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CRICTL User Guide

This document presumes you already have containerd with the cri plugin installed and running.

This document is for developers who wish to debug, inspect, and manage their pods, containers, and container images.

Before generating issues against this document, containerd, containerd/cri, or crictl please make sure the issue has not already been submitted.

Install crictl

If you have not already installed crictl please install the version compatible with the cri plugin you are using. If you are a user, your deployment should have installed crictl for you. If not, get it from your release tarball. If you are a developer the current version of crictl is specified here. A helper command has been included to install the dependencies at the right version:

$ make install-deps
  • Note: The file named /etc/crictl.yaml is used to configure crictl so you don't have to repeatedly specify the runtime sock used to connect crictl to the container runtime:
$ cat /etc/crictl.yaml
runtime-endpoint: unix:///run/containerd/containerd.sock
image-endpoint: unix:///run/containerd/containerd.sock
timeout: 10
debug: true

Download and Inspect a Container Image

The pull command tells the container runtime to download a container image from a container registry.

$ crictl pull busybox
  ...
$ crictl inspecti busybox
  ... displays information about the image.

Note: If you get an error similar to the following when running a crictl command (and your containerd instance is already running):

crictl info
FATA[0000] getting status of runtime failed: rpc error: code = Unimplemented desc = unknown service runtime.v1alpha2.RuntimeService

This could be that you are using an incorrect containerd configuration (maybe from a Docker install). You will need to update your containerd configuration to the containerd instance that you are running. One way of doing this is as follows:

$ mv /etc/containerd/config.toml /etc/containerd/config.bak
$ containerd config default > /etc/containerd/config.toml

Directly Load a Container Image

Another way to load an image into the container runtime is with the load command. With the load command you inject a container image into the container runtime from a file. First you need to create a container image tarball. For example to create an image tarball for a pause container using Docker:

$ docker pull registry.k8s.io/pause:3.7
  3.7: Pulling from pause
  7582c2cc65ef: Pull complete
  Digest: sha256:bb6ed397957e9ca7c65ada0db5c5d1c707c9c8afc80a94acbe69f3ae76988f0c
  Status: Downloaded newer image for registry.k8s.io/pause:3.7
  registry.k8s.io/pause:3.7
$ docker save registry.k8s.io/pause:3.7 -o pause.tar

Then use ctr to load the container image into the container runtime:

# The cri plugin uses the "k8s.io" containerd namespace.
$ sudo ctr -n=k8s.io images import pause.tar
  Loaded image: registry.k8s.io/pause:3.7

List images and inspect the pause image:

$ sudo crictl images
IMAGE                       TAG                 IMAGE ID            SIZE
docker.io/library/busybox   latest              f6e427c148a76       728kB
registry.k8s.io/pause            3.7                 221177c6082a8       311kB
$ sudo crictl inspecti 221177c6082a8
  ... displays information about the pause image.
$ sudo crictl inspecti registry.k8s.io/pause:3.7
  ... displays information about the pause image.

Run a pod sandbox (using a config file)

$ cat sandbox-config.json
{
    "metadata": {
        "name": "nginx-sandbox",
        "namespace": "default",
        "attempt": 1,
        "uid": "hdishd83djaidwnduwk28bcsb"
    },
    "linux": {
    }
}

$ crictl runp sandbox-config.json
e1c83b0b8d481d4af8ba98d5f7812577fc175a37b10dc824335951f52addbb4e
$ crictl pods
PODSANDBOX ID       CREATED             STATE               NAME               NAMESPACE          ATTEMPT
e1c83b0b8d481       2 hours ago         SANDBOX_READY       nginx-sandbox      default            1
$ crictl inspectp e1c8
  ... displays information about the pod and the pod sandbox pause container.
  • Note: As shown above, you may use truncated IDs if they are unique.
  • Other commands to manage the pod include stops ID to stop a running pod and rmp ID to remove a pod sandbox.

Create and Run a Container in the Pod Sandbox (using a config file)

$ cat container-config.json
{
  "metadata": {
      "name": "busybox"
  },
  "image":{
      "image": "busybox"
  },
  "command": [
      "top"
  ],
  "linux": {
  }
}

$ crictl create e1c83 container-config.json sandbox-config.json
0a2c761303163f2acaaeaee07d2ba143ee4cea7e3bde3d32190e2a36525c8a05
$ crictl ps -a
CONTAINER ID        IMAGE               CREATED             STATE               NAME                ATTEMPT
0a2c761303163       docker.io/busybox   2 hours ago         CONTAINER_CREATED   busybox             0
$ crictl start 0a2c
0a2c761303163f2acaaeaee07d2ba143ee4cea7e3bde3d32190e2a36525c8a05
$ crictl ps
CONTAINER ID        IMAGE               CREATED             STATE               NAME                ATTEMPT
0a2c761303163       docker.io/busybox   2 hours ago         CONTAINER_RUNNING   busybox             0
$ crictl inspect 0a2c7
  ... show detailed information about the container

Exec a Command in the Container

$ crictl exec -i -t 0a2c ls
bin   dev   etc   home  proc  root  sys   tmp   usr   var

Display Stats for the Container

$ crictl stats
CONTAINER           CPU %               MEM                 DISK              INODES
0a2c761303163f      0.00                983kB             16.38kB             6
  • Other commands to manage the container include stop ID to stop a running container and rm ID to remove a container.

Display Version Information

$ crictl version
Version:  0.1.0
RuntimeName:  containerd
RuntimeVersion:  1.0.0-beta.1-186-gdd47a72-TEST
RuntimeApiVersion:  v1alpha2

Display Status & Configuration Information about Containerd & The CRI Plugin

$ crictl info
{
  "status": {
    "conditions": [
      {
        "type": "RuntimeReady",
        "status": true,
        "reason": "",
        "message": ""
      },
      {
        "type": "NetworkReady",
        "status": true,
        "reason": "",
        "message": ""
      }
    ]
  },
  "config": {
    "containerd": {
      "snapshotter": "overlayfs",
      "runtime": "io.containerd.runtime.v1.linux"
    },
    "cni": {
      "binDir": "/opt/cni/bin",
      "confDir": "/etc/cni/net.d"
    },
    "registry": {
      "mirrors": {
        "docker.io": {
          "endpoint": [
            "https://registry-1.docker.io"
          ]
        }
      }
    },
    "streamServerPort": "10010",
    "sandboxImage": "registry.k8s.io/pause:3.7",
    "statsCollectPeriod": 10,
    "containerdRootDir": "/var/lib/containerd",
    "containerdEndpoint": "unix:///run/containerd/containerd.sock",
    "rootDir": "/var/lib/containerd/io.containerd.grpc.v1.cri",
    "stateDir": "/run/containerd/io.containerd.grpc.v1.cri",
  },
  "golang": "go1.10"
}

More Information

See here for information about crictl.