Problem scenario
You are trying to create a virtual router in OpenShift.  When you run the command “oc adm router goodname” you get this error:

“error: router could not be created; could not retrieve list of security constraints to verify service account “router”: securitycontextconstraints.security.openshift.io is forbidden: User “jdoe” cannot list securitycontextconstraints.security.openshift.io at the cluster scope: User “jdoe” cannot list all securitycontextconstraints.security.openshift.io in the cluster”

What should you do?

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Question
What are the differences between Kubernetes and OpenShift?

Answer

• OpenShift was built by Red Hat.  OpenShift did not originally use Kubernetes (OpenShift blog).  Kubernetes was built at Google.
• Kubernetes is open source whereas OpenShift usually costs money.  There are different types of OpenShift (e.g., OpenShift Online, OpenShift Enterprise etc.).
• You use “oc” (OpenShift Client) commands with OpenShift that are often identical to “kubectl” commands in the options that they support. 

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Problem scenario
You installed OpenShift.  You want to determine which version you are using.  What do you do?

Solution
Run this command:  oc version

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Problem scenario
OpenShift has projects unlike Kubernetes.  You are using OpenShift.  You are not sure which project you are working in.  How do you find out its name?

Solution
Run this command:  oc project

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Problem scenario
You want to use OpenShift as opposed to Kubernetes.  How do you deploy OpenShift to try it out?

Solution
1.  Install Docker on Linux.  We recommend you use a RedHat OS.  The hardware requirements are not that high if you are just testing it for development and/or learning purposes.  For directions on how to install Docker on a RedHat distribution of Linux, see this 

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Problem scenario
You want to install kube-proxy, kube-apiserver, kube-controller-manager, and kube-scheduler on a Linux server.  You want to be able to run these commands. How do you do this?

Solution

Prerequisite
This requires the Linux server to have access to the internet.

Procedures
1.  Download the first tar ball.

cd /usr/bin
sudo wget https://github.com/kubernetes/kubernetes/releases/download/v1.8.6/kubernetes.tar.gz
# To get the latest version,

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Problem scenario
You want to install kubelet, kubeadm, kubectl, and etcd on an Ubuntu server.  How do you do this?

Solution
1.  Run these five commands:

sudo apt-get -y update
sudo apt -y install docker.io
sudo su –
curl -s https://packages.cloud.google.com/apt/doc/apt-key.gpg | apt-key add –
exit

2.  Use either Method A or Method B.

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