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Repair common Windows errors and clear accumulated junk for a smoother, more stable PC - no reinstall needed.Free scan · no reinstallThis error usually means ssh-add cannot reach an SSH agent from the shell or process where you ran it. First check that process’s SSH_AUTH_SOCK; if you are using a Bourne-style Unix shell without a suitable agent, start one in that shell and add your key. The message alone does not mean a remote SSH server rejected your key.
What the error means
ssh-agent is a local helper that holds private keys for public-key authentication. SSH tools locate it through environment variables, including SSH_AUTH_SOCK, which identifies the agent’s socket. ssh-add must be able to reach that socket in its own environment; an agent process running somewhere on the machine is not sufficient if the failing shell cannot find or access it. See the OpenBSD ssh-agent manual and ssh-add manual.
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IBM documents the same wording as message FOTS0308 in its z/OS OpenSSH User’s Guide, Version 3.1.0, and identifies the need for a running agent and correctly exported agent environment variables.
Diagnose the failing shell
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In the exact terminal or process that produced the error, print the socket setting:
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printf '%sn' "$SSH_AUTH_SOCK"An empty value or a path to an obsolete socket is consistent with the process being unable to locate the agent.
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Ask the agent for its loaded identities:
ssh-add -lThe response distinguishes a connection problem from an empty agent, as described by the Stony Brook University Scientific Data and Computing Center’s SSH Agent guide.
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| Result | What it indicates | Next step |
|---|---|---|
| “Could not open a connection to your authentication agent.” | The command could not reach an agent from this process. | Check the socket and agent environment in this shell. |
| “The agent has no identities.” | The agent answered, but no keys are loaded. | Add the intended key with ssh-add. |
| A list of identities | The agent is reachable and has keys loaded. | If SSH still fails, investigate the SSH connection or key authorization separately. |
Start an agent and add a key in a Unix shell
For a Bourne-style shell such as sh or bash, evaluate the environment commands emitted by ssh-agent in the current shell, then add the key you want to use. Oracle’s OpenSSH client utilities guide documents this startup-and-add sequence.
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Start the agent and import its environment into the current shell:
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eval "$(ssh-agent -s)"The command output contains shell assignments that set the agent details, including the socket. Evaluating them here makes them available to commands subsequently run in this shell.
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Add the intended private key, substituting its actual path if different:
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ssh-add ~/.ssh/id_ed25519 -
Check that the agent can now answer:
ssh-add -l
Do not run the startup command automatically if your environment already starts or manages an agent. First check that SSH_AUTH_SOCK belongs to the agent intended for this session; starting another agent can leave you using a different one from the agent your other tools use.
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The eval pattern is for Bourne-style shells, not a universal command for every terminal or operating system. The agent prints commands for a shell to evaluate, so running that evaluation in a separate child process does not change the environment of an already-running parent shell. Run the setup in the shell that will run ssh-add, or use the matching setup method for your shell and agent provider. OpenSSH also documents running a child process under an agent as another setup approach in its ssh-agent manual.
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For z/OS, IBM specifically advises checking that SSH_AGENT_PID and SSH_AUTH_SOCK contain the agent data and are exported. For PowerShell, Windows services, WSL, containers, macOS-managed agents, or third-party key managers, the commands and integration depend on the installed OpenSSH build and provider. Check that provider’s documentation and verify which agent service or socket the failing process is configured to use rather than assuming the Unix command applies unchanged.
Keep the agent connection secure
An agent socket is a way for local processes to request authentication operations using keys held by the agent. The OpenBSD ssh-agent manual says the socket is accessible only to the current user, while warning that root or another process running as that same user can abuse it. Do not make the socket broadly accessible, and do not copy a private key to a remote server to fix a local agent-connection error.
Agent forwarding is a separate feature, not a fix for a local ssh-add connection failure. OpenSSH explains that forwarding does not send private keys or authentication passphrases over the network, but it does let remote processes request authentication operations through the forwarded agent connection while forwarding is active. Use it only when needed and with an understanding of that access.
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