Second monitor not appearing in vbox

Discussions related to using VirtualBox on Windows hosts.
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applesauceowo
Posts: 5
Joined: 12. Oct 2021, 02:29

Second monitor not appearing in vbox

Post by applesauceowo »

The second montior isn't appearing despite being set to exist. The "enable" button on the dropdown for virtual screen 2 is NOT grayed out, implying the button can be pressed, but pressing it does nothing. any idea on how to fix? I just want to be able to use virtualbox with 2 virtual monitor screens



e; heres an image of the button, idk why but pressing it just doesn't do anything theres no error message and my guest OS doesn't detect anything other than the 1 monitor
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mpack
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Joined: 4. Sep 2008, 17:09
Primary OS: MS Windows 10
VBox Version: PUEL
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Re: Second monitor not appearing in vbox

Post by mpack »

It looks like you have not installed the Guest Additions. I don't know if that is necessary (I don't use multiple monitors in VMs), but it can't hurt.
Jetras
Posts: 20
Joined: 14. Sep 2021, 21:06
Primary OS: MS Windows 10
VBox Version: PUEL
Guest OSses: Windows (2012 & 10), Linux (RHEL, Ubuntu, CentOS), FreeBSD (pfSense)

Re: Second monitor not appearing in vbox

Post by Jetras »

I cannot install Guest Additions (keep getting an error during install), and I also was trying to do dual monitors, I believe after all my research that you NEED Guest Additions for this to work properly.
Shoot for the Moon, even if you miss you still made it among the stars!
applesauceowo
Posts: 5
Joined: 12. Oct 2021, 02:29

Re: Second monitor not appearing in vbox

Post by applesauceowo »

mpack wrote:It looks like you have not installed the Guest Additions. I don't know if that is necessary (I don't use multiple monitors in VMs), but it can't hurt.
I believe I have it installed, but the process of installation was not clear to me. So I may have made a mistake.

Anyway to check if its installed properly?
scottgus1
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Re: Second monitor not appearing in vbox

Post by scottgus1 »

Open the VM's vbox.log, search for the words "Guest Additions information report:". One of those lines will have the version of GAs installed if any.

Note that GAs in a Linux VM have prerequisites, same as for installing Virtualbox on a Linux host:
https://www.virtualbox.org/manual/ch02. ... nux-prereq
https://www.virtualbox.org/manual/ch04. ... ions-linux
applesauceowo
Posts: 5
Joined: 12. Oct 2021, 02:29

Re: Second monitor not appearing in vbox

Post by applesauceowo »

scottgus1 wrote:Open the VM's vbox.log, search for the words "Guest Additions information report:". One of those lines will have the version of GAs installed if any.

Note that GAs in a Linux VM have prerequisites, same as for installing Virtualbox on a Linux host:
https://www.virtualbox.org/manual/ch02. ... nux-prereq
https://www.virtualbox.org/manual/ch04. ... ions-linux
00:00:28.892853 VMMDev: Guest Additions information report: Version 6.1.26 r145957 '6.1.26'
00:00:28.892891 VMMDev: Guest Additions information report: Interface = 0x00010004 osType = 0x00053100 (Linux >= 2.6, 64-bit)

this was in the vbox.log. this should mean its installed correctly right?

I believe I have all prerequisites although I'm not super experienced with linux so i may have made a mistake

still it doesn't work


EDIT:

Something else I noticed, When I use fullscreen and click on view>Virtual Monitor 1 or 2> Use host screen 1 or 2

the screen will disappear and I have no way of getting it back even tho that the manager says the virtualmachine is still running, I dont know how to make it reappear so I'm always forced to shut it down or freeze it and then reopen it

the icon for the window will still be in the bottom but clicking on it does nothing and like i said at this point I can only stop and restart the system using the manager
scottgus1
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Re: Second monitor not appearing in vbox

Post by scottgus1 »

The line shows a good GA install.

Please Start the VM from full normal shutdown, not save-state. Run until you see the problem happen, then shut down the VM from within the VM's OS if possible. If not possible, close the Virtualbox window for the VM with the Power Off option set.

