Using kubeadm to Create a Kubernetes on Ubuntu server
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Docker is great. Managing Docker can be a pain. Docker-compose could not answer on all of the issues. So it always was wrapped with supporting shell scripts, similar to what I have built for docker-splunk. I have heard a lot about Kubernetes, saw it everywhere, have read a lot of articles, but it always felt over complicated for my home infrastructure.
But the day has come. And I am so glad that I have finally looked on Kubernetes, there are so many great things about it, so many features I have missed:
- jobs. No need to have special containers with embedded cron jobs anymore.
- init containers. Forget about building large entrypoint.sh shell scripts in containers to support some special initialization scenarios, just use init containers.
- good dependency management between everything.
- configuration and secrets management out of the box. Forget about hundreds of environment variables.
- ingress out of box.
nginx-proxyis great, but it had some issues with latest versions of docker and docker service.
If you want to play with Kubernetes - use minikube. That will allow you to setup simple single node Kubernetes deployment on VM.
NOTE: docker currently has an issue with time to be out of sync on VM, minikube inherits this issue. See known-issues for details and workaround.
If you are ready for next step - use kubeadm to setup Kubernetes cluster (or single node) on own infrastructure (bare metal).
Just for reference, below are the versions I have used
$ kubeadm version
kubeadm version: version.Info{Major:"1", Minor:"6", GitVersion:"v1.6.5", GitCommit:"490c6f13df1cb6612e0993c4c14f2ff90f8cdbf3", GitTreeState:"clean", BuildDate:"2017-06-14T20:03:38Z", GoVersion:"go1.7.6", Compiler:"gc", Platform:"linux/amd64"}
$ kubectl version
Client Version: version.Info{Major:"1", Minor:"6", GitVersion:"v1.6.6", GitCommit:"7fa1c1756d8bc963f1a389f4a6937dc71f08ada2", GitTreeState:"clean", BuildDate:"2017-06-16T18:34:20Z", GoVersion:"go1.7.6", Compiler:"gc", Platform:"linux/amd64"}
$ sudo docker version
Client:
Version: 17.03.1-ce
API version: 1.27
Go version: go1.7.5
Git commit: c6d412e
Built: Mon Mar 27 17:14:09 2017
OS/Arch: linux/amd64
Server:
Version: 17.03.1-ce
API version: 1.27 (minimum version 1.12)
Go version: go1.7.5
Git commit: c6d412e
Built: Mon Mar 27 17:14:09 2017
OS/Arch: linux/amd64
Experimental: false
$ uname -a
Linux outcoldbuntu 4.8.0-56-generic #61~16.04.1-Ubuntu SMP Wed Jun 14 11:58:22 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux
$ lsb_release -a
Distributor ID: Ubuntu
Description: Ubuntu 16.04.2 LTS
Release: 16.04
Codename: xenial
Install kubernetes on Ubuntu
Mostly just follow the manual from Using kubeadm to Create a Cluster. Few caveats I list below
Docker
Kubernetes does not require latest Docker version. And actually kubeadm showed
a warning that version is higher than latest validated version, which is 1.12
for current moment.
I have not seen any issues with latest version of Docker, and because I already had it installed I kept the latest version.
To install latest Docker just follow the manual on how to install Docker on Ubuntu.
kubeadm
You probably want to use flannel as a pod
network add-on. This add-on works out of box. Manual above suggest you to use
--pod-network-cidr=10.244.0.0/16 with kubeadm init, so don’t forget it
sudo kubeadm init --pod-network-cidr=10.244.0.0/16
Because I am creating one node Kubernetes deployment I needed to use
kubectl taint nodes --all node-role.kubernetes.io/master-
Which allows me to schedule pods on this node.
Also perform the steps to give kubectl access to the kubernetes API
sudo cp /etc/kubernetes/admin.conf $HOME/
sudo chown $(id -u):$(id -g) $HOME/admin.conf
export KUBECONFIG=$HOME/admin.conf
You can also just copy admin.conf under ~/.kube/config, as this is a default
place where kubectl is looking for config.
Network
This is a place, when things start to be more complicated. Kubernetes is built with extensibility in mind, this is why there are always a lot of options.
If you are not sure which network addon to use, use flannel. Reason is quoted
Flannel is a very simple overlay network that satisfies the Kubernetes requirements. Many people have reported success with Flannel and Kubernetes.
To set it up use
$ kubectl apply -f https://raw.githubusercontent.com/coreos/flannel/master/Documentation/kube-flannel-rbac.yml
$ kubectl apply -f https://raw.githubusercontent.com/coreos/flannel/master/Documentation/kube-flannel.yml
After that you should see that current node has a ready status
$ kubectl get nodes
NAME STATUS AGE VERSION
outcoldbuntu Ready 1h v1.6.5
kubectl config
If you want to use multiple clusters from one environment you can manually merge
multiple configuration files into one. For example on my Mac I already used
configuration from minikube, which has been saved under ~/.kube/config. But to
be able to connect to just created cluster on my Ubuntu box I copied admin.conf
file to my local box and merged all the values from admin.conf to ~/.kube/config.
After that I see multiple contexts defined
$ kubectl config get-contexts
CURRENT NAME CLUSTER AUTHINFO NAMESPACE
kubernetes-admin@kubernetes kubernetes kubernetes-admin
* minikube minikube minikube
And I can switch between them
$ kubectl config use-context kubernetes-admin@kubernetes
Switched to context "kubernetes-admin@kubernetes".
Kubernetes Dashboard
To see metrics on Dashboard you need to install Heapster.
The easiest way to start with Heapster and Dashboard is to use official add-on configurations
First create standalone Heapster deployment
kubectl apply -f https://raw.githubusercontent.com/kubernetes/kops/master/addons/monitoring-standalone/v1.6.0.yaml
After that create dashboard deployment
kubectl apply -f https://raw.githubusercontent.com/kubernetes/kops/master/addons/kubernetes-dashboard/v1.6.0.yaml
You can get access to the dashboard now
$ kubectl proxy
And open http://localhost:8001/ui