K8s

Sometimes we need to run a container to do a specific task, and when its completed, we want it to quit. Many containers are deployed and continuously run, such as a web server. But other times we want to accomplish a single task and then quit. This is where a Job is a good choice. Jobs and CronJobs - The Theory Perhaps, we need to run a batch process on demand. Maybe we built an automation routine for something and want to kick it off through the use of a container. We can do this by submitting a job to the Kubernetes API. Kubernetes will run the job to completion and then quit. ...

One of my least favorite parts of computers is dealing with certificate creation. In fact, ya know those tweets about what you’d tweet if you were kidnapped and didn’t want to tip off the kidnapers? Yeah, I’d tweet about how I love working with certificates. They are just not a fun thing for me. So when I found a new project where I needed certificates created, I was not really excited. ...

Securing and hardening our Kubernetes clusters is a must do activity. We need to remember that containers are still just processes running on the host machines. Sometimes these processes can get more privileges on the Kubernetes node than they should, if you don’t properly setup some pod security. This post explains how this could be done for your own clusters. Pod Security Policies - The Theory Pod Security policies are designed to limit what can be run on a Kubernetes cluster. Typical things that you might want to limit are: pods that have privileged access, pods with access to the host network, and pods that have access to the host processes just to name a few. Remember that a container isn’t as isolated as a VM so we should take care to ensure our containers aren’t adversely affecting our nodes’s health and security. ...

There are a myraid of ways to deploy Kubernetes clusters these days. Kubernetes the Hard Way Cluster API Kubeadm Kubespray kops Those are just a few of the ways and I’m sure you’ll have a favorite. But for the work I’ve been doing lately, I don’t want to spend a bunch of time cloning repos, updating configs, running ansible scripts and the like, just to get another clean kubernetes cluster in my lab to break. So, I took the individual parts of a Kubernetes build and created a list of ordered jobs in my Jenkins server. ...

Deploying Kubernetes clusters may be the biggest hurdle in learning Kubernetes and one of the challenges in managing Kubernetes. ClusterAPI is a project designed to ease this burden and make the management and deployment of Kubernetes clusters simpler. The Cluster API is a Kubernetes project to bring declarative, Kubernetes-style APIs to cluster creation, configuration, and management. It provides optional, additive functionality on top of core Kubernetes. kubernetes-sigs/cluster-api This post is designed to dive into ClusterAPI to investigate how it works, and how you can use it. ...

In the traditional server world, we’ve taken great lengths to ensure that we can micro-segment our servers instead of relying on a few select firewalls at strategically defined chokepoints. What do we do in the container world though? This is where network policies come into play. Network Policies - The Theory In a default deployment of a Kubernetes cluster, all of the pods deployed on the nodes can communicate with each other. Some security folks might not like to hear that, but never fear, we have ways to limit the communications between pods and they’re called network policies. ...

I’m not going to lie to you, as of the time of this writing, maybe the biggest hurdle to learning Kubernetes is getting a cluster stood up. Right now there are a myriad of ways so stand up a cluster, but none of them are really straight forward yet. If you’re interested in learning how Kubernetes works, and just want to setup a basic cluster to poke around in, this post is for you. ...

If you’ve just gotten started with Kubernetes, you might be curious to know how the desired state is achieved? Think about it, you pass a YAML file to the API server and magically stuff happens. Not only that, but when disaster strikes (e.g. pod crashes) Kubernetes also makes it right again so that it matches the desired state. The mechanism that allows for Kubernetes to enforce this desired state is the control loop. The basics of this are pretty simple. A control loop can be though of in three stages. ...

I don’t know about you, but I learn things best when I have a visual to reference. Many of my posts in this blog are purposefully built with visuals, not only because I think its helpful for the readers to “get the picture”, but also because that’s how I learn. Kubernetes can feel like a daunting technology to start learning, especially since you’ll be working with code and the command line for virtually all of it. That can be a scary proposition to an operations person who is trying to break into something brand new. But last week I was introduced to a project from VMware called Octant, that helps visualize whats actually going on in our Kubernetes cluster. ...

DaemonSets can be a really useful tool for managing the health and operation of the pods within a Kubernetes cluster. In this post we’ll explore a use case for a DaemonSet, why we need them, and an example in the lab. DaemonSets - The Theory DaemonSets are actually pretty easy to explain. A DaemonSet is a Kubernetes construct that ensures a pod is running on every node (where eligible) in a cluster. This means that if we were to create a DaemonSet on our six node cluster (3 master, 3 workers), the DaemonSet would schedule the defined pods on each of the nodes for a total of six pods. Now, this assumes there are either no taints on the nodes, or there are tolerations on the DaemonSets. ...