How to keep SSH connections "alive"

If you're a regular SSH user, you've probably noticed that it sometimes "disconnects itself." To correct this, you just have to get your hands "a bit dirty" and change some configuration files.

To do this, you have to change the values ​​assigned to 2 variables ServerAliveCountMax and ServerAliveInterval.

ServerAliveCountMax sets the number of "server is alive" messages that can be sent without ssh receiving a response from the server. This type of message is essential to know if the connection is still active or not (perhaps the server "went down", etc.).

ServerAliveInterval sets the interval (in seconds) after which, in case of no response from the server, ssh will resend a message requesting a response.

On the client

For the changes to have effects for all users, the file must be modified  / Etc / ssh / ssh_config. On the other hand, if you want the changes to only take effect for your user, modify the file ~ / .ssh / config.

Add the following in the SSH configuration file:

Host*
    ServerAlive Interval 300
    ServerAliveCountMax 3

On the server

In order for the server to keep the connections with all clients alive, add the following in the file / Etc / ssh / sshd_config:

ServerAlive Interval 300
ServerAliveCountMax 3

This configuration causes the client / server to send a message to the counterpart every 300 seconds (5 minutes) and to give up at the 3rd opportunity if it has not received any response.