terraform-hcloud-kube-hetzner/docs/ssh.md

Kube-Hetzner requires you to have a recent version of OpenSSH (>=6.5) installed on your client, and the use of a key-pair generated with either of the following algorithms:

• ssh-ed25519 (preferred, and most simple to use without passphrase)
• rsa-sha2-512
• rsa-sha2-256

If your key-pair is of the ssh-ed25519 sort, and without of passphrase, you do not need to do anything else. Just set public_key and private_key to their respective path values in your terraform.tfvars.

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Otherwise, for a key-pair with passphrase or a device like a Yubikey, make sure you have have an SSH agent running and your key is loaded with:

eval ssh-agent $SHELL
ssh-add ~/.ssh/my_private-key_id

Verify it is loaded with:

ssh-add -l

Then set private_key = null in your terraform.tfvars, as it will be read from the ssh-agent automatically.