Increase SSH Idle Timeout

To increase the SSH idle timeout, follow these steps:

  1. Open the SSH config file for editing using the command:
sudo nano /etc/ssh/sshd_config
  1. Add or modify the following values in the config file:
ClientAliveInterval 120
ClientAliveCountMax 30

Here's what these values do:

  • ClientAliveInterval sets the timeout interval in seconds. If no data is received from the client within this interval, sshd(8) will send a message to request a response. The default is 0, which means no messages are sent. This option applies to protocol version 2 only.

  • ClientAliveCountMax determines the number of client alive messages that can be sent without sshd(8) receiving any messages back from the client. If this threshold is reached, sshd will disconnect the client, terminating the session. It's important to note that client alive messages are different from TCPKeepAlive. The client alive messages are sent through the encrypted channel and cannot be spoofed. The default value is 3. This option applies to protocol version 2 only.

By setting ClientAliveInterval to 120 and ClientAliveCountMax to 30, the idle timeout will be approximately 1 hour (60 minutes). After making the changes, you need to restart the SSH service for the modifications to take effect. Run the following command:

sudo service ssh restart