But when I tried to do the same for OpenSuse, I got into problem. I couldn't run the VBoxLinuxAdditions.run from the terminal. I received an error messaage saying that "Please install GNU make, Please install GNU compiler".
Then when I searched the web, I found this link quite useful.
As such, I executed this command in the OpenSuse terminal:
sudo zypper install gcc make automake autoconf kernel-source
It asked for my "root" password, and when i entered, it downloaded the necessary packages. (Though, i received an information that autoconf cannot be installed)
It took nearly 1 hour to download and install the necessary packages on my machine.
Then I ran the command:
sudo sh VBoxLinuxAdditions.run
after navigating to the appropriate "media" directory.
Then I was notified to restart the OS. And after that, I was able to use all the features I use with "ubuntu" as guest.
I also noticed that my OpenSuse resolution automatically increased to 1024x768 after installing the VirtualBox guest additions. (It was previously 800x600 only)