Exhausted Available Authentication Methods Error with RSA Key (SSH)

If you’re encountering the “Exhausted available authentication methods” error when using an RSA key on an Ubuntu 22.04 or newer server, it’s a sign that your RSA key is outdated and potentially insecure. This guide will help you resolve the issue by upgrading to a modern and secure ed25519 keypair.

Error: Exhausted available authentication methods

When attempting to SSH into your server with the RSA key, you might see the following error message:

Exhausted available authentication methods

To resolve this issue and enhance your server’s security, follow these steps:

1. Generate a New ed25519 Keypair:

On your server, open a terminal and generate a new ed25519 keypair using the ssh-keygen command:

ssh-keygen -t ed25519
You can accept the default location for the key files or specify a custom location.

2. Add the New Public Key to Authorized Keys:

Copy the newly generated public key to your server’s ~/.ssh/authorized_keys file using the ssh-copy-id command:

ssh-copy-id -i ~/.ssh/id_ed25519.pub username@your_server_ip

3. Test the New Key:

Try connecting to your server using the ed25519 key to ensure it’s working correctly:

ssh -i ~/.ssh/id_ed25519 username@your_server_ip
If you can log in without any issues, your new key is set up correctly.

Conclusion

Upgrading to a modern ed25519 keypair resolves the “Exhausted available authentication methods” error associated with RSA keys. It’s a crucial step in improving your server’s security, as RSA keys with SHA-1 hash algorithms are no longer considered safe. Keep your private key secure, and consider adding a passphrase for an extra layer of protection.