How can I access a remote Linux VM behind a firewall?

Question

One of my customers runs a Linux VM on his PC and I need to access it remotely. This is a PC computer, not a server, so it is connected to the internet most of the time. It has a firewall too.

I need to administer this Linux VM sometimes to install new software or access its database. What is the best way for me to get remote access?

Note that this PC is on a normal at-home internet connection. Its IP address is not a server IP address, it's hidden behind the ISP provider. I am located at work in my office. If needed, I have a Linux PC server which has a fixed IP address at my disposal.

Answer 1

Maybe you can let the customer connect from within the VM to a system to which you can login (*1) and then use a reverse tunneling. E.g.:

ssh -R 2200:127.0.0.1:22 youripaddress

You then would connect on that system (*1) using

ssh -p 2200 localhost

"youripaddress" is the ip address/hostname of the "*1" system

Answer 2

Virtualbox has a great feature called VRDP, which mean that you can access this VM remotely (other virtualization apps prbably have similar features). I have been using it and it works great and is very fast. You can configure that on the VM's properties under the Display panel.

• Under Remote Display, you should tick the box for Enable Server

• Set the Authentication level (you can read about the different options at the link above) to the desired level.

• Additionally, I would highly recommend that you change the port number too, any random number above 1024 would do the trick.

You can use services like dyn-dns or no-ip to keep track of the dynamically changing IP adresses of his home router. Note that these services are free, and will update automatically.

Another point: If you are using a NAT router, you should forward a port to your computer (the one with the VM installed) in order to be able to connect to it through the router's firewall. The port number is the port that you set when you enable the VRDP option.

Additional info:

• A guide on how to setup & use Dyn-DNS.

Answer 3

The most important part is you that you select bridged adapter in the settings for the device. If you don't it might be creating a NAT which makes the machine hard to access without setting up another layer of port forwarding on your personal machine. This (setting up the bridged adapter) will create a network interface which can be accessed from your local network. Then you can set up your router to use port forwarding.

If setting this (bridged adapter) fails for compatibility reasons then you must set up internal port forwarding as well as through the router.

or use the NAT

Answer 4

One more alternative: Use TeamViewer for Linux.