Building container images for OpenNMS

The previous article described how you can build and compile OpenNMS Horizon from source. This section explains how you build container images (OCI) from the source artifacts.

Deploy base image as foundation

Running OpenNMS Horizon core, Minion, or Sentinels in a container requires shared components. Some of them are a) the JDK base image, b) some useful tools, and c) JICMP, and JICMP6.

The JDK is shared with Core, Minion, and Sentinel. JICMP, and JICMP6 are required for Core and Minion. To manage these dependencies, we have a deploy-base image created which covers the main requirements running the Core, Minion, and Sentinel server processes. Getting an efficient size was a goal and a multi-stage build approach was chosen to address it. The fist

Hello Containerlab with Orbstack

I still remember signing up on DockerHub 11 years ago. Learning how to build container images on real world projects is definitely a plus. Having a software and some use cases in the back of your mind, helps you to achieve things quicker and with some purpose. I’ve started to work with containerlab to build some network test environments mainly for three use cases:

• Layer 2 network topologies for network monitoring tests using LLDP, CDP and Bridge-MIB
• Routing topologies with protocols like BGP, OSPF or IS-IS in general
• Some vendor specific network gear for monitoring with SNMP and streaming telemetry

Playing with OpenNMS from this perspective opens some use cases around Netflow, IPFIX, BGP monitoring, and SNMP in general. I was using Docker4Mac for a very long time. At some point in time I have switched to colima which was slim and easy to use. With switching to ARM on my Mac it got a bit more complicated.

Mirroring a container registry

I was working on an article How to run an air gap installation of OpenNMS Horizon on Rocky Linux. I ran into a similar use case and it was not about RPMs or DEB packages, it was all about container images and registries. My question was, how can I get “all” container images into a private registry from DockerHub? Getting your hands dirty with a private registry is something I’ve described in Running a private container registry for testing. Here is a short how-to on how I did it for my future self or anyone else with a similar question.

Running a private container registry for testing

When I signed up for my DockerHub account in 2013, I never thought sooner than later everything ends up in a container image as it is today. DockerHub was the first public free as in free beer registry to distribute your container images. Containers are now everywhere, and DockerHub, a corporate entity running and funding DockerHub, introduced usage limits for the free tier and started commercializing its registry service. I need to play with software in a micro-service architecture on a platform like Kubernetes, and these limits can be daunting.

Containers and Capabilities

I have to work with container images from time to time, and sometimes I need to do networking stuff. Of course, you want to do this as an unprivileged user. Especially when you mix and match with Docker or Kubernetes, it gets sometimes a bit tricky and a lot of people in our community including myself struggled on this part. To document it for my future-self and the ones interested – here is my scenario. I need regularly two things when I run OpenNMS tools in containers:

OpenNMS Horizon, Docker, Traefik and Let's Encrypt

I work from home for over 6 years now and especially when you like networking, want to get stuff up and running and breaking it - you start looking around :) You’ve heard about k8s, k{0,3}s or Microk8s but you don’t want to use it to run your private blog and you find yourself in a spot where the benefits running stuff in containers justify the pain - this article might be something for you :)