Now, when the theory is clear, it's time for a little practice! The Mighty kubectl debug Command So, nothing technically prevents you from, say, performing one-off tasks on behalf of a running Pod by means of ephemeral containers (please don't quote me on that if you decide to try it in prod), but they will be unlikely usable for something more durable. They cannot be restarted, and no ports can be exposed.They can use only already allocated to the Pod resources.They lack guarantees for resources or execution.What prevents you from starting to (ab)use ephemeral containers for running production workloads? Besides common sense, the following limitations: Isn't making Pods mutable against the Kubernetes declarative nature? 🤔 What if new ( somewhat limited) containers could be added to an already running Pod without restarting it? Since Pods are just groups of semi-fused containers and the isolation between containers in a Pod is weakened, such a new container could be used to inspect the other containers in the (acting up) Pod regardless of their state and content.Īnd that's how we get to the idea of an Ephemeral Container - "a special type of container that runs temporarily in an existing Pod to accomplish user-initiated actions such as troubleshooting." Unless we can relax a bit the Pod immutability requirement! Well, probably there is not so many options left. There is, of course, debugging right from a cluster node, but SSH access to the cluster might be off-limits for many of us. So, what other debugging options do we have given the immutability of the Pod's spec?
But even when the debugging tools are available in the container, kubectl exec can be of little help if this container is in a crash loop. Copying debugging tools into running containers on-demand with kubectl cp is cumbersome and not always possible ( it requires a tar executable in the target container). However, this command might be tricky to use if you're not container-savvy.īaking a full-blown Linux userland and debugging tools into production container images makes them inefficient and increases the attack surface. The fastest way to get started is the kubectl debug command. TL DR: Ephemeral containers are indeed great and much needed. So, below are my findings - traditionally sprinkled with a bit of containerization theory and practice 🤓 "This must be something really great!" - thought I and decided to finally give Kubernetes ephemeral containers a try.
#Ephemeral storage kubernetes full
The room was super full - some people were even standing by the doors trying to sneak in.
Last week at KubeCon, there was a talk about Kubernetes ephemeral containers. You can find a Russian translation of this article here.
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