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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:

  • ocid - The implementation of the Kubernetes CRI, which manages Pods.
  • ocic - The ocid 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-rc2/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-rc2
commit: c91b5bea4830a57eac7882d7455d59518cdf70ec
spec: 1.0.0-rc2-dev

ocid

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

Start the ocid 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/bin/ocid --debug
Restart=on-failure
RestartSec=5

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

sudo systemctl daemon-reload

sudo systemctl enable ocid

sudo systemctl start ocid

Ensure the ocid service is running

sudo ocic runtimeversion

VersionResponse: Version: 0.1.0, RuntimeName: runc, RuntimeVersion: 1.0.0-rc2, RuntimeApiVersion: v1alpha1

cni

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

Download the cni source tree:

go get -d github.com/containernetworking/cni

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

Build the cni binaries:

./build

Output:

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

Install the cni binaries:

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 lauching 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 ocic pod run --config test/testdata/sandbox_config.json)

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

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

sudo ocic pod status --id $POD_ID

Output:

ID: cd6c0883663c6f4f99697aaa15af8219e351e03696bd866bc3ac055ef289702a
Name: podsandbox1
UID: redhat-test-ocid
Namespace: redhat.test.ocid
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 ocic command to create a redis container from a container configuration and attach it to the Pod created earlier:

CONTAINER_ID=$(sudo ocic ctr create --pod $POD_ID --config test/testdata/container_redis.json)

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

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

Start the Redis container:

sudo ocic ctr start --id $CONTAINER_ID

Get the status for the Redis container:

sudo ocic 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 ocid service, which can be viewed using journalctl:

sudo journalctl -u ocid --no-pager

Stop the redis container and delete the Pod

sudo ocic ctr stop --id $CONTAINER_ID

sudo ocic ctr remove --id $CONTAINER_ID

sudo ocic pod stop --id $POD_ID

sudo ocic pod remove --id $POD_ID

sudo ocic pod list

sudo ocic ctr list