Getting started with OpenShift

OpenShift is Red Hat’s PaaS (Platform-as-a-Service) that allow developers to quickly develop, host, and scale applications in cloud. Based on top of Docker containers and the Kubernetes container cluster manager, OpenShift adds developer and operational centric tools to enable rapid application development, easy deployment and scaling, and long-term lifecycle maintenance for small and large teams and applications.

There are a couple of ways by which you can setup your OpenShift cluster like minishift , oc cluster up. We will be using oc cluster up for this blog.

Setting up single node Openshift cluster using `oc cluster up`

Install docker-daemon on your machine

$ sudo dnf install -y docker engine

Enable docker service

$ sudo systemctl enable docker.service

Start the docker daemon

$ sudo systemctl start docker

To run docker without sudo add user to docker group and reboot the system

    $ sudo gpasswd -a <user> docker
    $ init 6

Configure the Docker daemon with an insecure registry parameter of 172.30.0.0/16 Edit your /etc/sysconfig/docker file and add the following line

     $ INSECURE_REGISTRY='--insecure-registry 172.30.0.0/16' `
     $ sudo systemctl enable docker.service

NOTE: We can run oc cluster up without the insecure registry by using --skip-registry-flag=true flag.

Start OpenShift single node cluster

     $ oc cluster up
    -- Checking OpenShift client ... OK
    -- Checking Docker client ... OK
    -- Checking Docker version ... OK
    -- Checking for existing OpenShift container ... OK
    -- Checking for openshift/origin:v1.5.0-alpha.0 image ... OK
    -- Checking for available ports ... OK
    -- Checking type of volume mount ... 
       Using nsenter mounter for OpenShift volumes
    -- Creating host directories ... OK
    -- Finding server IP ... 
       Using 192.168.121.96 as the server IP
    -- Starting OpenShift container ... 
       Creating initial OpenShift configuration
       Starting OpenShift using container 'origin'
       Waiting for API server to start listening
       OpenShift server started
    -- Adding default OAuthClient redirect URIs ... OK
    -- Installing registry ... OK
    -- Installing router ... OK
    -- Importing image streams ... OK
    -- Importing templates ... OK
    -- Login to server ... OK
    -- Creating initial project "myproject" ... OK
    -- Removing temporary directory ... OK
    -- Server Information ... 
       OpenShift server started.
       The server is accessible via web console at:
           https://192.168.121.96:8443
    
       You are logged in as:
           User:     developer
           Password: developer
    
       To login as administrator:
           oc login -u system:admin

This will start you single node OpenShift cluster on your system.

Deplyoing application on OpenShift

We will deploy guestbook application to our single node cluster, using the docker-compose file. For creating the OpenShift artifacts from Dockerfile we will you Kompose

   $ oc login
   Authentication required for https://192.168.121.96:8443 (openshift)
   Username: admin
   Password: 
   Login successful.
   
   You don't have any projects. You can try to create a new project, by running
   
       oc new-project <projectname>

Create new project

    $ oc new-project guestbook
    Now using project "guestbook" on server "https://192.168.121.96:8443".
    
    You can add applications to this project with the 'new-app' command. For example, try:
    
        oc new-app centos/ruby-22-centos7~https://github.com/openshift/ruby-ex.git
    
    to build a new example application in Ruby.

We need to change the security context in OpenShift since by default OpenShift doesn’t allows to run container with root access. We need to login with OpenShift administrator to make the changes.

    $ oc login -u system:admin
    $ oc edit scc restricted

Change the runAsUser strategy to RunAsAny.

$ oc login -u developer

We can now see the project in the web console.

Create OpenShift Artifacts from docker-compose file.

    $ kompose -f docker-compose.yml --provider=openshift convert -y
    INFO[0000] file "frontend-service.yaml" created         
    INFO[0000] file "redis-master-service.yaml" created     
    INFO[0000] file "redis-slave-service.yaml" created      
    INFO[0000] file "frontend-deploymentconfig.yaml" created 
    INFO[0000] file "frontend-imagestream.yaml" created     
    INFO[0000] file "redis-master-deploymentconfig.yaml" created 
    INFO[0000] file "redis-master-imagestream.yaml" created 
    INFO[0000] file "redis-slave-deploymentconfig.yaml" created 
    INFO[0000] file "redis-slave-imagestream.yaml" created

Create a folder and move all the generated files to that folder

   $ mkdir guestbook
   $ mv frontend-* guestbook
   $ mv redis-* guestbook

Deploy the application

   $ oc create -f guestbook/
    deploymentconfig "frontend" created
    imagestream "frontend" created
    service "frontend" created
    deploymentconfig "redis-master" created
    imagestream "redis-master" created
    service "redis-master" created
    deploymentconfig "redis-slave" created
    imagestream "redis-slave" created
    service "redis-slave" created

Your application has been deployed to OpenShift, for details

    $ oc get dc,svc,is,pvc,pods
    NAME              REVISION   DESIRED   CURRENT   TRIGGERED BY
    dc/frontend       1          1         0         config,image(frontend:v4)
    dc/redis-master   1          1         0         config,image(redis-master:e2e)
    dc/redis-slave    0          1         0         config,image(redis-slave:v1)
    
    NAME               CLUSTER-IP      EXTERNAL-IP   PORT(S)    AGE
    svc/frontend       172.30.10.147   <none>        80/TCP     40s
    svc/redis-master   172.30.8.180    <none>        6379/TCP   39s
    svc/redis-slave    172.30.28.207   <none>        6379/TCP   39s
    
    NAME              DOCKER REPO                                 TAGS      UPDATED
    is/frontend       172.30.44.119:5000/guestbook/frontend       v4        25 seconds ago
    is/redis-master   172.30.44.119:5000/guestbook/redis-master   e2e       24 seconds ago
    is/redis-slave    172.30.44.119:5000/guestbook/redis-slave    v1        
    
    NAME                      READY     STATUS    RESTARTS   AGE
    po/frontend-1-y9bca       1/1       Running   0          2m
    po/redis-master-1-meqjr   1/1       Running   0          2m

Web console of the application being deployed

We now need to expose the service so that application to make it accessible to public.

   $ oc get svc
    NAME           CLUSTER-IP      EXTERNAL-IP   PORT(S)    AGE
    frontend       172.30.10.147   <none>        80/TCP     12m
    redis-master   172.30.8.180    <none>        6379/TCP   12m
    redis-slave    172.30.28.207   <none>        6379/TCP   12m

   $ oc expose svc frontend
    route "frontend" exposed
    
   $ oc get route
    NAME       HOST/PORT                                  PATH      SERVICES   PORT      TERMINATION
    frontend   frontend-guestbook.192.168.121.96.xip.io             frontend   80

Access the application.

We have successfully deployed the guestbook application on OpenShift.

OpenShift Cheat Sheet.

$ oc type

It will give you a quick summary of different conceptual types and definitions user in OpenShift. Also check out oc help and oc --help to see description and examples and learn how to use the commands.

Setting up single node Openshift cluster using oc cluster up