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Adding a Kubernetes Worker Node via Docker

These instructions are very similar to the master set-up above, but they are duplicated for clarity. You need to repeat these instructions for each node you want to join the cluster. We will assume that you have the IP address of the master in ${MASTER_IP} that you created in the master instructions. We’ll need to run several versioned Kubernetes components, so we’ll assume that the version we want to run is ${K8S_VERSION}, which should hold a released version of Kubernetes >= “1.2.0-alpha.6”

Enviroinment variables used:

export MASTER_IP=<the_master_ip_here>
export K8S_VERSION=<your_k8s_version (e.g. 1.2.0-alpha.6)>
export FLANNEL_VERSION=<your_flannel_version (e.g. 0.5.5)>
export FLANNEL_IFACE=<flannel_interface (defaults to eth0)>
export FLANNEL_IPMASQ=<flannel_ipmasq_flag (defaults to true)>

For each worker node, there are three steps:

Set up Flanneld on the worker node

As before, the Flannel daemon is going to provide network connectivity.

Note: This guide expects Docker 1.7.1 or higher.

Set up a bootstrap docker

As previously, we need a second instance of the Docker daemon running to bootstrap the flannel networking.

Run:

sudo sh -c 'docker -d -H unix:///var/run/docker-bootstrap.sock -p /var/run/docker-bootstrap.pid --iptables=false --ip-masq=false --bridge=none --graph=/var/lib/docker-bootstrap 2> /var/log/docker-bootstrap.log 1> /dev/null &'

If you have Docker 1.8.0 or higher run this instead

sudo sh -c 'docker daemon -H unix:///var/run/docker-bootstrap.sock -p /var/run/docker-bootstrap.pid --iptables=false --ip-masq=false --bridge=none --graph=/var/lib/docker-bootstrap 2> /var/log/docker-bootstrap.log 1> /dev/null &'

Important Note: If you are running this on a long running system, rather than experimenting, you should run the bootstrap Docker instance under something like SysV init, upstart or systemd so that it is restarted across reboots and failures.

Bring down Docker

To re-configure Docker to use flannel, we need to take docker down, run flannel and then restart Docker.

Turning down Docker is system dependent, it may be:

sudo /etc/init.d/docker stop

or

sudo systemctl stop docker

or it may be something else.

Run flannel

Now run flanneld itself, this call is slightly different from the above, since we point it at the etcd instance on the master.

sudo docker -H unix:///var/run/docker-bootstrap.sock run -d \
    --net=host \
    --privileged \
    -v /dev/net:/dev/net \
    quay.io/coreos/flannel:${FLANNEL_VERSION} \
    /opt/bin/flanneld \
        --ip-masq=${FLANNEL_IPMASQ} \
        --etcd-endpoints=http://${MASTER_IP}:4001 \
        --iface=${FLANNEL_IFACE}

The previous command should have printed a really long hash, the container id, copy this hash.

Now get the subnet settings from flannel:

sudo docker -H unix:///var/run/docker-bootstrap.sock exec <really-long-hash-from-above-here> cat /run/flannel/subnet.env

Edit the docker configuration

You now need to edit the docker configuration to activate new flags. Again, this is system specific.

This may be in /etc/default/docker or /etc/systemd/service/docker.service or it may be elsewhere.

Regardless, you need to add the following to the docker command line:

--bip=${FLANNEL_SUBNET} --mtu=${FLANNEL_MTU}

Remove the existing Docker bridge

Docker creates a bridge named docker0 by default. You need to remove this:

sudo /sbin/ifconfig docker0 down
sudo brctl delbr docker0

You may need to install the bridge-utils package for the brctl binary.

Restart Docker

Again this is system dependent, it may be:

sudo /etc/init.d/docker start

or it may be:

systemctl start docker

Start Kubernetes on the worker node

Run the kubelet

Again this is similar to the above, but the --api-servers now points to the master we set up in the beginning.

sudo docker run \
    --volume=/:/rootfs:ro \
    --volume=/sys:/sys:ro \
    --volume=/dev:/dev \
    --volume=/var/lib/docker/:/var/lib/docker:rw \
    --volume=/var/lib/kubelet/:/var/lib/kubelet:rw \
    --volume=/var/run:/var/run:rw \
    --net=host \
    --privileged=true \
    --pid=host \
    -d \
    gcr.io/google_containers/hyperkube-amd64:v${K8S_VERSION} \
    /hyperkube kubelet \
        --allow-privileged=true \
        --api-servers=http://${MASTER_IP}:8080 \
        --v=2 \
        --address=0.0.0.0 \
        --enable-server \
        --containerized \
        --cluster-dns=10.0.0.10 \
        --cluster-domain=cluster.local

Run the service proxy

The service proxy provides load-balancing between groups of containers defined by Kubernetes Services

sudo docker run -d \
    --net=host \
    --privileged \
    gcr.io/google_containers/hyperkube-amd64:v${K8S_VERSION} \
    /hyperkube proxy \
        --master=http://${MASTER_IP}:8080 \
        --v=2

Next steps

Move on to testing your cluster or add another node

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