Right-click the VM in the main Virtualbox window's VM list, choose Show Log. Save the far left tab's log and the hardening log next to it, zip them, and post the zip file, using the forum's Upload Attachment tab.
applesauceowo
Posts: 5
Joined: 12. Oct 2021, 02:29

Re: Second monitor not appearing in vbox

Post by applesauceowo »

scottgus1 wrote:The line shows a good GA install.

Please Start the VM from full normal shutdown, not save-state. Run until you see the problem happen, then shut down the VM from within the VM's OS if possible. If not possible, close the Virtualbox window for the VM with the Power Off option set.

Right-click the VM in the main Virtualbox window's VM list, choose Show Log. Save the far left tab's log and the hardening log next to it, zip them, and post the zip file, using the forum's Upload Attachment tab.
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mpack
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Re: Second monitor not appearing in vbox

Post by mpack »

This is not good.
00:00:03.037191 Host RAM: 8108MB (7.9GB) total, 4472MB (4.3GB) available
...
00:00:03.240252 RamSize <integer> = 0x0000000100000000 (4 294 967 296, 4 096 MB, 4.0 GB)
That's cutting it too fine on available RAM. Also, while you do have the GAs installed you have not enabled hardware acceleration.

I would reduce VM RAM to 3072MB, enable 3D acceleration, and increase graphics RAM to 256MB. Then let's see where that takes us.
Jetras
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Primary OS: MS Windows 10
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Guest OSses: Windows (2012 & 10), Linux (RHEL, Ubuntu, CentOS), FreeBSD (pfSense)

Re: Second monitor not appearing in vbox

Post by Jetras »

mpack wrote: ...and increase graphics RAM to 256MB.
How can you increase the Graphics RAM? My max is 128MB.

Nvermind, I found it:

Code: Select all

VBoxManage modifyvm "Name of VM" --vram 256
Last edited by Jetras on 15. Oct 2021, 17:24, edited 1 time in total.
Shoot for the Moon, even if you miss you still made it among the stars!
mpack
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Re: Second monitor not appearing in vbox

Post by mpack »

Jetras wrote: How can you increase the Graphics RAM? My max is 128MB.
I discovered just today that VirtualBox currently limits Linux guests to 128MB for some reason. Better stick with that. Do enable 3D acceleration however.
Jetras
Posts: 20
Joined: 14. Sep 2021, 21:06
Primary OS: MS Windows 10
VBox Version: PUEL
Guest OSses: Windows (2012 & 10), Linux (RHEL, Ubuntu, CentOS), FreeBSD (pfSense)

Re: Second monitor not appearing in vbox

Post by Jetras »

mpack wrote: I discovered just today that VirtualBox currently limits Linux guests to 128MB for some reason. Better stick with that. Do enable 3D acceleration however.
I found that you can get around the limitation with:

Code: Select all

VBoxManage modifyvm "Name of VM" --vram 256
and I haven't had any issues yet.
Shoot for the Moon, even if you miss you still made it among the stars!
mpack
Site Moderator
Posts: 39156
Joined: 4. Sep 2008, 17:09
Primary OS: MS Windows 10
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Guest OSses: Mostly XP

Re: Second monitor not appearing in vbox

Post by mpack »

The question was never "would it cause problems", it was "would it just waste RAM". And the answer appears to be: yes.
Jetras wrote:

Code: Select all

VBoxManage modifyvm "Name of VM" --vram 256
We got feedback from the devs on the VRAM limitation with Linux guests. It's not an error or an oversight. Linux uses a different mechanism than Windows to get accelerated graphics, so the extra simulated graphics RAM simply isn't needed. All you need is enough for basic buffering of (say) two or three frames. A 4K frame is around 33MB, so 128MB gives you 4 frames. Even two 4K monitors should be ok, though that does admittedly take you a lot closer to the margin.
applesauceowo
Posts: 5
Joined: 12. Oct 2021, 02:29

Re: Second monitor not appearing in vbox

Post by applesauceowo »

mpack wrote:
Jetras wrote: How can you increase the Graphics RAM? My max is 128MB.
I discovered just today that VirtualBox currently limits Linux guests to 128MB for some reason. Better stick with that. Do enable 3D acceleration however.
3D acceleration causes my guest OS to mostly break, this might be a problem with the guest OS rather than vbox however but i'm not sure

edit: i'll try some more stuff and come back afterward
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