Tag: Kubernetes

Multi node Kubernetes cluster on Vagrant

This is fast and easy way to install Kubernetes on Vagrant with Metrics server addon.

git clone https://github.com/vorozhko/practical-guide-to-kubernetes-administration-exam
cd vagrant/kubernetes
vagrant up

At this point you would have one master node and two worker nodes ready.

Lets check cluster health

vagrant ssh master

kubectl get nodes
NAME      STATUS   ROLES    AGE     VERSION
master    Ready    master   2m46s   v1.18.2
worker1   Ready    <none>   35s     v1.18.2
worker2   Ready    <none>   32s     v1.18.2

All nodes are ready.

Lets install Metrics server addon

kubectl apply -f https://github.com/kubernetes-sigs/metrics-server/releases/download/v0.3.6/components.yaml

Update metrics server startup flags to solve nodes name resolution issue

kubectl -n kube-system edit deployment metrics-server

#Add following settings to metrics-server start command
- --kubelet-preferred-address-types=InternalIP,Hostname,InternalDNS,ExternalDNS,ExternalIP
- --kubelet-insecure-tls

At this point Metrics server is installed.

After about few minutes of collecting data you should see:

kubectl top node
NAME      CPU(cores)   CPU%   MEMORY(bytes)   MEMORY%   
master    264m         13%    1091Mi          57%       
worker1   109m         5%     746Mi           39%       
worker2   109m         5%     762Mi           40% 

kubectl top pod
NAME                                       CPU(cores)   MEMORY(bytes)   
calico-kube-controllers-75d56dfc47-bdsxr   1m           5Mi             
calico-node-rvqwp                          20m          23Mi            
calico-node-thtd4                          31m          25Mi            
calico-node-vkhgs                          23m          22Mi            
coredns-66bff467f8-x68zs                   4m           5Mi             
coredns-66bff467f8-z7kzh                   4m           10Mi            
etcd-master                                22m          39Mi            
kube-apiserver-master                      52m          352Mi           
kube-controller-manager-master             18m          55Mi            
kube-proxy-tdwpf                           1m           18Mi            
kube-proxy-wvsb9                           1m           8Mi             
kube-proxy-zfd2c                           1m           9Mi             
kube-scheduler-master                      5m           23Mi            
metrics-server-7c557b6b9f-h4hz2            1m           11Mi

Build Kubernetes control plane image with Packer

Steps to prepare single control plane image is quite simple:

  • Prepare Docker and Kubernetes packages and settings
  • Execute kubeadm bootstrap script when EC2 start up first time

One unanswered question is: How to add additional control plane nodes and worker nodes which required tokens and certificates to be preset when joining the cluster?

Continue reading Build Kubernetes control plane image with Packer

Practical guide to Kubernetes Certified Administration exam

I have published practical guide to Kubernetes Certified Administration exam https://github.com/vorozhko/practical-guide-to-kubernetes-administration-exam

Covered topics so far are:

Share your efforts

If your are also working on preparation to Kubernetes Certified Administration exam lets combine our efforts by sharing the practical side of exam.

Disaster recovery of single node Kubernetes control plane

Overview

There are many possible root causes why control plane might become unavailable. Lets review most common scenarios and mitigation steps.

Mitigation steps in this article build around AWS public cloud features, but all popular public cloud offerings have similar functionality.

Apiserver VM shutdown or apiserver crashing

Results

  • unable to stop, update, or start new pods, services, replication controller
  • existing pods and services should continue to work normally, unless they depend on the Kubernetes API
Continue reading Disaster recovery of single node Kubernetes control plane

Thoughts on High available Kubernetes cluster with single control plane node

Why single node control plane?

Benefits are:

  • Monitoring and alerting are simple and on point. It reduce the number of false positive alerts.
  • Setup and maintenance are quick and straightforward. Less complex install process lead to more robust setup.
  • Disaster recovery and recovery documentation are more clear and shorter.
  • Application will continue to work even if Kubernetes control plane is down.
  • Multiple worker nodes and multiple deployment replicas will provide necessary high availability for your applications.

Disadvantages are:

  • Downtime of control plane node make it impossible to change any Kubernetes object. For example to schedule new deployments, update application configuration or to add/remove worker nodes.
  • If worker node goes down during control plane downtime when it will not be able to re-join the cluster after recovery.

Conclusions:

  • If you have a heavy load on Kubernetes API like frequent deployments from many teams then you might consider to use multi control plane setup.
  • If changes to Kubernetes objects are infrequent and your team can tolerate a bit of downtime when single control plane Kubernetes cluster can be great choice.

How to enable minikube kvm2 driver on Ubuntu 18.04

Verify kvm2 support

Confirm virtualization support by CPU 

 egrep -c ‘(svm|vmx)’ /proc/cpuinfo

An output of 1 or more indicate that CPU can use virtualization technology. 

sudo kvm-ok

Output “KVM acceleration can be used. ” indicate that the system has virtualization enabled and KVM can be used.

Continue reading How to enable minikube kvm2 driver on Ubuntu 18.04

How to organize Namespaces in Kubernetes

There are two main objectives:

  1. Users are able to do their job with the highest velocity possible
  2. Users organized by groups in multi tenant setup 

Multi tenancy

Kubernetes namespaces help to setup boundaries between groups of users and applications in a cluster.
To make it more pleasant and secure for your users to work in shared cluster Kubernetes has a number of policies and controls.

Access policies

RBAC primary objective is authorize users and applications to do specific operations in the namespace or in whole cluster. Use RBAC to give your users enough permissions in the namespace, so they can do day to day operations on their own.
Network Policy control how pods can communicate with each other. Use it to firewall traffic between namespaces or inside namespace to critical components like Databases.

Continue reading How to organize Namespaces in Kubernetes

120 Days of AWS EKS in Staging

Felix Georgii wakeboarding at Wake Crane Project in Pula, Croatia on September 25, 2016

My journey with Kubernetes started with Google Kubernetes Engine then one year later with self managed kuberntes and then with migration to Amazon EKS.

EKS as a managed kubernetes cluster is not 100% managed. Core tools didn’t work as expcted. Customers expectation was not aligned with functions provided. Here I have summarized all our experience we gained by running EKS cluster in Staging.

To run EKS you still have to:

  • Prepare network layer: VPC, subnets, firewalls…
  • Install worker nodes
  • Periodically apply security patches on workers nodes
  • Monitor worker nodes health by install node problem detector and monitoring stack
  • Setup security groups and NACLs
  • and more
Continue reading 120 Days of AWS EKS in Staging