A Practical Introduction to Container Terminology

You might think containers seem like a pretty straightforward concept, so why do I need to read about container terminology? In my work as a container technology evangelist, I’ve encountered misuse of container terminology that causes people to stumble on the road to mastering containers. Terms like containers and images are used interchangeably, but there are important conceptual differences. In the world of containers, repository has a different meaning than what you’d expect. Additionally, the landscape for container technologies is larger than just docker. Without a good handle on the terminology, It can be difficult to grasp the key differences between docker and (pick your favorites, CRI-O, rkt, lxc/lxd) or understand what the Open Container Initiative is doing to standardize container technology.

Background

It is deceptively simple to get started with Linux Containers. It takes only a few minutes to install a container engine like docker and run your first commands. Within another few minutes, you are building your first container image and sharing it. Next, you begin the familiar process of architecting a production-like container environment, and have the epiphany that it’s necessary to understand a lot of terminology and technology behind the scenes. Worse, many of the following terms are used interchangeably… often causing quite a bit of confusion for newcomers.

  • Container
  • Image
  • Container Image
  • Image Layer
  • Registry
  • Repository
  • Tag
  • Base Image
  • Platform Image
  • Layer

Understanding the terminology laid out in this technical dictionary will provide you a deeper understanding of the underlying technologies. This will help you and your teams speak the same language and also provide insight into how to better architect your container environment for the goals you have. As an industry and wider community, this deeper understanding will enable us to build new architectures and solutions. Note, this technical dictionary assumes that the reader already has an understanding of how to run containers. If you need a primer, try starting with  A Practical Introduction to Docker Containers on the Red Hat Developer Blog.

Continue reading “A Practical Introduction to Container Terminology”

Share

Red Hat Container Development Kit (CDK) With Nested KVM

Why

If you are like me, you probably prefer to install new and exploratory software in a fresh virtual machine (VM) or container to insulate your laptop/desktop from software pollution (TM). Red Hat Container Development Kit (CDK) relies on virtualization to create a Red Hat Enterprise Linux (RHEL) virtual machine to run OpenShift (based on Kubernetes). Red Hat specifically supports installation of the CDK on Windows, macOS, and RHEL Server, but if you are running Fedora, RHEL Workstation, or even CentOS, you will run into trouble. If you are not running a supported desktop, you can always use a RHEL Server virtual machine, and this tutorial is for you.

Continue reading “Red Hat Container Development Kit (CDK) With Nested KVM”

Share

SnowCamp 2018 Trip Report

Last week, Red Hat was present at the SnowCamp conference in Grenoble, France. The SnowCamp is a technical conference that includes a unique combination of deep dive sessions (universities), technical talks, and a final day on the ski slopes. With around 400 attendees and 70 sessions, this third edition of the SnowCamp was a great opportunity to meet the developers from the Grenoble area, in the most innovative city in the world (Source: Forbes  and Mashable). Red Hatters presented 2 universities and 7 talks covering many projects and products, such as OpenShift, Infinispan, Monitoring, and Containers.
Let’s have a look to them.

Continue reading SnowCamp 2018 Trip Report

Share

Containerizing SQL DB changes with Flyway, Kubernetes, and OpenShift

In DevOps projects, you are sometimes haunted by the practices inherited from the monolithic world. In a previous project, we were checking how to simply apply SQL updates and changes to a relational database management system (RDBMS) database in an OpenShift Cluster.

Micro database schema evolution patterns are perfectly described by Edson Yanaga in his brilliant free book: Migrating to Microservice Databases: From Relational Monolith to Distributed Data.  A video presentation of these patterns is also available on youtube.

In this blog post series we will show a simple approach to implement the described patterns in your Continuous Integration and Continuous Delivery (CI/CD) pipelines on OpenShift. The series is split in two parts:

  • This post shows how to handle SQL update automation using Flyway, Dockerfiles, and Kubernetes on OpenShift.
  • A future post will showcase application migration patterns, including database migration stages using OpenShift Jenkins2 pipelines.

Continue reading “Containerizing SQL DB changes with Flyway, Kubernetes, and OpenShift”

Share

Flexible Images or Using S2I for Image Configuration

Container images usually come with pre-defined tools or services with minimal or limited possibilities of further configuration. This brought us into a way of thinking of how to provide images that contain reasonable default settings but are, at the same time, easy to extend. And to make it more fun, this would be possible to achieve both on a single Linux host and in an orchestrated OpenShift environment.

Source-to-image (S2I) has been introduced three years ago to allow developers to build containerized applications by simply providing source code as an input. So why couldn’t we use it to make configuration files as an input instead? We can, of course!

Continue reading “Flexible Images or Using S2I for Image Configuration”

Share

Wiping the Slate Clean with the OpenShift Container Platform

With traditional virtualized infrastructure or Infrastructure-as-a-Service, it is common practice to regularly refresh instances back to a known good state. This provides confidence that the application workloads have the correct runtime configuration, no deltas are being introduced, and they can be relied upon to provide value for the business. In these cases, you might use tools such as Ansible or Jenkins, but when we move our application workloads to containers running on OpenShift Container Platform, we can use native tools provided by that platform to achieve the same result.

Continue reading “Wiping the Slate Clean with the OpenShift Container Platform”

Share