autossh: Keep SSH connections alive automatically

Keeping Your SSH Connections Alive Automatically with Autossh

In the world of server management, maintaining a stable and reliable SSH connection is crucial, especially when you're managing servers over unstable networks. This is where autossh comes into play. Autossh is a simple program that automatically restarts SSH sessions and tunnels in case of network disruptions or unexpected server reboots. In this blog post, we will delve into how you can use autossh to enhance your SSH experience, along with detailed installation instructions across various Linux distributions using apt, dnf, and zypper package managers.

What is Autossh?

Autossh is not a replacement for the SSH program itself; it acts as a wrapper to monitor and manage your SSH sessions. Utilizing autossh allows you to not worry about manually re-establishing your remote connections — making your work seamless and interruption-free.

Why Use Autossh?

Persistent Connection: Ideal for long-duration connections, particularly for remote working scenarios or when running lengthy scripts over SSH.
Automatic Reconnection: Automatically reconnects sessions after network downtime or server restart.
Minimal Configuration: Uses the same syntax and parameters as SSH, making it easy to integrate into your existing workflows.

Installation Instructions

For Ubuntu and Other Debian-based Distributions:

Update your package index:
```
sudo apt update
```
Install Autossh:
```
sudo apt install autossh
```

By entering these commands, your system will download and install the latest autossh package available in the repository.

For Fedora, CentOS, RHEL, and Similar:

Update your package manager (dnf):
```
sudo dnf makecache
```
Install Autossh using dnf:
```
sudo dnf install autossh
```

This will fetch and install autossh, ensuring you have the latest version supported by your distribution.

For openSUSE and SUSE Linux Enterprise:

Refresh Zypper's package list:
```
sudo zypper refresh
```
Install Autossh:
```
sudo zypper install autossh
```

Zypper will handle the dependencies and complete the installation process.

How to Use Autossh

Using autossh is very straightforward, as it incorporates all SSH command-line options. Here's a basic example to start an SSH connection that will be automatically restarted if it drops:

autossh -M 0 -o "ServerAliveInterval 30" -o "ServerAliveCountMax 3" -p [PORT] [USER]@[HOST]

Explanation of the flags:

-M 0: Tells autossh to dynamically choose a monitoring port for managing the connection or not use monitoring at all.
-o "ServerAliveInterval 30": This option sends a null packet to the server every 30 seconds to keep the connection alive.
-o "ServerAliveCountMax 3": If 3 consecutive alive messages are sent without any response, the connection is considered dead and restarted.
-p [PORT]: Specifies the SSH port.
[USER]@[HOST]: Your SSH credentials.

Conclusion

Autossh simplifies the management of SSH connections considerably by ensuring that you remain connected even when networks are unreliable. Its minimal configuration overhead and robust reconnection capabilities make it a valuable tool for developers, system administrators, and IT professionals.

Whether you're working remotely or running critical infrastructure tasks, integrating autossh into your setup can save time and prevent unnecessary disruptions. Give autossh a try and experience a more stable and persistent SSH environment.