[Solved] Linux guest display is less than the Windows host can offer (and secondary monitor enabled)

[taxedserf]

I'd be grateful for help on optimising the displays of a Linux guest on a Windows host.

The guest is Linux Mint Xfce 18.3 running on an HP Pavilion host running Windows 10x64.

The Linux guest has a maximum display size of 1024x768, but Windows 10 is currently using 1366x768. The Linux guest (using the GUI) reports only three display sizes: 1024x768, 800x600, 640x480. I want the Linux guest to run in 1366x768, and to detect a secondary monitor when one is attached to the host.

The Linux guest reports the VirtualBoxGuestAdditions is already installed.

The BIOS of the host is set to enable virtualisation.

Virtual Box has allocated to the Linux guest the attached display properties.

Virtual Box has greyed out the resolution options of the guest, as attached.

When a secondary monitor was attached to the Windows host, the Windows host used it normally, but the guest Linux couldn't see/detect the secondary monitor at all.

(And the shared clipboard between guest and host doesn't work; not part of this issue, but disclosed to give a clue as to what's happening.)

On a different laptop - a Lenovo Thinkpad - Virtual Box works exactly as expected. Flawlessly!

What is the first step to solving this? (Or proving a limitation?)

VirtualBox Version 5.2.16 r123759 (Qt5.6.2).

[arQon]

i haven't needed this in 5 years, but your problem sounded familiar, so maybe it'll help:

see http://forums.virtualbox.org/viewtopic.php?f=8&t=26050
> VBoxManage setextradata global GUI/MaxGuestResolution any

[taxedserf]

I tried the command

VBoxManage setextradata global GUI/MaxGuestResolution any

but it had no effect.

The Linux guest still reports only three resolutions (smaller than the maximum available) and only one monitor (of the two available).

[socratis]

We're going to need to see a VM log from a complete VM run:

• Start the VM from cold-boot (not from a paused or saved state) / Observe error / Shutdown the VM (force close it if you have to).
• With the VM completely shut down (not paused or saved), right-click on the VM in the VirtualBox Manager and select "Show Log".
• Save only the first "VBox.log", ZIP it and attach it to your response. See the "Upload attachment" tab below the reply form.

[taxedserf]

Sorry for the delay; other matters cropped up.

Since my last post, I have updated Virtual Box and half of the issue has solved itself. The Linux guest now correctly lists a wide range of display options.

The remaining issue is thus the number of monitors reported by guest Linux is lesser than available from host Windows.

I attach two ZIP files with the requested log file, plus three related screenshots.

[socratis]

The remaining issue is thus the number of monitors reported by guest Linux is lesser than available from host Windows.

The number of monitors is not automatically set from the host. You have to specifically set how many monitors you want in the VM Settings » Display » Monitor count.

[taxedserf]

When this is set to two monitors in the Windows host VirtualBox app, the Linux guest still cannot see the second monitor in its "Display" programme. Not screenshots yet to hand; will provide if requested (in due course).

[socratis]

In the screenshot you provided, your host seems to have only one monitor connected. That's why the whole slider is red. Are you actually having two monitors on your host?

[taxedserf]

The Windows host has two monitors and Windows is using both of them.

The VirtualBox monitor count is correctly set to 2 monitors, that is what I want VirtualBox to use.

The colour of the bar "monitor count" means nothing to me.

The Windows host is an HP with a secondary monitor plugged into its HDMI port.

It smells like the issue that, somehow, VB cannot see what Windows is actually using.

[socratis]

The Windows host has two monitors and Windows is using both of them.

In the first screenshot you attached to your post, your host had one monitor attached. In the second screenshot (that you included in the ZIP), your Windows host did indeed have two monitors attached.

Can you see the differences between the two images? There's a green area between 1 and 2 in the case where you actually use 2 monitors on your host, indicating that it's "OK" to use 2 monitors in your guest as well...

The colour of the bar "monitor count" means nothing to me.

"Means nothing to you"? Seriously now? For real? Don't be so "negative", I've heard that it causes flat-feet!

It smells like the issue that, somehow, VB cannot see what Windows is actually using.

Why does everyone and their cousin thinks immediately that it's VirtualBox's fault? I'll never get that...

The VirtualBox monitor count is correctly set to 2 monitors, that is what I want VirtualBox to use.

00:00:03.825404 MonitorCount <integer> = 0x0000000000000002 (2)

Correct. Your VirtualBox is setup with two monitors. However, I have the feeling that you haven't "Enabled" the second one. With the VM having the focus, go to the host's "View" menu » "Screen 1" and "Screen 2". Are they enabled? If not, enable them. What does the Display settings looks like in your guest? Does it see the two monitors?

Make sure that you have both screens enabled, as described above. Do not try to change the resolution from outside the guest, without the guest's actual knowledge. It's best if you change resolutions while the guest OS knows about it and controls it, instead of being enforced externally upon it.

There's one notable exception, and this is Full-Screen mode. Don't try to achieve your host's full screen resolution from within the guest, it will never happen (borders, frames, title bar, menu bar, status bar, etc...).

Finally, here's a reference from my log, that I didn't see in your VBox.log:

00:01:11.172760 GUI: UIMachineView::sltHandleNotifyChange: Screen=1, Size=1024x768
00:01:11.172773 GUI: UIFrameBufferPrivate::handleNotifyChange: Size=1024x768
00:01:11.179394 GUI: UIMachineView::sltHandleNotifyChange: Screen=0, Size=1280x1024
00:01:11.179407 GUI: UIFrameBufferPrivate::handleNotifyChange: Size=1280x1024

There's not a single reference to "Screen=1" on your log, further evidence that you don't have it enabled...


PS. For future reference, you should completely shut down the VM before grabbing the VBox.log, otherwise it's incomplete...

[taxedserf]

Many thanks for your review of the logs.

You have provided a solution!

There ended up being two issues in this ticket:

• failure by guest Linux to receive a complete list of available resolutions;
• failure by guest Linux to see a second monitor.

The first issue was solved by an update published by VB between July and September.

The second issue was solved by enabling the second monitor in VB while the guest was running (the virtual equivalent of plugging the monitor into the virtual machine).

For the second issue, the complete solution was:

• run VB.
• log into guest.
• in the host window containing the guest, as suggested above, View > Screen 2 > Enabled.
• nothing will have changed to the user. No tick box will appear next to "Enabled" and the list of resolutions available to the host (?) will remain greyed-out.
• go to the guest's display settings. In the case of Linux Mint, Start > "Display". There should now be - at last!!! - an image of two monitors, the second of which will be greyed out and marked (in actual readable words) "disabled".
• click to select the 2nd (disabled) monitor.
• click the box, "use this display".
• VB will immediately produce a second window containing the guest's second screen. The resolution of this second screen is set by the guest, not the host/VB.

I can't see the commercial use-case for presuming a secondary monitor be disabled by default when the resource allocation is set to multi-monitor. It's not a foreseeable choice. The VB installed on the other laptop - a Lenovo Thinkpad - didn't presume disablement of the secondary monitor, so why should this instance of VB on this laptop?

A side-issue arising is that users need to see colour. Apparently, colours on a sliding scale - pastel colours at that! - are not purely for decorative effect! Other elements on the same dialogue box produce real warnings with real words, so, presumably, no warnings means no issues. Yet, this standard is applied inconsistently on the same dialogue box screen. Moral of the story: believe nothing you see on-screen! And, apparently, don't be colour-blind.

[socratis]

Great, glad you got it going! And thank you for marking the topic as [Solved]...