Secure Shell (SSH) is a protocol that provides secure command-line access to your server. However, when you’re idle for a while, the SSH connection can get disconnected due to various reasons, like network issues or server configurations. In this article, we’ll discuss how you can keep your SSH connection alive, even when you’re not actively using it.
To keep your SSH connection alive, you can modify the SSH client settings by adding the ServerAliveInterval and ServerAliveCountMax options to your SSH configuration. Alternatively, you can use the SSH command with these options directly when connecting to the server. If you are using PuTTY as your SSH client, you can enable the keepalive feature by setting the Seconds between keepalives option.
Understanding ServerAliveInterval and ServerAliveCountMax
To keep an SSH connection alive, you need to understand two important parameters: ServerAliveInterval and ServerAliveCountMax.
ServerAliveInterval: This parameter sets a timeout interval in seconds, after which if no data has been received from the server, SSH will send a message through the encrypted channel to request a response from the server.ServerAliveCountMax: This parameter sets the number of server alive messages which may be sent without receiving any messages back from the server. If this limit is reached while server alive messages are being sent, SSH will disconnect from the server, effectively terminating the session.
Modifying SSH Client Settings
You can modify the SSH client settings to keep the connection alive by adding the ServerAliveInterval and ServerAliveCountMax options to your SSH configuration.
Editing the .ssh/config File
Open the .ssh/config file in a text editor of your choice. If the file doesn’t exist, you can create it. Add the following lines:
Host examplehost
Hostname examplehost.com
ServerAliveInterval 180
ServerAliveCountMax 2In this configuration, ServerAliveInterval 180 means that the client will send a packet to the server every 180 seconds (3 minutes) if no data has been received in the meantime. ServerAliveCountMax 2 means that the client will try two times before closing the connection if no response is received.
Using SSH Command
Alternatively, you can add these options directly in the SSH command when connecting to the server:
ssh -o ServerAliveInterval=180 -o ServerAliveCountMax=2 $HOSTThis command will do the same thing as the configuration file method. It will send a packet to the server every 180 seconds and will try two times before closing the connection if no response is received.
Using PuTTY for SSH Connection
If you are using PuTTY as your SSH client, you can set the Seconds between keepalives option to a positive number to enable the keepalive feature. You can find this option under Connection in the PuTTY configuration.
Conclusion
Keeping an SSH connection alive is essential for long-running tasks and for maintaining a stable connection. By using the ServerAliveInterval and ServerAliveCountMax parameters, you can ensure that your SSH connection remains active even when you’re not using it.
Remember, the values for these parameters will depend on your specific use case and network conditions. So, it’s crucial to adjust them according to your needs. For more detailed information, you can refer to the SSH documentation.
Keeping your SSH connection alive can be a simple task with the right configuration. By following the steps in this guide, you can ensure a stable and continuous connection to your server.
Secure Shell (SSH) is a protocol that provides secure command-line access to a remote server. It allows you to securely connect to and manage your server remotely.
SSH connections can get disconnected when idle due to various reasons, such as network issues or server configurations. By default, SSH has a timeout period after which it will disconnect if no activity is detected.
You can keep your SSH connection alive by modifying the SSH client settings. This involves setting the ServerAliveInterval and ServerAliveCountMax parameters to send periodic messages to the server and prevent disconnections.
To modify the SSH client settings, you can edit the .ssh/config file or use the SSH command with the appropriate options. Both methods allow you to specify the ServerAliveInterval and ServerAliveCountMax values.
Yes, PuTTY is a popular SSH client for Windows. You can configure PuTTY to enable the keepalive feature by setting the "Seconds between keepalives" option in the PuTTY configuration.
The values for ServerAliveInterval and ServerAliveCountMax depend on your specific use case and network conditions. It’s recommended to start with a conservative interval, such as 180 seconds, and adjust the values based on your needs and the stability of your network connection.
You can refer to the SSH documentation for more detailed information about SSH configuration options and parameters. The documentation provides comprehensive explanations and examples to help you customize your SSH settings.
