Running Kubernetes locally via Docker

Table of Contents

• Overview
• Prerequisites
• Step One: Run etcd
• Step Two: Run the master
• Step Three: Run the service proxy
• Test it out
• Run an application
• Expose it as a service
• A note on turning down your cluster

Overview

The following instructions show you how to set up a simple, single node Kubernetes cluster using Docker.

Here's a diagram of what the final result will look like:

Prerequisites

1. You need to have docker installed on one machine.
2. Your kernel should support memory and swap accounting. Ensure that the following configs are turned on in your linux kernel:

CONFIG_RESOURCE_COUNTERS=y
    CONFIG_MEMCG=y
    CONFIG_MEMCG_SWAP=y
    CONFIG_MEMCG_SWAP_ENABLED=y
    CONFIG_MEMCG_KMEM=y

1. Enable the memory and swap accounting in the kernel, at boot, as command line parameters as follows:

GRUB_CMDLINE_LINUX="cgroup_enable=memory swapaccount=1"

NOTE: The above is specifically for GRUB2. You can check the command line parameters passed to your kernel by looking at the output of /proc/cmdline:

$cat /proc/cmdline
    BOOT_IMAGE=/boot/vmlinuz-3.18.4-aufs root=/dev/sda5 ro cgroup_enable=memory
    swapaccount=1

Step One: Run etcd

docker run --net=host -d gcr.io/google_containers/etcd:2.0.12 /usr/local/bin/etcd --addr=127.0.0.1:4001 --bind-addr=0.0.0.0:4001 --data-dir=/var/etcd/data

Step Two: Run the master

docker run \
    --volume=/:/rootfs:ro \
    --volume=/sys:/sys:ro \
    --volume=/dev:/dev \
    --volume=/var/lib/docker/:/var/lib/docker:ro \
    --volume=/var/lib/kubelet/:/var/lib/kubelet:rw \
    --volume=/var/run:/var/run:rw \
    --net=host \
    --pid=host \ 
    --privileged=true \
    -d \
    gcr.io/google_containers/hyperkube:v1.0.1 \
    /hyperkube kubelet --containerized --hostname-override="127.0.0.1" --address="0.0.0.0" --api-servers=http://localhost:8080 --config=/etc/kubernetes/manifests

This actually runs the kubelet, which in turn runs a pod that contains the other master components.

Step Three: Run the service proxy

docker run -d --net=host --privileged gcr.io/google_containers/hyperkube:v1.0.1 /hyperkube proxy --master=http://127.0.0.1:8080 --v=2

Test it out

At this point you should have a running Kubernetes cluster. You can test this by downloading the kubectl binary (OS X) (linux)

Note: On OS/X you will need to set up port forwarding via ssh:

boot2docker ssh -L8080:localhost:8080

List the nodes in your cluster by running:

kubectl get nodes

This should print:

NAME        LABELS    STATUS
127.0.0.1   <none>    Ready

If you are running different Kubernetes clusters, you may need to specify -s http://localhost:8080 to select the local cluster.

Run an application

kubectl -s http://localhost:8080 run nginx --image=nginx --port=80

Now run docker ps you should see nginx running. You may need to wait a few minutes for the image to get pulled.

Expose it as a service

kubectl expose rc nginx --port=80

Run the following command to obtain the IP of this service we just created. There are two IPs, the first one is internal (CLUSTER_IP), and the second one is the external load-balanced IP.

kubectl get svc nginx

Alternatively, you can obtain only the first IP (CLUSTER_IP) by running:

kubectl get svc nginx --template={{.spec.clusterIP}}

Hit the webserver with the first IP (CLUSTER_IP):

curl <insert-cluster-ip-here>

Note that you will need run this curl command on your boot2docker VM if you are running on OS X.

A note on turning down your cluster

Many of these containers run under the management of the kubelet binary, which attempts to keep containers running, even if they fail. So, in order to turn down the cluster, you need to first kill the kubelet container, and then any other containers.

You may use docker kill $(docker ps -aq), note this removes all containers running under Docker, so use with caution.