Silly Kubectl Trick #1: EXPLAIN YOURSELF, KUBERNETES!
Is a container's set of mounted volumes an array? An object? With explain, I don't have to remember.
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Join For FreeTo 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?
kubectl
knows.
The online Kubernetes API Reference Documentation site is great, but kubectl
can help us out here with its kubectl explain
command:
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:
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$ kubectl explain statefulsets | head -n2
KIND: StatefulSet
VERSION: apps/v1
Did you know that the keys in a ConfigMap's data
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
does:
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$ 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 explain
, I don't have to remember:
x
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 pod.spec.containers
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!
Check Out the Video!
If you like that, check out the accompanying video, which goes into a bit more depth. Plus, you get to listen to the dulcet tones of me, your author.
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