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Kubernetes deployed on ubuntu nodes

This document describes how to deploy kubernetes on ubuntu nodes, including 1 master node and 3 minion nodes, and people uses this approach can scale to any number of minion nodes by changing some settings with ease. Although there exists saltstack based ubuntu k8s installation , it may be tedious and hard for a guy that knows little about saltstack but want to build a really distributed k8s cluster. This new approach of kubernetes deployment is much more easy and automatical than the previous one.

Cloud team from ZJU will keep updating this work.

Prerequisites：

1 The minion nodes have installed docker version 1.2+ and bridge-utils to manipulate linux bridge

2 All machines can communicate with each other, no need to connect Internet (should use private docker registry in this case)

3 These guide is tested OK on Ubuntu 14.04 LTS 64bit server, but it should also work on most Ubuntu versions

4 Dependences of this guide: etcd-2.0.0, flannel-0.4.0, k8s-0.15.0, but it may work with higher versions

5 All the remote servers can be ssh logged in without a password by using key authentication

Main Steps

I. Make kubernetes , etcd and flanneld binaries

First clone the kubernetes github repo, $ git clone https://github.com/GoogleCloudPlatform/kubernetes.git then $ cd kubernetes/cluster/ubuntu.

Then run $ ./build.sh, this will download all the needed binaries into ./binaries.

You can customize your etcd version, flannel version, k8s version by changing variable ETCD_VERSION , FLANNEL_VERSION and K8S_VERSION in build.sh, default etcd version is 2.0.0 , flannel version is 0.4.0 and K8s version is 0.15.0.

Please make sure that there are kube-apiserver, kube-controller-manager, kube-scheduler, kubelet, kube-proxy, etcd, etcdctl and flannel in the binaries/master or binaries/minion directory.

We used flannel here because we want to use overlay network, but please remember it is not the only choice, and it is also not a k8s' necessary dependence. Actually you can just build up k8s cluster natively, or use flannel, Open vSwitch or any other SDN tool you like, we just choose flannel here as a example.

II. Configure and start the kubernetes cluster

An example cluster is listed as below:

IP Address	Role
10.10.103.223	minion
10.10.103.162	minion
10.10.103.250	both master and minion

First configure the cluster information in cluster/ubuntu/config-default.sh, below is a simple sample.

export nodes="vcap@10.10.103.250 vcap@10.10.103.162 vcap@10.10.103.223"

export roles=("ai" "i" "i")

export NUM_MINIONS=${NUM_MINIONS:-3}

export PORTAL_NET=11.1.1.0/24

export FLANNEL_NET=172.16.0.0/16

The first variable nodes defines all your cluster nodes, MASTER node comes first and separated with blank space like <user_1@ip_1> <user_2@ip_2> <user_3@ip_3>

Then the roles variable defines the role of above machine in the same order, "ai" stands for machine acts as both master and minion, "a" stands for master, "i" stands for minion. So they are just defined the k8s cluster as the table above described.

The NUM_MINIONS variable defines the total number of minions.

The PORTAL_NET variable defines the kubernetes service portal ip range. Please make sure that you do have a private ip range defined here.You can use below three private network range accordin to rfc1918. Besides you'd better not choose the one that conflicts with your own private network range.

 10.0.0.0        -   10.255.255.255  (10/8 prefix)

 172.16.0.0      -   172.31.255.255  (172.16/12 prefix)

 192.168.0.0     -   192.168.255.255 (192.168/16 prefix)

The FLANNEL_NET variable defines the IP range used for flannel overlay network, should not conflict with above PORTAL_NET range

After all the above variable being set correctly. We can use below command in cluster/ directory to bring up the whole cluster.

$ KUBERNETES_PROVIDER=ubuntu ./kube-up.sh

The scripts is automatically scp binaries and config files to all the machines and start the k8s service on them. The only thing you need to do is to type the sudo password when promoted. The current machine name is shown below like. So you will not type in the wrong password.


Deploying minion on machine 10.10.103.223

...

[sudo] password to copy files and start minion:

If all things goes right, you will see the below message from console Cluster validation succeeded indicating the k8s is up.

All done !

You can also use kubectl command to see if the newly created k8s is working correctly.

For example, use $ kubectl get minions to see if you get all your minion nodes comming up and ready. It may take some times for the minions be ready to use like below.

NAME                 LABELS             STATUS

10.10.103.162       <none>              Ready

10.10.103.223       <none>              Ready

10.10.103.250       <none>              Ready

Also you can run kubernetes guest-example to build a redis backend cluster on the k8s．

IV. Deploy addons

After the previous parts, you will have a working k8s cluster, this part will teach you how to deploy addones like dns onto the existing cluster.

The configuration of dns is configured in cluster/ubuntu/config-default.sh.


ENABLE_CLUSTER_DNS=true

DNS_SERVER_IP="192.168.3.10"

DNS_DOMAIN="kubernetes.local"

DNS_REPLICAS=1

The DNS_SERVER_IP is defining the ip of dns server which must be in the portal_net range.

The DNS_REPLICAS describes how many dns pod running in the cluster.

After all the above variable have been set. Just type the below command


$ cd cluster/ubuntu

$ KUBERNETES_PROVIDER=ubuntu ./deployAddons.sh

After some time, you can use $ kubectl get pods to see the dns pod is running in the cluster. Done!

IV. Trouble Shooting

Generally, what this approach did is quite simple:

Download and copy binaries and configuration files to proper dirctories on every node
Configure etcd using IPs based on input from user
Create and start flannel network

So, if you see a problem, check etcd configuration first

Please try:

Check /var/log/upstart/etcd.log for suspicious etcd log

Check /etc/default/etcd, as we do not have much input validation, a right config should be like:

ETCD_OPTS="-name infra1 -initial-advertise-peer-urls <http://ip_of_this_node:2380> -listen-peer-urls <http://ip_of_this_node:2380> -initial-cluster-token etcd-cluster-1 -initial-cluster infra1=<http://ip_of_this_node:2380>,infra2=<http://ip_of_another_node:2380>,infra3=<http://ip_of_another_node:2380> -initial-cluster-state new"

You can use below command $ KUBERNETES_PROVIDER=ubuntu ./kube-down.sh to bring down the cluster and run $ KUBERNETES_PROVIDER=ubuntu ./kube-up.sh again to start again.
You can also customize your own settings in /etc/default/{component_name} after configured success.

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