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Working with `crictl`

docs/how-to/run-kata-with-crictl.md

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Working with crictl

What's cri-tools

cri-tools provides debugging and validation tools for Kubelet Container Runtime Interface (CRI).

cri-tools includes two tools: crictl and critest. crictl is the CLI for Kubelet CRI, in this document, we will show how to use crictl to run Pods in Kata containers.

Note: cri-tools is only used for debugging and validation purpose, and don't use it to run production workloads.

Note: For how to install and configure cri-tools with CRI runtimes like containerd or CRI-O, please also refer to other how-tos.

Use crictl run Pods in Kata containers

Sample config files in this document can be found here.

Run busybox Pod

Run pod sandbox with config file

bash
$ sudo crictl runp -r kata sandbox_config.json
16a62b035940f9c7d79fd53e93902d15ad21f7f9b3735f1ac9f51d16539b836b

$ sudo crictl pods
POD ID              CREATED             STATE               NAME                NAMESPACE           ATTEMPT
16a62b035940f       21 seconds ago      Ready               busybox-pod                             0

Create container in the pod sandbox with config file

bash
$ sudo crictl create 16a62b035940f container_config.json sandbox_config.json
e6ca0e0f7f532686236b8b1f549e4878e4fe32ea6b599a5d684faf168b429202

List containers and check the container is in Created state:

bash
$ sudo crictl ps -a
CONTAINER           IMAGE                              CREATED             STATE               NAME                ATTEMPT             POD ID
e6ca0e0f7f532       docker.io/library/busybox:latest   19 seconds ago      Created             busybox-container   0                   16a62b035940f

Start container

bash
$ sudo crictl start e6ca0e0f7f532
e6ca0e0f7f532

List containers and we can see that the container state has changed from Created to Running:

bash
$ sudo crictl ps
CONTAINER           IMAGE                              CREATED              STATE               NAME                ATTEMPT             POD ID
e6ca0e0f7f532       docker.io/library/busybox:latest   About a minute ago   Running             busybox-container   0                   16a62b035940f

And last we can exec into busybox container:

bash
$ sudo crictl exec -it e6ca0e0f7f532 sh

And run commands in it:

/ # hostname
busybox_host
/ # id
uid=0(root) gid=0(root)

Run redis Pod

In this example, we will create two Pods: one is for redis server, and another one is redis client.

Create redis-server Pod

It's also possible to start a container within a single command:

bash
$ sudo crictl run -r kata redis_server_container_config.json redis_server_sandbox_config.json
bb36e05c599125842c5193909c4de186b1cee3818f5d17b951b6a0422681ce4b

Create redis-client Pod

bash
$ sudo crictl run -r kata redis_client_container_config.json redis_client_sandbox_config.json
e344346c5414e3f51f97f20b2262e0b7afe457750e94dc0edb109b94622fc693

After the new container started, we can check the running Pods and containers.

bash
$ sudo crictl pods
POD ID              CREATED              STATE               NAME                NAMESPACE           ATTEMPT
469d08a7950e3       30 seconds ago       Ready               redis-client-pod                        0
02c12fdb08219       About a minute ago   Ready               redis-server-pod                        0

$ sudo crictl ps
CONTAINER           IMAGE                                  CREATED              STATE               NAME                ATTEMPT             POD ID
e344346c5414e       docker.io/library/redis:6.0.8-alpine   35 seconds ago       Running             redis-client        0                   469d08a7950e3
bb36e05c59912       docker.io/library/redis:6.0.8-alpine   About a minute ago   Running             redis-server        0                   02c12fdb08219

Check redis server is working

To connect to the redis-server. First we need to get the redis-server's IP address.

bash

$ server=$(sudo crictl inspectp 02c12fdb08219 | jq .status.network.ip | tr -d '"' )
$ echo $server
172.19.0.118

Launch redis-cli in the new Pod and connect server running at 172.19.0.118.

bash
$ sudo crictl exec -it e344346c5414e redis-cli -h $server
172.19.0.118:6379> get test-key
(nil)
172.19.0.118:6379> set test-key test-value
OK
172.19.0.118:6379> get test-key
"test-value"

Then back to redis-server, check if the test-key is set in server.

bash
$ sudo crictl exec -it bb36e05c59912 redis-cli get test-key
"test-val"

Returned test-val is just set by redis-cli in redis-client Pod.