Kubernetes cluster configuration extractor

/kubeconfig/extract-kubeconfig.sh

If you tend to work with lots of Kubernetes clusters, you’ll probably have a ~/.kube/config file full of cluster configurations, users and contexts. Maybe at some point you have to extract entries for one particular context, for example to share a cluster configuration with someone.

This script does that automatically. You just provide the name of the new context you want to extract for this configuration and it outputs the minimal YAML contents for a usable kubectl configuration.

The name of the context is the only mandatory argument. Then you can pass up an additional argument, which is the path to your kubectl configuration file. Default: ~/.kube/config.

Finally, for extracting and merging the YAML entries, this script makes use of the yq tool from Mike Farah. You must download the single binary from the releases page in GitHub and put it somewhere in your $PATH. Don’t confuse it with the yq Python package: that’s just a wrapper around jq and works in a completely different way.

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#!/usr/bin/env bash
#
# extract-kubeconfig.sh
# Copyright 2020 eth0 <ethernet.zero@gmail.com>
#
# This work is free. You can redistribute it and/or modify it under the terms of
# the ISC License.
#

yq="$(command -v yq)"

if [[ -z "$yq" ]]; then
	echo "$0: you need the yq tool, download it from https://github.com/mikefarah/yq/releases" >&2
	exit 1
fi

if [[ ! "$1" ]]; then
	echo "$0: you must specify a context name" >&2
	exit 1
fi

context_name="$1"
kubeconfig=${2-~/.kube/config}

if [[ ! -f "$kubeconfig" ]]; then
	echo "$0: $kubeconfig doesn't exist" >&2
	exit 1
fi

kcexpr="$(printf '"%s" as $contextname |\n' "$context_name"; cat <<-'EOF'
(.contexts[] | select(.name == $contextname).context) as $context |
{
	"apiVersion": "v1",
	"kind": "Config",
	"preferences": {},
	"current-context": $contextname,
	"contexts": [{"name": $contextname, "context": $context}],
	"users": [.users[] | select(.name == $context.user)],
	"clusters": [.clusters[] | select(.name == $context.cluster)]
}
EOF
)"

yq eval "$kcexpr" "$kubeconfig"