SSH connection alive and prevent it from timing out (heartbeat)

To keep an SSH connection alive and prevent it from timing out, you can use the ServerAliveInterval option in your SSH client configuration or command line. This option sets the interval at which the client sends keepalive messages to the server. Additionally, the ServerAliveCountMax option controls how many unanswered keepalive messages trigger a connection termination. 

To set the heartbeat interval in your SSH client configuration:

1. Locate the SSH configuration file: The file is typically located at ~/.ssh/config for user-specific settings, or /etc/ssh/ssh_config for system-wide settings.
2. Add or modify the following lines: 

Code

Host *
  ServerAliveInterval 60
  ServerAliveCountMax 3

• Host * applies the settings to all hosts. You can specify a particular host instead, like Host example.com. 
• ServerAliveInterval 60 sets the interval to 60 seconds. 
• ServerAliveCountMax 3 closes the connection if 3 consecutive keepalive messages are not acknowledged. 

To set the heartbeat interval directly in the SSH command: 

Code

ssh -o ServerAliveInterval=60 -o ServerAliveCountMax=3 user@hostname

Explanation:

• ServerAliveInterval: Specifies the interval (in seconds) at which the client sends keepalive messages (also known as “hellos”) to the server. If the server doesn’t respond within this interval, the client will send another keepalive. If the server fails to respond after ServerAliveCountMax intervals, the connection is dropped.
• ServerAliveCountMax: Defines the number of unanswered keepalive messages that will trigger a disconnection.