In this article I’ll show you how to set up a Linux running in VirtualBox to be able to access a service running on localhost on the host machine. I’ll use MySQL as an example, because that was the problem I faced with. The Linux OS of my choice is Ubuntu.
Testing the connection
First, let’s see how you can test if your virtual machine can access the service on the host. There is a great program called nmap for it. If it is not installed, you can install it with the following commands:
sudo apt-get update sudo apt-get install nmap
Let’s suppose we have a web application that is trying to connect to the MySQL server on localhost:3306 by default. We would not like to change this configuration, but allow our virtual linux to connect to the MySQL server running on the host.
So, first let’s check if we can connect to MySQL:
nmap -p 3306 localhost
You could see something like this, indicating that it cannot connect:
Starting Nmap 7.01 ( https://nmap.org ) at 2016-09-18 19:12 CEST Nmap scan report for localhost (127.0.0.1) Host is up (0.000053s latency). PORT STATE SERVICE 3306/tcp closed mysql
You should see an “open” STATE in the output instead of “closed”. Let’s try to resolve that.
Map localhost in the hosts file
We would like for our virtual linux to map localhost calls to the host machine. For this, we have to determine the default gateway of our machine.
Destination Gateway Genmask Flags MSS Window irtt Iface 0.0.0.0 10.0.2.2 0.0.0.0 UG 0 0 0 enp0s3 10.0.2.0 0.0.0.0 255.255.255.0 U 0 0 0 enp0s3 169.254.0.0 0.0.0.0 255.255.0.0 U 0 0 0 enp0s3 root@relevart-VirtualBox:/media/sf_Projects/Java/#
Check the Gateway in the 0.0.0.0 line. That 10.0.2.2 IP address is what we need.
Open /etc/hosts and comment out the default line for localhost mapping and add a new one like this:
#127.0.0.1 localhost 10.0.2.2 localhost
After saving the file, and running nmap again, you should see that the STATE of the port is “open”.