Linux Academy Red Hat Certified Specialist in OpenShift Administration (ex280) Prep Course
This course is specifically designed to prepare students for the Red Hat Certified Specialist in OpenShift Administration (ex280 v3.9) exam, but is also suitable for experienced Linux adminstrators seeking to learn OpenShift cluster administration.
About the Instructors
About the Instructors
Meet Treva Williams, the Training Architect for the ex280 Prep Course! In this video, we introduce the topics that this course will cover, as well as who will benefit the most from taking this course.
About the Course
This course is intermediate-to-advanced and is specifically designed to aid you in preparing for the Red Hat ex280 exam, but can also be used to learn basic OpenShift administration. The course will start off with instructions for setting up a 3-node OpenShift cluster using OKD, the upstream version of OpenShift, for those who wish to follow along on their own workstations, which will be used to practice OpenShift administration tasks included in the exam objectives.
About the Exam
About the Red Hat Certified Specialist in OpenShift Administration
Red Hat Certificate of Specialty in OpenShift Administration Exam ObjectivesOpenShift Container Platform general configuration and management. Understand and use the command line and web console.Create and delete projects.Import, export, and configure Kubernetes resources.Configure persistent registry storage.Examine resources and cluster status.View logs.Troubleshoot common problems. Docker image management. Understand and work with image registries.List images.Load images from archive files.Use image tags.Pull and push images. Users and Policies management. Create and delete users.Modify user passwords.Modify user and group permissions. Application creation and management. Provision persistent application storage.Deploy applications using Source-to-Image (S2I).Use Git to configure applications.Edit and import application templates.Assemble an application from existing components.Deploy multi-container applications.Create containerized services.Create and edit external routes.Secure routes using TLS certificates. Monitoring and Tuning. Install and configure metrics.Limit resource usage.Scale applications to meet increased demand.Control pod placement across cluster nodes.Register for the exam by purchasing an exam license on the Red Hat website
Introduction to OpenShift
OpenShift Container Platform, abbreviated OCP, is a platform as a service (PaaS) offering from Red Hat that brings together Docker and Kubernetes, and provides an API to manage these services. OpenShift has a microservices-based architecture of smaller, decoupled units that work together, running on top of a Kubernetes cluster.
The standard OpenShift cluster is composed of at least one master node (with 2 or more masters in an HA environment) and one or more nodes. Kubernetes manages containerized applications across a set of containers or hosts, and provides deployment mechanisms, application scaling, and maintenance, while Docker packages instantiates and runs containerized applications. OpenShift is a layered system designed to expose underlying Docker-formatted container images and Kubernetes concepts as accurately as possible, with a focus on easy composition of applications by a developer.
About My Setup
3 intel i5 NUCs (1
infra node, one
compute node)32 GB RAM250 - 500 GB SSDs4 CPU coresCentOS 7.5 with custom partitioning
3-5 KVM guests (1 master, 2 nodes, optional registry and NFS storage node)
Minimum resources (Production):16 GB RAM4 (v)CPU40 GB diskRHEL/CentOS x86_64 7.3 or higher
Registry requirements:16 GB RAM2 vCPU15 GB disk + 15 GB unallocated space for Docker storage backendCentOS/RHEL 7.3-7.4 x86_64
Minimum resources (Dev/PoC):4 GB RAM40 GB disk2 vCPU coresCentOS/RHEL 7.3 x86_64 or higher
Registry requirements:4 GB RAM2 (v)CPU15 GB disk + at least 2 GB unallocated space for Docker LVM storageRHEL/CentOS x86_64 7.3 or higher
Or just use hands-on labs ;)
Installing KVM Components
First, verify your CPU supports virtualization:
We should get either the word
grep -E '(vmx|svm)' /proc/cpuinfo
svmin the output, otherwise CPU doesn’t support virtualization. Install KVM and associated packages:
Enable and start
yum install qemu-kvm qemu-img virt-manager libvirt libvirt-python libvirt-client virt-install virt-viewer bridge-utils
Verify that the KVM kernel module is loaded:
systemctl enable --now libvirtd
If you're running CentOS/RHEL 7 minimal,
$ lsmod | grep kvm kvm_intel 162153 0 kvm 525409 1 kvm_intel
virt-managermay not start unless the
x-window-systempackage is installed:
If not running as
yum install "@X Window System" xorg-x11-xauth xorg-x11-fonts-* xorg-x11-utils -y
root(which you shouldn't be), add your
usermod -aG libvirt $USER usermod -aG kvm $USER
The ShadowMan Network
All KVM guests to be used as OpenShift nodes will need to be connected to the same network, which can be achieved by creating a
Bridge in KVM.Start up
virt-managerGo into Menu --> Connection details --> Virtual networksClick
+ to add a networkGive a name
shadowmanSet IP rangeEnable DHCPv4Click NextSkip IPv6 detailsSelect Forward to physical networkFor destination, select your network (eth0, eno1, wlps0, etc)Set Mode to
NATOptional: Set domain name (or leave as
Build the OpenShift Master
Create the OpenShift master in KVM with at least 4 GB of RAM and a 20 GB disk. Use custom partitioning to leave space available for Docker thinpool storage.
