Kubernetes cluster configuration merger

/kubeconfig/add-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. Then you provision a new cluster, you get your shiny new cluster configuration file and then you have to copy over those entries to your main config file.

This script does that automatically. You just provide the name of the new context you want to create for this configuration and it takes care of adding the entries to your kubectl config file.

The name of the new context is the only mandatory argument. Then you can pass up to two additional arguments:

The name of the configuration file that you want to copy to your main config file. Default: admin.conf because that’s what I mostly get.
The name of the destination kubectl config file. I decided to add this third argument just in case you have your config file elsewhere or you want to do some testing. Default: ~/.kube/config.

Finally, for editing 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
#
# add-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="$1"
kcfile="${2-admin.conf}"
kubeconfig=${3-~/.kube/config}

if [[ ! -f "$kcfile" ]]; then
	echo "$0: missing cluster config file" >&2
	exit 1
fi

if [[ ! -f "$kubeconfig" ]]; then
	mkdir -p "$(cd "$(dirname "$kubeconfig")"; pwd)"
fi

kctemp="$(< "$kcfile")"

# First, clean the cluster config file
if [[ -f "$kubeconfig" ]]; then
	kctemp="$("$yq" eval "del(.[\"apiVersion\", \"current-context\", \"kind\", \"preferences\"])" - <<< "$kctemp")"
fi

# Set the context name for all entries
kcexpr="$(printf '"%s" as $contextname |\n' "$context_name"; cat <<-'EOF'
. * {
	"contexts": [.contexts[] | (.context | (.cluster,.user),.name) |= $contextname],
	"users": [.users[] | .name |= $contextname],
	"clusters": [.clusters[] | .name |= $contextname]
}
EOF
)"
kctemp="$("$yq" eval "$kcexpr" - <<< "$kctemp")"

# Then, merge the cleaned config to the kubeconfig file
if [[ -f "$kubeconfig" ]]; then
	kcexpr="$(printf '"%s" as $contextname |\n' "$context_name"; cat <<-'EOF'
	(
		select(fileIndex == 0) |
		del(.["contexts", "users", "clusters"][] | select(.name == $contextname))
	) *+d select(fileIndex == 1)
	EOF
	)"
	"$yq" -i eval-all "$kcexpr" "$kubeconfig" - <<< "$kctemp"
else
	cat > "$kubeconfig" <<< "$kctemp"
fi

~/.eth0/

This is my code. There is a lot like it, but this is mine.

Kubernetes cluster configuration merger

/kubeconfig/add-kubeconfig.sh