ssh-agent-monitor

Keep your SSH agent socket working in long-running tmux sessions.

Problem

When using SSH agent forwarding with tmux:

1. You SSH into a machine with agent forwarding (creates /tmp/ssh-XXXX/agent.YYYY)
2. Start a tmux session
3. Disconnect and reconnect later (new socket created, old one gone)
4. tmux still has the old SSH_AUTH_SOCK, SSH operations fail

Solution

ssh-agent-monitor maintains a stable symlink at $XDG_RUNTIME_DIR/ssh-auth-sock that always points to the newest working SSH agent socket. Your shell and tmux sessions reference this symlink, which stays valid across reconnects.

Requirements

• Linux with systemd
• inotify-tools (for inotifywait)
• openssh-client (for ssh-add)

Installation

# Clone to recommended location
git clone git@github.com:msch/ssh-agent-monitor.git ~/.local/share/ssh-agent-monitor
cd ~/.local/share/ssh-agent-monitor

# Install (sets up systemd service, ~/.ssh/rc, and shell config)
make install

This will:

• Check that inotifywait and ssh-add are available
• Install and start the systemd user service
• Set up ~/.ssh/rc (creates a symlink to our script, or adds a line to run it if file exists)
• Detect your shell and add SSH_AUTH_SOCK export to .bashrc or .zshrc (.zshrc.local takes precedence if it exists)

Then restart your shell or run source ~/.bashrc (or ~/.zshrc, etc.).

How It Works

1. The monitor scans /tmp/ssh-* directories for agent sockets
2. Tests each socket with ssh-add -l to find a working one
3. Updates the symlink $XDG_RUNTIME_DIR/ssh-auth-sock atomically
4. Uses inotifywait to watch for socket changes
5. On new SSH connection, ~/.ssh/rc triggers a rescan by touching the symlink

Uninstall

make uninstall

This stops and disables the systemd service. If ~/.ssh/rc was a symlink to our script, it will be removed. If it was an existing file with a source line added, you'll be prompted to remove that line manually. The shell config modification is left in place for manual cleanup.

License

MIT