How to fix The agent has no identities. in SSH

First, check if ssh-agent is currently running. If it is not running, start it:

eval "$(ssh-agent -s)"

This command starts ssh-agent and sets the necessary environment variables (SSH_AUTH_SOCK and SSH_AGENT_PID). The eval statement is important because it executes the output in your current shell.

Use ssh-add to load your private key into the agent. The default key location is ~/.ssh/id_rsa:

ssh-add ~/.ssh/id_rsa

If you are using a different key name (ed25519, id_dsa, etc.), specify that path:

ssh-add ~/.ssh/id_ed25519

You will be prompted to enter your key's passphrase if it has one. Once entered, the key is loaded into the agent.

Confirm that your key is now loaded in the agent:

ssh-add -l

This lists the fingerprints of all identities currently held by the agent. You should see your key listed with its fingerprint and key type (RSA, ED25519, etc.).

Alternatively, use -L to see full public key details:

ssh-add -L

SSH is strict about file permissions for security. Incorrect permissions can prevent the agent from using your key. Set the correct permissions:

chmod 700 ~/.ssh
chmod 600 ~/.ssh/id_rsa
chmod 644 ~/.ssh/id_rsa.pub

The private key (id_rsa) must be readable only by you (600). The public key can be world-readable (644). The ~/.ssh directory must be accessible only by you (700).

By default, keys added to ssh-agent are lost when you close your terminal. To automatically load keys when you connect via SSH, add this to your ~/.ssh/config file:

Host *
    AddKeysToAgent yes
    IdentityFile ~/.ssh/id_rsa

Replace id_rsa with your actual key name if different. On macOS, you can also use the UseKeychain option to store passphrases in the system keychain:

Host *
    AddKeysToAgent yes
    UseKeychain yes
    IdentityFile ~/.ssh/id_rsa

Once your key is loaded, test that authentication works:

ssh -v user@hostname

The -v flag shows verbose output. Look for a line indicating "Offering public key" followed by "Authentication succeeded" or a similar message. If authentication still fails, check that your public key is added to ~/.ssh/authorized_keys on the remote server.