OpenShift Compute Nodes
In addition to the OpenShift
master, you will need a
infra node to replicate the environment used for the course. The nodes can be configured using the virt-manager GUI or with the
sudo virt-install --name=compute --file=/var/lib/libvirt/images/infra.qcow2 --file-size=40 --graphics spice --vcpus=1 --ram=4096 --cdrom=/path/to/Downloads/CentOS-7-x86_64-Minimal-1810.iso --network bridge=virbrN --os-type=linux --os-variant=centos7.0
sudo virt-install --name=infra --file=/var/lib/libvirt/images/infra.qcow2 --file-size=40 --graphics spice --vcpus=1 --ram=4096 --cdrom=/path/to/Downloads/CentOS-7-x86_64-Minimal-1810.iso --network bridge=virbrN --os-type=linux --os-variant=centos7.0
Base Packages and Docker Configuration
Once you have created your KVM nodes, you will need to install base packages on all nodes before moving any further. You can quickly and easily run updates and install needed dependencies with the basepkgs.sh bash scriptDownload the
basepkgs.sh script from the
content-openshift-ex280/release-3.9 branch onto all nodes:
Execute the script as
curl -o basepgks.sh https://raw.githubusercontent.com/linuxacademy/content-openshift-ex280/release-3.9/scripts/basepkgs.sh
DNS Resolution for OpenShift
OpenShift requires wildcard DNS resolution in order to resolve OpenShift routes. This can be configured either with DNSMasq, a lightweight internal DNS resolver, or by using a public wildcard DNS resolver like xip.io or nip.io. In this video, I will show you how to configure your OpenShift nodes with both solutions.
Install OKD with openshift-ansible
Both the Enterprise and Upstream versions of OpenShift 3.x are installed using a series of Ansible playbooks included in the
openshift-ansible package. In this video, we will walk through the process of building an inventory specifically for OpenShift, then installing a cluster using
Users, Projects, & Roles
In this video, we discuss managing users, projects, and roles.
Managing projects in OpenShift is very straight-forward. In this video, we will practice creating a new
linuxacademy project, then add an
Managing Resource Quotas
View a list of resources that can be managed with quotas in the OpenShift documentation.
Creating OpenShift Apps
OpenShift applications are, at their most basic level, formed from Linux container technology. These containers, mostly based on Docker-formatted container images, are lightweight basic mechanisms for isolating running processes so that they are limited to interacting with only their designated resources. An image is a binary that includes all of the requirements for running a single container, as well as metadata describing its needs and capabilities. These containers are deployed together in something called a pod - which is one or more containers deployed together on one host, and the smallest compute unit that can be defined, deployed, and managed. These pods have a lifecycle—they are defined, they are assigned to run on a node, then they run until the container(s) exit or they are removed. Pods, depending on policy and exit code, may be removed after exiting, or may be retained in order to enable access to the logs of their containers. OpenShift treats pods as largely immutable, so most changes cannot be made to a pod definition while it is still running. Instead, OpenShift implements changes by terminating the existing pod, then recreating it with the modified configuration, base image(s), or both. OpenShift apps can be created from the dashboard or with CLI of several different components, including but not limited to:Container imagesYAML or JSON templatesSource/binary code
Most app developers create with the hope of reaching as many people as possible. However, that increased demand will create higher load on the app, which is where the need for scaling will come in.
