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cri-o Tutorial

This tutorial will walk you through the installation of cri-o, an Open Container Initiative-based implementation of Kubernetes Container Runtime Interface, and the creation of Redis server running in a Pod.

Prerequisites

A Linux machine is required to download and build the cri-o components and run the commands in this tutorial.

Create a machine running Ubuntu 16.10:

gcloud compute instances create cri-o \
  --machine-type n1-standard-2 \
  --image-family ubuntu-1610 \
  --image-project ubuntu-os-cloud

SSH into the machine:

gcloud compute ssh cri-o

Installation

This section will walk you through installing the following components:

  • crio - The implementation of the Kubernetes CRI, which manages Pods.
  • crioctl - The crio client for testing.
  • cni - The Container Network Interface
  • runc - The OCI runtime to launch the container

runc

Download the runc release binary:

wget https://github.com/opencontainers/runc/releases/download/v1.0.0-rc4/runc-linux-amd64

Set the executable bit and copy the runc binary into your PATH:

chmod +x runc-linux-amd64

sudo mv runc-linux-amd64 /usr/bin/runc

Print the runc version:

runc -version

runc version 1.0.0-rc4
commit: 2e7cfe036e2c6dc51ccca6eb7fa3ee6b63976dcd
spec: 1.0.0

crio

The crio project does not ship binary releases so you'll need to build it from source.

Install the Go runtime and tool chain

Download the Go 1.7.4 binary release:

wget https://storage.googleapis.com/golang/go1.7.4.linux-amd64.tar.gz

Install Go 1.7.4:

sudo tar -xvf go1.7.4.linux-amd64.tar.gz -C /usr/local/

mkdir -p $HOME/go/src

export GOPATH=$HOME/go

export PATH=$PATH:/usr/local/go/bin:$GOPATH/bin

At this point the Go 1.7.4 tool chain should be installed:

go version

go version go1.7.4 linux/amd64

Build crio from source

sudo apt-get install -y libglib2.0-dev libseccomp-dev libapparmor-dev

go get -d github.com/kubernetes-incubator/cri-o

cd $GOPATH/src/github.com/kubernetes-incubator/cri-o

make install.tools

make

sudo make install

Output:

install -D -m 755 kpod /usr/local/bin/kpod
install -D -m 755 crio /usr/local/bin/crio
install -D -m 755 crioctl /usr/local/bin/crioctl
install -D -m 755 conmon/conmon /usr/local/libexec/crio/conmon
install -D -m 755 pause/pause /usr/local/libexec/crio/pause
install -d -m 755 /usr/local/share/man/man{1,5,8}
install -m 644 docs/kpod.1 docs/kpod-launch.1 -t /usr/local/share/man/man1
install -m 644 docs/crio.conf.5 -t /usr/local/share/man/man5
install -m 644 docs/crio.8 -t /usr/local/share/man/man8
install -D -m 644 crio.conf /etc/crio/crio.conf
install -D -m 644 seccomp.json /etc/crio/seccomp.json

If you are installing for the first time, generate config as follows:

make install.config

Output:

install -D -m 644 crio.conf /etc/crio/crio.conf
install -D -m 644 seccomp.json /etc/crio/seccomp.json

Start the crio system daemon

sudo sh -c 'echo "[Unit]
Description=OCI-based implementation of Kubernetes Container Runtime Interface
Documentation=https://github.com/kubernetes-incubator/cri-o

[Service]
ExecStart=/usr/local/bin/crio --debug
Restart=on-failure
RestartSec=5

[Install]
WantedBy=multi-user.target" > /etc/systemd/system/crio.service'

sudo systemctl daemon-reload

sudo systemctl enable crio

sudo systemctl start crio

Ensure the crio service is running

sudo crioctl runtimeversion

VersionResponse: Version: 0.1.0, RuntimeName: runc, RuntimeVersion: 1.0.0-rc4, RuntimeApiVersion: v1alpha1

CNI plugins

This tutorial will use the latest version of CNI plugins from the master branch and build it from source.

Download the CNI plugins source tree:

go get -d github.com/containernetworking/plugins

cd $GOPATH/src/github.com/containernetworking/plugins

Build the CNI plugins:

./build.sh

Output:

Building API
Building reference CLI
Building plugins
   flannel
   tuning
   bridge
   ipvlan
   loopback
   macvlan
   ptp
   dhcp
   host-local
   noop

Install the CNI plugins:

sudo mkdir -p /opt/cni/bin

sudo cp bin/* /opt/cni/bin/

Configure CNI

sudo mkdir -p /etc/cni/net.d

sudo sh -c 'cat >/etc/cni/net.d/10-mynet.conf <<-EOF
{
    "cniVersion": "0.2.0",
    "name": "mynet",
    "type": "bridge",
    "bridge": "cni0",
    "isGateway": true,
    "ipMasq": true,
    "ipam": {
        "type": "host-local",
        "subnet": "10.88.0.0/16",
        "routes": [
            { "dst": "0.0.0.0/0"  }
        ]
    }
}
EOF'

sudo sh -c 'cat >/etc/cni/net.d/99-loopback.conf <<-EOF
{
    "cniVersion": "0.2.0",
    "type": "loopback"
}
EOF'

At this point CNI is installed and configured to allocation IP address to containers from the 10.88.0.0/16 subnet.

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/kubernetes-incubator/cri-o

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

POD_ID=$(sudo crioctl pod run --config test/testdata/sandbox_config.json)

sudo crioctl pod run --config test/testdata/sandbox_config.json

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

sudo crioctl pod status --id $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 crioctl command to pull the redis image, create a redis container from a container configuration and attach it to the Pod created earlier:

sudo crioctl image pull redis:alpine
CONTAINER_ID=$(sudo crioctl ctr create --pod $POD_ID --config test/testdata/container_redis.json)

sudo crioctl ctr create --pod $POD_ID --config test/testdata/container_redis.json

The crioctl ctr create command will take a few seconds to return because the redis container needs to be pulled.

Start the Redis container:

sudo crioctl ctr start --id $CONTAINER_ID

Get the status for the Redis container:

sudo crioctl ctr status --id $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 crioctl ctr stop --id $CONTAINER_ID

sudo crioctl ctr remove --id $CONTAINER_ID

sudo crioctl pod stop --id $POD_ID

sudo crioctl pod remove --id $POD_ID

sudo crioctl pod list

sudo crioctl ctr list