Can't start X11 in Hyper-V VM because "no screen detected"

[sgraf812]

Here's a screenshot of my X.log: https://usercontent.irccloud-cdn.com/file/P368XbTL/X.log.png

I added a RemoteFX Graphics Card to my Hyper-V machine config, to no avail. I played around with the hypervGuest module, but it had no effect.

When I asked around on #nixos, someone suggested a fix for this: I had to add services.xserver = { modules = [ pkgs.xorg.xf86videofbdev ]; videoDrivers = [ "hyperv_fb" ]; }; and now all is well. The question is: Couldn't hypervGuest do this automatically for me?

[steeleprice]

This does indeed work as a workaround to the problem still in 19.09. Is this a result of detection from nixos/modules/virtualisation/hyperv-guest.nix ?

I believe that would be the right location for the change as Home Manager doesn't seem to be the right place to put this, it should be the result of detection.

[stale]

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[tportNAPA]

Just ran into this.

[abctaylor]

This REALLY helped me!

[hisakiyo]

Thx dude, saved me

[SandwichChef]

Even using:
services.xserver = { modules = [ pkgs.xorg.xf86videofbdev ]; videoDrivers = [ "hyperv_fb" ]; };
It still doesn't work for me, are there any additional workarounds that any of you have had to use?

[hisakiyo]

Even using:
services.xserver = { modules = [ pkgs.xorg.xf86videofbdev ]; videoDrivers = [ "hyperv_fb" ]; };
It still doesn't work for me, are there any additional workarounds that any of you have had to use?

Can you share your X.log?

[SandwichChef]

Remarkably, I can't even find one. find / -name "X.log" returns nothing, and /var/log is empty except for journals.

Anyways, it appears that it has something to do video memory.

https://files.catbox.moe/mtsn2n.jpg

[stale]

I marked this as stale due to inactivity. → More info

[alex-ashery]

Wanted to report I have the same issue as @SandwichChef, tried running NixOS 22.05 on a Gen 1 and Gen 2 Hyper-V guest on Windows 10. Disappointed that I can't easily test NixOS in a VM without running into graphics issues.

[Diti]

Not stale.

[Ruzihm]

Not stale

[ElDavoo]

I got /dev/fb0: Permission denied. As written here , I had to:
users.users.gdm { extraGroups = [ "video" ] } .
And also add my user to video group.

[pingarelho]

Still an issue. Can't get either X nor Wayland running on Nix OS using Hyper-V.

[on3iropolos]

The following works for me.

1. Install as usual with gnome and gdm.
2. Before restarting, add the following lines to your configuration.nix found at a path like /tmp/.../etc/nixos/configuration.nix

services.xserver = { modules = [ pkgs.xorg.xf86videofbdev ]; videoDrivers = [ "hyperv_fb" ]; };
users.users.gdm { extraGroups = [ "video" ]; };
users.users.XXYOURUSERNAMEXX { extraGroups = [ "video" ]; };

3. Reboot
4. If it still doesn't work, after a failed login (reaching blank underscore due to X failing) you can press ALT-F2 to init a new session to login with root.
5. Don't forget to run sudo nixos-rebuild switch after changes.

I also changed services.printing.enable to false although I don't think this was part of the solution.

[JojOatXGME]

I recently started to look into Hyper-V as well, as I had some problems with VirtualBox on Windows (subpar performance, random freezes). The steps suggested by @on3iropolos fixed the problem for me as well. However, hyperv_fb had a low frame rate for me. This causes some a rather unpleasant UI experience. I found the following solution as an alternative:

# The video driver hyperv_fb seems to cause a low frame rate.
boot.blacklistedKernelModules = [ "hyperv_fb" ];

See also https://askubuntu.com/a/1336377. Linux 5.14 introduced hyperv_drm, which I think is used by default after you block hyperv_fb. I am not that familiar with the technical details, but it seems that fb (framebuffer) and drm (Direct Rendering Manager) are two different kinds of video drivers implementing a different interface. Anyway, with this new driver, you no-longer need the options suggested by @on3iropolos.

Maybe it is possible to update virtualisation.hypervGuest.enabled = true;, so that it uses hyperv_drm by default? (The option is enabled by the installer automatically.) It currently explicitly enables hyperv_fb.

Besides that, I also had to take the following three steps to make everything work on Hyper-V (Generation 2):

1. Use the GNOME ISO (if you want a graphical installer) as the Plasma Desktop ISO does not boot properly on Hyper-V
2. Disable Secure Boot (Hyper-V Quick Create does it for you)
3. Enable kernel option vm.overcommit_memory as suggested by Out of memory on package installation nix#421 (comment)

   # Sometimes applications may "randomly" run out of memory on Hyper-V.
   # This is probably caused by some non-optimal interaction between the
   # Linux kernal and the dynamic memory allocation of Hyper-V. The
   # following option fixes the issue.
   boot.kernel.sysctl."vm.overcommit_memory" = "1";

The guest integration of Hyper-V is unfortunately far behind VirtualBox and VMware. I have not yet found a solution to enable the enhanced session mode. I hope I will find a solution for that as well.

PS: If you made an error during the installation and cannot boot the system, you can change the configuration of an installed system after booting the installer from an ISO.

lsblk # To identify the right partions.
# I will assume sda2 being the root partition, and sda1 being the boot partition.
sudo mount /dev/sda2 /mnt
sudo mount /dev/sda1 /mnt/boot
sudo vim /mnt/etc/nixos/configuration.nix # Adjust your configuration
sudo nixos-enter -- nixos-rebuild boot