Fortunately, OpenShift applications can be quickly and easily scaled up/down without the added burden of creating or reconfiguring load balancing or other complex networking settings both via the web console and by using Origin clients (oc). OpenShift apps are scaled horizontally—new pods are added to an application and network requests are served using load balancing algorithms with HAProxy. When using oc, the
oc scale command can be run against the
replicaset for an app.
Securing OpenShift Routes
OpenShift container platform uses routes to expose services at a hostname so that external users can access the service in a browser, usually configured with a DNS wildcard entry pointing to the OCP node that is running the router.
Routes can either be unsecured or secured. Secure routes provide ability to use several types of TLS termination to serve SSL certificates to the visitor. Router plug-ins assume they can bind to host ports 80 (HTTP) and 443 (HTTPS), by default. This means that routers must be placed on nodes where those ports are not otherwise in use, or the router must be manually configured to listen to other unoccupied ports in OCP environment variables. Like most OCP services, routes can be configured and managed using YAML templates.
Supported traffic protocols:HTTPHTTPSWebSocketTLS with SNI
Each route consists of a name, limited to 63 characters, that by default follows the format of
Podname-namespace.subdomain.$hostname, a service selector, and an optional security configuration.
Create a standard route by exposing the service attached to a pod:
# oc get svc NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE longhorns ClusterIP 172.30.16.95 <none> 8080/TCP 15s
# oc expose svc/longhorns route "longhorns" exposed
OpenShift is S2I-enabled and can use S2I as one of its build mechanisms (in addition to building Docker images from Dockerfiles, and "custom" builds). OpenShift runs the S2I process inside a special Pod, called a Build Pod, and thus, builds are subject to quotas, limits, resource scheduling, and other aspects of OpenShift. Create a Django app using S2I:
oc new-app centos/python-35-centos7~https://github.com/sclorg/django-ex
Managing Persistent Storage
OpenShift Container Platform leverages the Kubernetes persistent volume (PV) framework to allow administrators to provision persistent storage for a cluster. Using persistent volume claims (PVCs), developers can request PV resources without having specific knowledge of the underlying storage infrastructure.
The Container Registry
The Docker Registry
A container registry is a service for storing and retrieving Docker-formatted container images. A registry contains a collection of one or more image repositories, and each image repository contains one or more tagged images. Docker provides its own registry, the Docker Hub. You can also use private or third-party registries. OpenShift Container Platform can also supply its own internal registry for managing custom container images. The OpenShift Container Registry provides users with a built-in location for application builds to push resulting images, and adds the ability to provision new, on-demand image repositories. The OpenShift Container registry can also deploy as a stand-alone component, either on-prem or in the Cloud, acting solely as a container registry without the build and deployment integration that comes with an integrated OCR.
The OpenShift Container Registry provides users with a built-in location for application builds to push resulting images called
ImageStreams, and adds the ability to provision new, on-demand image repositories.
OpenShift Cluster Metrics
Cluster Metrics with Hawkular
Let’s talk about Metrics in OpenShift. As an OpenShift Container Platform administrator, you can view a cluster’s metrics from all containers and components using the Hawkular Metrics engine plugin. These metrics are also used by horizontal pod autoscalers in order to determine when and how to scale.
Hawkular Metrics can be installed either by adding the
openshift_metrics_install_metrics=True variable to the cluster
inventory or by declaring variables directly on the CLI, like so:
ansible-playbook [-i /path/to/inventory] <OPENSHIFT_ANSIBLE_DIR>/playbooks/openshift-metrics/config.yml -e openshift_metrics_install_metrics=True -e openshift_metrics_hawkular_hostname=hawkular-metrics.example.com -e openshift_metrics_cassandra_storage_type=pv
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