Sometimes when managing multiple kubernetes clusters, you will end up with multiple kubeconfig files. You use kubeconfig to authenticate to the cluster. The default kubeconfig is always placed in ~/.kube/config. In an event that you already have the ~/.kube/config file and you are importing a new cluster, you might need to merge them together.

We use kubeconfig files to organize information about clusters, users, namespaces, and authentication mechanisms. kubectl command-line tool itself, uses kubeconfig files to source the information it needs in order to connect and communicate with the API server of a cluster.

By default, kubectl requires a file named config that lives under $HOME/.kube directory. You can multiple cluster entries in that file or specify additional kubeconfig files by setting the KUBECONFIG environment variable or by setting the --kubeconfig flag.

In this guide, we will assume that we have our default kubeconfig here ~/.kube/config and are importing a new cluster here ~/.kube/new.yml.

Ideally, kubernetes has this feature out of the box. If you supply e.g. export KUBECONFIG="${KUBECONFIG}:config-file-1:config-file-2 it will merge those three files. But it can be cumbersome so we will learn how to combine them into a single file.

To see your configuration, enter this command:

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kubectl config view

Backup the original kubeconfig file

Make a copy of your existing config so you can always fallback to it in case of anything

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cp ~/.kube/config ~/.kube/config.bk

Merge the two config files together into a new config file

Set the KUBECONFIG env variables with a list of kubeconfigs to combine

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export KUBECONFIG=~/.kube/config:~/.kube/new.yml

If you want to see now the current merged configuration that your kubectl is working with, just issue the command:

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kubectl config view

Next flatten the config into one file

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kubectl config view --flatten > /tmp/all-in-one-kubeconfig.yml

Replace your old config with the new merged config

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mv /tmp/all-in-one-kubeconfig.yml ~/.kube/config

Once we have our new kubeconfig, lets set its permissions properly:

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chmod 600 ~/.kube/config

Delete the backup once you confirm everything worked ok

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rm ~/.kube/config.bk

We can now set our context to the new cluster we’ve just provisioned!

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kubectl config use-context $(kubectl config get-contexts --kubeconfig=~/.kube/config --output=name)

You can also verify with this command

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kubectl config get-clusters