R&D at Stark & Wayne, finding software solutions to customer problems and changing them into executable best practices.
To say that Kubernetes uses a bit of YAML is like saying that a few people put some of their code on GitHub – accurate, but severely understated.
Kubernetes uses a LOT of YAML. It takes over 50 lines of YAML to get a namespace with a single-container deployment with a service, no volumes, no secrets, and no configuration.
Keeping all that syntax straight can be daunting. Is that property a string or can it be a number? Does that collection get set as a map or a list? Who knows?
The online Kubernetes API Reference Documentation site is great, but
can help us out here with its
kubectl explain pod.spec.containers kubectl explain deployments.metadata kubectl explain secret.data
Each of these invocations will spit out documentation about the specified bits of Kubernetes resource YAML. I use it all the time to remember which API group/version a given object type exists in:
$ kubectl explain statefulsets | head -n2 KIND: StatefulSet VERSION: apps/v1
Did you know that the keys in a ConfigMap’s
attribute must follow a strict format? Or that non-UTF-8 configuration values are supposed to go in a different top-level attribute altogether?
$ kubectl explain configmap.data KIND: ConfigMap VERSION: v1 FIELD: data <map[string]string> DESCRIPTION: Data contains the configuration data. Each key must consist of alphanumeric characters, '-', '_' or '.'. Values with non-UTF-8 byte sequences must use the BinaryData field. The keys stored in Data must not overlap with the keys in the BinaryData field, this is enforced during validation process.
I have a tough time remembering what things are specified as lists, and what things are specified as keyed maps. Is a container’s set of mounted volumes an array? An object? With
, I no longer have to remember:
kubectl explain pod.spec.containers.volumeMounts KIND: Pod VERSION: v1 RESOURCE: volumeMounts <Object> DESCRIPTION: Pod volumes to mount into the container's filesystem. Cannot be updated. VolumeMount describes a mounting of a Volume within a container. ... etc. ...
Note: Even though
is a list, you don’t have to worry about that when referencing through it to its sub-fields. This is in contrast to JSON path expressions and Go Templates. It’s so handy (and transparent!) that I had to point this out, explicitly!
If you like that, check out the accompanying video which goes into a bit more depth:
The next tip will help you figure out what images you’re running in production.
Previously published at https://www.starkandwayne.com/blog/silly-kubectl-trick-1-explain-yourself-kubernetes/
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