbd55af842a38: done |++++++++++++++++++++++++++++++++++++++|
layer-sha256:554879bb300427c7301c1cbdf266a7eba24a85b10d19f270b3d348b9eb9ca7df: done |++++++++++++++++++++++++++++++++++++++|
config-sha256:2fb6fc2d97e10c79983aa10e013824cc7fc8bae50630e32159821197dda95fe3: done |++++++++++++++++++++++++++++++++++++++|
elapsed: 2.2 s total: 4.2 Ki (1.9 KiB/s)
unpacking linux/amd64 sha256:caa382c432891547782ce7140fb3b7304613d3b0438834dce1cad68896ab110a...
done: 80.719287ms
tomoyafujita@~/DVT >sudo ctr container create docker.io/library/busybox:latest busyboxdemo
tomoyafujita@~/DVT >sudo ctr container list
CONTAINER IMAGE RUNTIME
busyboxdemo docker.io/library/busybox:latest io.containerd.runc.v2
tomoyafujita@~/DVT >sudo ctr task start -d busyboxdemo
tomoyafujita@~/DVT >sudo ctr task list
TASK PID STATUS
busyboxdemo 35058 RUNNING
tomoyafujita@~/DVT >sudo ctr task exec -t --exec-id bashdemo busyboxdemo sh
/ # ls
bin dev etc home proc root run sys tmp usr var
/ # whoami
root
/ # exit
tomoyafujita@~/DVT >sudo ctr task rm -f busyboxdemo
WARN[0000] task busyboxdemo exit with non-zero exit code 137
tomoyafujita@~/DVT >sudo ctr task list
TASK PID STATUS
tomoyafujita@~/DVT >sudo ctr container list
CONTAINER IMAGE RUNTIME
busyboxdemo docker.io/library/busybox:latest io.containerd.runc.v2
tomoyafujita@~/DVT >sudo ctr container delete busyboxdemo
tomoyafujita@~/DVT >sudo ctr container list
CONTAINER IMAGE RUNTIME
Iterate with Docker Container (ros:rolling)
- start docker ros:rolling container
tomoyafujita@~/DVT >docker pull ros:rolling
rolling: Pulling from library/ros
...
tomoyafujita@~/DVT >docker run -it --privileged --network host --name ros2_rolling -e DISPLAY=unix$DISPLAY -v /tmp/.X11-unix:/tmp/.X11-unix -v /home/tomoyafujita/DVT/docker_ws:/root/docker_ws ros:rolling
tomoyafujita@~/DVT >docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
7900668f4e07 ros:rolling "/ros_entrypoint.sh …" About an hour ago Up About an hour ros2_rolling
-
Docker images cannot be managed via
ctr
Not really sure about details, but storage and APIs are different between docker and ctr, so that they cannot cross-manage each other. -
containerd-shimuses namespace and id for each container initiated by docker.
tomoyafujita@~/DVT >sudo ctr container list
CONTAINER IMAGE RUNTIME
(we cannot see any container runtime)
tomoyafujita@~/DVT >ps -ef | grep containerd-shim
root 17136 1 0 16:14 ? 00:00:00 /usr/bin/containerd-shim-runc-v2 -namespace moby -id 7900668f4e07706c18328ef66037a8a93a86e254b0d2547b93c747b2646f1411 -address /run/containerd/containerd.sock
(we can see it uses namespace moby)
tomoyafujita@~/DVT >sudo ctr -n moby container list
CONTAINER IMAGE RUNTIME
7900668f4e07706c18328ef66037a8a93a86e254b0d2547b93c747b2646f1411 - io.containerd.runc.v2
(and this container id is printed as docker container id)
tomoyafujita@~/DVT >docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
7900668f4e07 ros:rolling "/ros_entrypoint.sh …" About an hour ago Up About an hour ros2_rolling
^^^^^^^^^^^^ HERE
- debug ros:rolling container
tomoyafujita@~/DVT >sudo ctr -n moby task list
TASK PID STATUS
7900668f4e07706c18328ef66037a8a93a86e254b0d2547b93c747b2646f1411 17164 RUNNING
tomoyafujita@~/DVT >sudo ctr -n moby task exec -t --exec-id bashdemo 7900668f4e07706c18328ef66037a8a93a86e254b0d2547b93c747b2646f1411 bash
root@tomoyafujita-HP-Compaq-Elite-8300-SFF:/# source /opt/ros/rolling/setup.bash
root@tomoyafujita-HP-Compaq-Elite-8300-SFF:/# ros2 daemon status
The daemon is not running
Trouble Shooting
- root permission required
tomoyafujita@~/DVT >ctr images list
ctr: failed to dial "/run/containerd/containerd.sock": connection error: desc = "transport: error while dialing: dial unix /run/containerd/containerd.sock: connect: permission denied"
tomoyafujita@~/DVT >sudo ls -lt /run/containerd/containerd.sock
[sudo] password for tomoyafujita:
srw-rw---- 1 root root 0 Mar 29 15:38 /run/containerd/containerd.sock
containerd rootless mode, see https://github.com/containerd/containerd/blob/main/docs/rootless.md