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CRI-O crictl Tutorial

This tutorial will walk you through the creation of Redis server running in a Pod using crictl

It assumes you've already downloaded and configured CRI-O. If not, see here for CRI-O. It also assumes you've set up CNI, and are using the default plugins as described here. If you are using a different configuration, results may vary.

Installation

This section will walk you through installing the following components:

  • crictl - The CRI client for testing.

Get crictl

go get github.com/kubernetes-sigs/cri-tools/cmd/crictl

Ensure the CRI-O service is running

sudo crictl --runtime-endpoint unix:///var/run/crio/crio.sock version

Version:  0.1.0
RuntimeName:  CRI-O
RuntimeVersion:  1.10.0-dev
RuntimeApiVersion:  v1alpha1

to avoid setting --runtime-endpoint when calling crictl, you can run export CONTAINER_RUNTIME_ENDPOINT=unix:///var/run/crio/crio.sock or cp crictl.yaml /etc/crictl.yaml from this repo

Pod Tutorial

Now that the CRI-O components have been installed and configured we are ready to create a Pod. This section will walk you through launching a Redis server in a Pod. Once the Redis server is running we'll use telnet to verify it's working, then we'll stop the Redis server and clean up the Pod.

Creating a Pod

First we need to setup a Pod sandbox using a Pod configuration, which can be found in the CRI-O source tree:

cd $GOPATH/src/github.com/CRI-O/CRI-O

In case the file /etc/containers/policy.json does not exist on your filesystem, make sure that skopeo has been installed correctly. You can use a policy template provided in the CRI-O source tree, but it is insecure and it is not to be used on production machines:

sudo mkdir /etc/containers/
sudo cp test/policy.json /etc/containers

Next create the Pod and capture the Pod ID for later use:

POD_ID=$(sudo crictl runp test/testdata/sandbox_config.json)

Use the crictl command to get the status of the Pod:

sudo crictl inspectp --output table $POD_ID

Output:

ID: cd6c0883663c6f4f99697aaa15af8219e351e03696bd866bc3ac055ef289702a
Name: podsandbox1
UID: redhat-test-crio
Namespace: redhat.test.crio
Attempt: 1
Status: SANDBOX_READY
Created: 2016-12-14 15:59:04.373680832 +0000 UTC
Network namespace: /var/run/netns/cni-bc37b858-fb4d-41e6-58b0-9905d0ba23f8
IP Address: 10.88.0.2
Labels:
	group -> test
Annotations:
	owner -> hmeng
	security.alpha.kubernetes.io/seccomp/pod -> unconfined
	security.alpha.kubernetes.io/sysctls -> kernel.shm_rmid_forced=1,net.ipv4.ip_local_port_range=1024 65000
	security.alpha.kubernetes.io/unsafe-sysctls -> kernel.msgmax=8192

Create a Redis container inside the Pod

Use the crictl command to pull the Redis image, create a Redis container from a container configuration and attach it to the Pod created earlier, while capturing the container ID:

sudo crictl pull quay.io/crio/redis:alpine
CONTAINER_ID=$(sudo crictl create $POD_ID test/testdata/container_redis.json test/testdata/sandbox_config.json)

The crictl create command will take a few seconds to return because the Redis container needs to be pulled.

Start the Redis container:

sudo crictl start $CONTAINER_ID

Get the status for the Redis container:

sudo crictl inspect $CONTAINER_ID

Output:

ID: d0147eb67968d81aaddbccc46cf1030211774b5280fad35bce2fdb0a507a2e7a
Name: podsandbox1-redis
Status: CONTAINER_RUNNING
Created: 2016-12-14 16:00:42.889089352 +0000 UTC
Started: 2016-12-14 16:01:56.733704267 +0000 UTC

Test the Redis container

Connect to the Pod IP on port 6379:

telnet 10.88.0.2 6379

Trying 10.88.0.2...
Connected to 10.88.0.2.
Escape character is '^]'.

At the prompt type MONITOR:

Trying 10.88.0.2...
Connected to 10.88.0.2.
Escape character is '^]'.
MONITOR
+OK

Exit the telnet session by typing ctrl-] and quit at the prompt:

^]

telnet> quit
Connection closed.

Viewing the Redis logs

The Redis logs are logged to the stderr of the crio service, which can be viewed using journalctl:

sudo journalctl -u crio --no-pager

Stop the Redis container and delete the Pod

sudo crictl stop $CONTAINER_ID

sudo crictl rm $CONTAINER_ID

sudo crictl stopp $POD_ID

sudo crictl rmp $POD_ID

sudo crictl pods

sudo crictl ps