DevOps
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Resolving ImagePullBackOff with Registry Authentication Issues
Encountering an ImagePullBackOff error in Kubernetes can be a frustrating experience, especially when it’s due to a 401 error from a Docker Registry. This guide will walk you through the steps to diagnose and resolve this issue by updating your registry credentials. Diagnosing the ImagePullBackOff Error When a pod fails to pull an image, it…
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Quick-tip: using kubectl when you manage multiple Kubernetes clusters
Kubectl has this great feature of ‘contexts’ which allow you to switch between clusters or even namespaces within a cluster. But how do you go about adding contexts to your version of kubectl? I have used the KUBECONFIG environment variable to specify the location of a custom kubeconfig.yaml file; what I recently discovered was that…
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Kubernetes: Unexpected 502 errors when rolling out a new ReplicaSet
The other day I was working on migrating a platform at a client from Virtual Machine based deployments using Ansible to Container-based deployments using Kubernetes. The whole migration went smooth until we started noticing Bad Gateway (HTTP status 502) errors during load testing. At first we thought that the readiness probes were misconfigured and that…
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How to fix DigitalOcean’s RancherOS disk size
If you, like me, experienced when you start a RancherOS droplet that the disk size is only 8 gigabytes out of the expected 50 gigabytes, then the following two commands may help: sudo growpart /dev/vda 1sudo resize2fs /dev/vda1 Please note that the space between /dev/vda and the 1 in the first command is necessary. This…
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Running websites on a Docker Cluster using Rancher
For my company, Ingewikkeld, we are migrating all our services to run on a series of Droplets at DigitalOcean that together form a cluster of Docker containers. This setup should reduce the costs of all the separate VPS’s that we previously had because Docker hosts automatically fill up the available resources of a host to…
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SSH Tunneling across multiple hosts in Linux
Sometimes you need to communicate with a server (or other device) that is not directly accessible from your own computer. If you can reach this server via another server this is not an issue and can be solved by setting up a SSH Tunnel across your network. An example Let’s start with a example: Computer…
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Human readable memory usage in Linux per process
I like to tune my VPS to use as little memory as possible. Not because I really want to; but because I just don’t have the money to spend on a 2+ GB RAM VPS and I would like to run Jira. In order to do this I keep a close eye on the processes…
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Installing Lotus Notes 8.5 on Kubuntu / Debian Linux KDE
I have recently switched from employer in search of new opportunities, a new challenge and more tech-savy colleagues. After just 2 days I can say that I have found at least the latter two. Although I never expected to find a challenge in the mail system used, namely IBM Lotus Notes. After leaving my previous…