CentOS 7

The deployment process involves several steps:

1. Install Docker
2. Configure an insecure registry
3. Allow ports on the firewall
4. Download the OpenShift client utility
5. Start a cluster

Let's study these steps in detail:

1. Docker installation: This doesn't involve anything special, and was described in previous chapters. The following commands must be run under the root account:

$ sudo -i
# sudo yum -y install docker
# systemctl enable docker

2. Configuring an insecure registry: This is required to be able to use an internal Docker registry, which comes with OpenShift installation. If this is not configured, oc cluster up will fail.

To allow for an insecure OpenShift registry, run the following commands under the root user:

# cat << EOF >/etc/docker/daemon.json
{
   "insecure-registries": [
     "172.30.0.0/16"
   ]
}
EOF

# systemctl start docker

3. Configuring the firewall: The default firewall configuration doesn't enable all of the ports required for an OpenShift cluster. You need to adjust the settings using firewall-cmd

This can be achieved through the following snippet:

# firewall-cmd --permanent --new-zone dockerc
# firewall-cmd --permanent --zone dockerc --add-source 172.17.0.0/16
# firewall-cmd --permanent --zone dockerc --add-port 8443/tcp
# firewall-cmd --permanent --zone dockerc --add-port 53/udp
# firewall-cmd --permanent --zone dockerc --add-port 8053/udp
# firewall-cmd --reload

4. Downloading the oc utility: The OpenShift client utility named oc is available in standard repositories; however, it is possible to download the utility from https://github.com/openshift/origin/releases. We would recommend using the standard CentOS repositories:

# yum -y install centos-release-openshift-origin39
# yum -y install origin-clients

5. Starting an OpenShift cluster: Once all of the prerequisites are met, you will be able to start the cluster by running oc cluster up. The command will download all of the required Docker images from public repositories, and then run all of the required containers:

# oc cluster up --version=v3.9.0
Starting OpenShift using openshift/origin:v3.9.0 ...
...
output truncated for brevity
...
OpenShift server started.

The server is accessible via web console at:
    https://127.0.0.1:8443

You are logged in as:
    User: developer
    Password: <any value>

To login as administrator:
    oc login -u system:admin

As you can see, oc cluster up deployed a ready-to-use, one-node OpenShift environment.

By default, this OpenShift environment was configured to listen on the loopback interface (127.0.0.1). This means that you may connect to the cluster using https://127.0.0.1:8443. This behavior can be changed by adding special parameters, such as --public-hostname=. A full list of available options can be shown by using the following command:

# oc cluster up --help

6. Verification: Once the cluster has deployed, you can verify that it is ready to use. The default OpenShift configuration points you to an unprivileged user, named developer. You may raise your permissions by using the following commands:

# oc login -u system:admin
Logged into "https://127.0.0.1:8443" as "system:admin" using existing credentials.

You have access to the following projects and can switch between them with 'oc project <projectname>':

    default
    kube-public
    kube-system
  * myproject
    openshift
    openshift-infra
    openshift-node

Using project "myproject".

Once you have admin access rights, you can verify the node configuration with oc get node:

# oc get node
NAME      STATUS  AGE     VERSION
localhost Ready   9m       v1.7.6+a08f5eeb62

7. Shutting down: Once an oc cluster up environment has deployed, it can be shut down with oc cluster down.