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>> No. 24553 Anonymous
19th August 2015
Wednesday 5:36 pm
24553 Virtualised OS screen resolution
I run a number of virtual machines on my laptop in VirtualBox. The host OS is Windows 7, the guests are various Linux distributions.

Now why some distros [1] are able to run in full screen resolution (that is, 1366×768) while the others [2] tend to stick to 1024×768? What governs the max. available resolution for the VM?

My first guess was to fiddle with VirtualBox Guest Additions. I tried installing these into Fedora 20 VM. No result.

[1] openSUSE, Debian occasionally although not sure.
[2] Fedora, Arch, Debian, perhaps Ubuntu.
Expand all images.
>> No. 24560 Anonymous
19th August 2015
Wednesday 7:08 pm
24560 spacer
Xubuntu runs at the correct resolution for me in VB 5.0.1, although I recall it didn't at first before magically fixing itself after a few boots.
>> No. 24589 Anonymous
20th August 2015
Thursday 4:34 pm
24589 spacer
I haven't ben extreme distro hopping for a few years, but I remember it wasn't uncommon a while back to get fucked resolutions on some distros and not others. Could be the problem would show whether the machine is virtual or not. Can't really say without trying them both though.
>> No. 24594 Anonymous
20th August 2015
Thursday 7:08 pm
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> What governs the max. available resolution for the VM?

I'm not overly familiar with vbox internals, at least when compared to vmware, but my own educated stab in the dark would be differences in the guest-level X11 version and/or graphics drivers.

Modern hypervisors essentially allow guests to (appear to) "talk" directly to the host GPU / video card / driver, while my understanding is that vbox doesn't support this technology and doesn't plan to in the near future. Instead it still uses "virtual graphics cards" which emulate, to the best of their ability, the guest's configured video setup in software before passing it back to the host for rendering.

If guests are indeed responsible for their own graphics compositing, and given that different Linux distributions and versions thereof can come with wildly different kernel (and therefore driver) versions as well as opensource or proprietary videocard drivers etc, it would follow that different versions and distributions would have varying degrees of graphics performance when virtualized in this way.

You can probably fix just about anything by dicking around with your guests' Xorg configurations (http://linux.die.net/man/5/xorg.conf), however you might find that the cure (or at least the path to it) is worse than the disease.
>> No. 24602 Anonymous
21st August 2015
Friday 3:46 pm
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LiveCDs, be it Fedora or openSUSE or Ubuntu, tend to behave normally on that machine. I've never had any problems with the display.
> Instead it still uses "virtual graphics cards"
Aye, VirtualBox uses Innotek something-something video adapter if I recall it correctly.
> wildly different kernel
That's an idea. I'll try diff-ing kernel configurations on those VMs. Maybe fiddle with xrandr too. Cheers.
>> No. 24603 Anonymous
22nd August 2015
Saturday 1:49 pm
24603 spacer
>virtual graphics cards

Is this why by default VB only assigns something tiny like 12MB of VRAM?

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