How To SSH into a Machine and Launch an Interactive Command Line Program

In this article, we’ll discuss how to SSH into a machine and launch an interactive command line program. This is a common task for system administrators and developers working with remote servers. We’ll cover the process step-by-step, explaining each command and its parameters for better understanding.

What is SSH?

SSH, or Secure Shell, is a protocol used to securely log into remote systems. It is the most common way to access remote Linux and Unix-like servers. SSH provides strong password authentication and public key authentication, as well as encrypted data communications between two computers connected over the internet.

SSH Basics

To SSH into a machine, you typically use the ssh command followed by the username and the host IP address, like so:

ssh user@host

In this command, user is the username and host is the hostname or IP address of the remote machine.

Launching an Interactive Command Line Program

Sometimes, you may want to run an interactive command line program on the remote machine. To do this, you can use the -t option with the ssh command to allocate a pseudo-terminal. This allows you to interact with the remote command line program.

Here’s an example:

ssh -t user@host 'command'

In this command, command is the command you want to run on the remote machine.

Example: Launching yRouter

Let’s say you want to launch the interactive command line program yRouter on the remote machine. You can do this by replacing command with the command to launch yRouter:

ssh -t -i key.pem -o StrictHostKeyChecking=no ubuntu@ip_address 'yRouter/src/yrouter --interactive=1 user'

Here’s what each parameter does:

• -t: This option forces pseudo-terminal allocation. This can be useful for running interactive programs on the remote machine.
• -i key.pem: This option specifies the path to your private key file. Replace key.pem with the path to your private key file.
• -o StrictHostKeyChecking=no: This option disables strict host key checking. This can be useful when connecting to a new remote machine for the first time.
• ubuntu@ip_address: Replace ubuntu with your username and ip_address with the IP address of the remote machine.
• 'yRouter/src/yrouter --interactive=1 user': This is the command to launch yRouter with its arguments.

Keeping the Terminal Open

If you want to keep the terminal open after running the command, you can use the xterm -e command to execute the ssh command within the terminal window. Here’s an example:

xterm -e ssh -t -i key.pem -o StrictHostKeyChecking=no ubuntu@ip_address 'yRouter/src/yrouter --interactive=1 user'

This will open an xterm window, SSH into the remote machine, and launch the yRouter program. The terminal window will remain open with the yRouter program running.

Using Python to Execute the Command

If you’re working with Python, you can use the subprocess module to execute the command. Here’s an example:

import subprocess

subprocess.call(['xterm', '-e', 'ssh', '-t', '-i', 'key.pem', '-o', 'StrictHostKeyChecking=no', 'ubuntu@ip_address', 'yRouter/src/yrouter', '--interactive=1', 'user'])

This will achieve the same result as the previous example, but using Python.

Conclusion

In this article, we’ve covered how to SSH into a machine and launch an interactive command line program. We’ve discussed the ssh command and its parameters, and we’ve provided examples for launching an interactive program and keeping the terminal open. We hope you find this guide helpful as you work with remote servers.

import subprocess

subprocess.call(['ssh', '-t', 'user@host', 'command'])