How to fix Error connecting to agent: No such file or directory in SSH

First, verify whether an SSH agent process exists:

ps aux | grep ssh-agent

You should see a line like:

user  12345  0.0  0.1  8192  1024 ?  Ss  10:30  0:00  ssh-agent

If no ssh-agent process appears, the agent is not running. Proceed to step 2 to start it.

If the agent is running, check the SSH_AUTH_SOCK variable:

echo $SSH_AUTH_SOCK

It should output something like /tmp/ssh-XXXXXXXXXX/agent.12345 or /run/user/1000/ssh-agent.socket. If it's empty or unset, proceed to step 2.

The most reliable way to start SSH agent in a new terminal session is:

eval "$(ssh-agent -s)"

This command:
1. Starts a new SSH agent process
2. Outputs shell commands to set environment variables (SSH_AUTH_SOCK, SSH_AGENT_PID)
3. eval executes those commands in your current shell

After running this, verify it worked:

echo $SSH_AUTH_SOCK
ssh-add -l

The second command should return either your loaded keys or "The agent has no identities" (which is fine—it just means no keys are loaded yet).

On macOS and BSD, the same command works:

eval "$(ssh-agent -s)"

Note: ssh-agent does not have a -K flag. (-k lowercase *kills* a running agent, and -K is an ssh-add option on macOS, not an ssh-agent option.) On macOS you usually don't even need to start the agent manually—launchd starts one automatically and sets SSH_AUTH_SOCK to a path under /private/tmp/com.apple.launchd.*/Listeners. To store a key passphrase in the macOS Keychain when adding the key, use the ssh-add flag instead (see step 3):

ssh-add --apple-use-keychain ~/.ssh/id_ed25519   # older macOS: ssh-add -K

Once the agent is running, load your SSH private key:

ssh-add ~/.ssh/id_ed25519

If your key has a different name or location:

ssh-add ~/.ssh/id_rsa
ssh-add ~/.ssh/github-key

You'll be prompted for the key's passphrase (if it has one). After entering it, the key is now loaded in the agent.

On macOS, add --apple-use-keychain to store the passphrase in the Keychain so you aren't prompted on future logins:

ssh-add --apple-use-keychain ~/.ssh/id_ed25519

Verify the key is loaded:

ssh-add -l

Should show output like:

256 SHA256:abcdef... user@host (ED25519)

To avoid running eval ssh-agent in every new terminal, add it to your shell startup file.

For bash, add to ~/.bashrc:

if [ -z "$SSH_AUTH_SOCK" ]; then
  eval "$(ssh-agent -s)"
  ssh-add ~/.ssh/id_ed25519 2>/dev/null
fi

For zsh, add to ~/.zshrc:

if [ -z "$SSH_AUTH_SOCK" ]; then
  eval "$(ssh-agent -s)"
  ssh-add ~/.ssh/id_ed25519 2>/dev/null
fi

For fish, add to ~/.config/fish/config.fish:

if not set -q SSH_AUTH_SOCK
  eval (ssh-agent -c)
  ssh-add ~/.ssh/id_ed25519 2>/dev/null
end

The condition [ -z "$SSH_AUTH_SOCK" ] ensures the agent is only started once per session. After adding this, reload your shell:

source ~/.bashrc

On macOS, prefer letting launchd manage the agent and use ssh-add --apple-use-keychain plus an ~/.ssh/config entry (AddKeysToAgent yes, UseKeychain yes) instead of starting ssh-agent in your shell rc file.

On some Linux desktops, GNOME Keyring stopped providing the SSH agent by default, so SSH_AUTH_SOCK is never set.

Step 1: Enable the gcr-ssh-agent socket:

systemctl --user enable gcr-ssh-agent.socket
systemctl --user start gcr-ssh-agent.socket

Step 2: Set SSH_AUTH_SOCK environment variable persistently:

mkdir -p ~/.config/environment.d
echo "SSH_AUTH_SOCK=$XDG_RUNTIME_DIR/gcr/ssh" > ~/.config/environment.d/ssh_auth.conf

Step 3: Log out and back in (or restart your desktop session) for changes to take effect.

Verify it's working:

echo $SSH_AUTH_SOCK
ssh-add -l

Sometimes SSH_AUTH_SOCK points to a different path than the actual agent socket.

Check what the agent is actually using:

ps aux | grep ssh-agent | grep -v grep

And check what SSH_AUTH_SOCK is set to:

echo $SSH_AUTH_SOCK

If they don't match, try killing the agent and restarting it:

pkill ssh-agent
eval "$(ssh-agent -s)"

For systemd user service setup, if you're using a service unit, ensure your SSH_AUTH_SOCK is correctly set. For example, add to your service unit file:

[Service]
Environment="SSH_AUTH_SOCK=%t/ssh"

Or set it in environment.d files:

echo "SSH_AUTH_SOCK=$XDG_RUNTIME_DIR/ssh" > ~/.config/environment.d/sshauth.conf

On Windows, SSH agent setup is different.

Step 1: Start the SSH Agent service:

# Run PowerShell as Administrator
Set-Service ssh-agent -StartupType Automatic
Start-Service ssh-agent
Get-Service ssh-agent

Step 2: Add your key using ssh-add:

ssh-add C:\Users\YourUsername\.ssh\id_ed25519

Step 3: Verify it works:

ssh-add -l

If ssh-add still fails, ensure you're using Windows' native OpenSSH (not Git Bash's bundled version). Use the full path:

C:\Windows\System32\OpenSSH\ssh-add.exe -l

If that works but regular ssh-add doesn't, add the Windows OpenSSH directory to your PATH environment variable.