For the purposes of this guide, I'll refer to the two clusters are "source" and "destination". We want to copy a secret from our "source" cluster to our "destination" cluster.
So first, ensure you're authenticated with your source cluster.
kubectl config current-context
This should show the name of the context configured to access your source cluster.
Now export the secret, and store the secret config data in a file.
kubectl get secret my-secret-name --export -o yaml > my-secret-name.yaml
Now, you can import the secret into the new cluster. So go ahead and authenticate with the destination cluster, and simply apply the config file you just exported.
kubectl apply -f my-secret-name.yaml
Now confirm your secret was created properly.
kubectl get secret
This should show your newly created secret.
Now, a quick note on security. There are security risks associated with storing sensitive information on your file system (even if the file is deleted). In any case, you'll want to delete the file that was used to temporarily store the secret data, and only use this method if you understand the risks and are happy to accept them.
The first two steps were broken out, but can be combined into a single command.
First you'll need to get the context names for your two clusters. This command will help:
kubectl config get-contexts
Now you can run:
kubectl get secret my-secret-name --context source_context --export -o yaml | kubectl apply --context destination_context -f -
Hopefully you recognize some of the component parts of this script. We're skipping the part where we export the config to a file, and instead piping the config into
kubectl apply. Notice that we can set the context for each
kubectl command, this allows us to send data from one cluster to another. Beautiful!