ajr0
Contributor
Contributor

Dual monitor not working

I'm trying to figure out how to use 2 monitors. I'm running Ubunut 18.04 with a 4k monitor and an HD monitor. Both are recognized and work fine on the local machine.

The  horizon client is version 5.4.1 build 15988340.

i'm connecting to a windows 10 vm on a corporate network. In the guest Display settings, I only see a single display which is the 4k monitor so that is the first question, is true dual monitor at the guest OS level supported? At some point i could see both monitors in some horizon view, similar to what windows would show, ie 2 boxes that can be moved to be side by side or stacked. And they had checkable marks on them (checking both and applying did not show the 2nd monitor) But i no longer see any option in the horizon menu to show this view.

So i do not see any way to pick 2 monitors.

I have also tried stretching the guest desktop image across monitors in one of two ways.

1) If i position the desktop so that it overlaps both local monitors and select full screen - all monitors, then i get a very distorted image where it looks like it has dropped the resoution to HD. it is virtually unusable.

2) i tried was from windowed mode and with the desktop on the 4k monitor,  dragging  the vertical border onto the HD monitor. But for each pixel column the desktop is extended, it 'robs' a pixel on the other side, ie it turns black. So that there is never more than 3840 pixels on the virtual desktop.

Is this all consistent with what is supported in the linux horizon client or is there some way to run 2 monitors with independent resolutions?

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2 Replies
ajr0
Contributor
Contributor

I replaced my HD monitor with a 2nd 4K and upgraded to Linux Horizon client 2006. Everything else as in the OP.

It seems that the client still just does not want to go over 3840x2160.

In Full Screen - All monitors, the desktop only appears on one monitor.

In Windowed mode, if i stretch the desktop across both monitors, then it still will only display 3840 pixels. eg every pixel widens so that it is still only 3840 pixels wide on over both 4K monitors so everything looks stretched horizontally.

I also tried stacking the displays vertically in Ubuntu. When i tried to stretch the desktop vertically then the area over the 2nd monitor is just black.

FWIW the remote is  some sort of vmware desktop called 'HVD' with Windows 10 Enterprise.

Is this just not possible to have dual 4K monitors with the Linux client? Is the situation any better with the Windows client? Ie do local dual monitors appear as individual monitors in the virtual desktop or can the desktop at least stretch over them?

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dm27408
Enthusiast
Enthusiast

Per Best Practices for Using Multiple Monitors:

You can use up to four monitors if you have enough video RAM. To use more than two monitors to display your remote desktop on an Ubuntu client system, you must configure the kernel.shmmax setting correctly. Use the following formula: max horizontal resolution X max vertical resolution X max number of monitors X 4 For example, manually setting kernel.shmmax to 65536000 allows you to use four monitors with a screen resolution of 2560x1600.

You might need to increase your shared memory limit. On my system the limit is:

$ sysctl kernel.shmmax
kernel.shmmax = 18446744073692774399

Regards,

Dominik

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