How to merge Kubernetes kubectl config files

Sometimes when working with a new Kubernetes cluster you will be given a config file to use when authenticating with the cluster. This file should be placed at ~/.kube/config. However you may already have an existing config file at that location and you need to merge them together.

Here is a quick command you can run to merge your two config files.

# Make a copy of your existing config
$ cp ~/.kube/config ~/.kube/config.bak

# Merge the two config files together into a new config file
$ KUBECONFIG=~/.kube/config:/path/to/new/config kubectl config view --flatten > /tmp/config

# Replace your old config with the new merged config
$ mv /tmp/config ~/.kube/config

# (optional) Delete the backup once you confirm everything worked ok
$ rm ~/.kube/config.bak

Here is all of that (except the cleanup) as a one-liner.

$ cp ~/.kube/config ~/.kube/config.bak && KUBECONFIG=~/.kube/config:/path/to/new/config kubectl config view --flatten > /tmp/config && mv /tmp/config ~/.kube/config