Auto SSH service and keepalive

Posted under » Linux on 18 November 2024

openSSH is not enabled or installed by default on most OS. You have to install it on your own eg. this and this.

So you have to start the ssh daemon (sshd) automatically by using the systemctl enable command.

$ systemctl enable sshd

This doesn't start automatically so you can use the following commands too.

$ systemctl start sshd
$ systemctl status sshd

sshd which runs server-side, closes the connection from the server-side if the client goes silent. To prevent connection loss, instruct the ssh client to send a sign-of-life signal to the server once in a while.

The configuration for this is in the file $HOME/.ssh/config, create the file if it does not exist (the config file must not be world-readable, so run chmod 600 ~/.ssh/config after creating the file). To send the signal every e.g. four minutes (240 seconds) to the remote host, put the following in that configuration file:

Host lmao #if a particular host
    HostName aws.com
    ServerAliveInterval 240
    
Host * #all hosts
    ServerAliveInterval 240