I used the virtual machines in virtualbox in a "headless" mode instead of a GUI mode. what are the advantages of using it in a headless mode?? by headless does it mean that the server doesnt have a keyboard or monitor attached or does it mean that no window will "pop up" , denoting that it is ON(or any other status), when a virtual machine is worked with? what exactly does it mean? pls reply…
Mac – Virtualbox in Headless mode
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Related Solutions
I just solved this problem by clicking the green arrow "Show" at the top of the VirtualBox GUI while my headless instance was already running.
I could see what the VM window would look like inside the "Preview" Pane on the VirtualBox GUI, and after clicking "Show", the VM window came up as though I had initially powered on the machine from the Virtualbox GUI.
Edit: When you close the VM window, it will give you the additional option to "Continue running in the background", so your headless instance can revert to being headless again.
The window size is controlled by the VM's screen resolution. If you manually resize the window on the host you'll only zoom on the image returned by the VM, so of course this gives a very bad image quality.
Change the screen's resolution in the VM's configuration, either via the GUI, or directly via the command line with xrandr.
First run xrandr with no arguments, it'll display all outputs (in this case they're just the virtual outputs emulated by VirtualBox).
Screen 0: minimum 320 x 200, current 1024 x 768, maximum 8192 x 8192
VGA1 connected 1024x768+0+0 (normal left inverted right x axis y axis) 0mm x 0mm
...
Now run xrandr --output <output> --size <resolution> and replace "output" and "size" with the connected output that you got from the previous command (in this case VGA1) and the resolution you want to set, I recommend setting it just a bit lower than your actual monitor to leave space for the taskbar and Virtualbox window title bar.
Example : xrandr --output VGA1 --size 1920x1040.
Once you set the resolution in the VM, VirtualBox will automatically resize its window on the host.
By the way, here's the official Ubuntu documentation about changing the screen's resolution.
Best Answer
Headless mode just means that you won't see a window for it on your host. Use this if you are just intending to run a server and don't really care to see what is happening. You can always still RDP into it if you need to.