autossh:tldr:4ddc4

The given command is using the autossh command-line tool to establish a stable and persistent SSH tunnel.

Here is a breakdown of each option used in the command:

• autossh: It starts the autossh utility for automatically establishing and maintaining SSH connections.
• -f: It stands for "fork" and causes autossh to run in the background as a daemon.
• -M 0: It specifies the monitoring port used by autossh. In this case, it is set to 0, which means that autossh will dynamically allocate a monitoring port.
• -N: It tells autossh not to run any remote command after establishing the SSH connection. This is often used when setting up port forwarding or tunneling only.
• -o "ServerAliveInterval 10": It sets the SSH server alive interval to 10 seconds. This means that autossh will send a keep-alive message to the SSH server every 10 seconds to ensure the connection remains active.
• -o "ServerAliveCountMax 3": It sets the maximum number of consecutive server alive messages that can be sent without getting a response before autossh terminates the connection. In this case, it is set to 3, meaning the connection will be terminated if no response is received after 3 consecutive keep-alive messages.
• "${ssh_command}": It is a placeholder for the specific SSH command or destination you want to connect to. It should be replaced with the actual SSH command or hostname.

Overall, this command configures autossh to establish an SSH connection and maintain it by sending regular keep-alive messages to the server. It allows for automatic reconnection in case the connection is dropped or lost.