kubectl proxy#

Learned about this today as a way of accessing the Kubernetes REST API.

Assuming you have kubectl setup and authorized against a cluster (I’m using DigitalOcean K8S) you can start a localhost proxy for talking to the API server in the cluster like this:

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kubectl proxy --port 9000

This starts a proxy running on localhost port 9000 which can be used to make authenticated API calls to the cluster. The authentication wrapper (which I think defaults to client certificates) is added automatically, so you can just hit http://localhost:9000/ using curl.

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curl localhost:9000
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{
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  "paths": [
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    "/.well-known/openid-configuration",
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    "/api",
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    "/api/v1",
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    "/apis",
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    "/apis/",
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    "/apis/admissionregistration.k8s.io",
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    "/apis/admissionregistration.k8s.io/v1",
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    "/apis/admissionregistration.k8s.io/v1beta1",
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    "/apis/apiextensions.k8s.io",
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...

Absolutely everything in Kubernetes is exposed via the API. Hitting the homepage, as above, shows a list of API paths. Then you can do things like this:

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% # List nodes in the cluster
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% curl localhost:9000/api/v1/nodes
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{
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  "kind": "NodeList",
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  "apiVersion": "v1",
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  "metadata": {
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    "resourceVersion": "18429049"
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  },
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  "items": [
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    {
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      "metadata": {
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        "name": "..."
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% # List pods (effectively containers) in the cluster:
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% curl localhost:9000/api/v1/pods
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{
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  "kind": "PodList",
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  "apiVersion": "v1",
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  "metadata": {
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    "resourceVersion": "18429226"
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  },
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  "items": [
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    {
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      "metadata": {
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        "name": "alpaca-prod",
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        "namespace": "default",
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        "uid": "50b03bf7-c46d-4ebb-ab93-df089940fa9c",
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        "resourceVersion": "1207774",
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        "creationTimestamp": "2021-10-31T21:18:08Z",
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        "labels": {
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% # Show Kubernetes version
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% curl localhost:9000/version
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{
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  "major": "1",
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  "minor": "21",
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  "gitVersion": "v1.21.5",
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  "gitCommit": "aea7bbadd2fc0cd689de94a54e5b7b758869d691",
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  "gitTreeState": "clean",
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  "buildDate": "2021-09-15T21:04:16Z",
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  "goVersion": "go1.16.8",
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  "compiler": "gc",
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  "platform": "linux/amd64"
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}