How to Keep SSH Sessions Alive and Prevent Timeout

Overview

Many users want their SSH sessions to stay connected so that applications keep running or to avoid the frustration of re‑connecting after a period of inactivity. This guide shows how to prevent SSH session timeout until the terminal window is closed.

Why Does SSH Close?

The SSH daemon (sshd) on the remote server will terminate a connection if the client does not send any data for a configured period. To keep the connection alive, you can adjust settings on either the client or the server side.

Configuration Files

Both client and server have configuration files that can be edited to control keep‑alive behavior.

Client Configuration

The client file is $HOME/.ssh/config. If the file does not exist, create it:

mkdir $HOME/.ssh

touch $HOME/.ssh/config

chmod 600 $HOME/.ssh/config

Edit the file with your preferred editor (e.g., nano or vim) and add a host block:

Host example

Hostname example.com

ServerAliveInterval 240

This setting sends a keep‑alive packet every 240 seconds, but only for connections to example . To apply the rule to all hosts, use:

Host *

ServerAliveInterval 240

Optionally, limit the number of unanswered keep‑alive messages with ServerAliveCountMax:

Host *

ServerAliveInterval 240

ServerAliveCountMax 2

With this configuration the client will close the session after two consecutive unanswered intervals.

Server Configuration

The server file is /etc/ssh/sshd_config. Add the following lines (note the use of ClientAlive rather than ServerAlive):

ClientAliveInterval 60

ClientAliveCountMax 2

ClientAliveInterval

is specified in seconds; if the server receives no data from the client within this period, it sends a keep‑alive request. If the client fails to respond ClientAliveCountMax times, the server terminates the session.

Why Not Disable Timeouts Entirely?

Keeping an SSH session permanently open can be risky. On self‑hosted machines it may be acceptable, but on cloud platforms (e.g., AWS) idle sessions can incur charges because many providers bill per minute of server usage. Setting reasonable timeouts helps avoid unnecessary costs.

Conclusion

The article demonstrates how to create and edit SSH configuration files on both client and server, shows which parameters prevent session timeout ( ServerAliveInterval, ServerAliveCountMax, ClientAliveInterval, ClientAliveCountMax), and explains why it is generally better to use timeouts rather than keeping sessions alive indefinitely.