Document disabling seamless mode

[RandyTheOtter]

Fixes QubesOS/qubes-issues#1945

• Basic intro
• Basic debian instructions
• Basic fedora instructions
• How to revert
  • Debian
  • Fedora
• Limitations, e.g. qvm-copy won't work
• Make screenshots for the intro
• Add a link to similar documentation for windows

---

Problems:

• Why fedora requires setting kernel?
  It doesn't, but it requires some features and kernelopt shenanigans
• Why fedora won't take kernelopt like debian?
  It only works with qubes kernel
• Why lightdm autologin doesn't work on fedora?
  It works, I must've made a typo in the config file or something
  No I haven't! It seems like on fedora user must log in at least once for autologin to start working.

[RandyTheOtter]

Not sure if I should make GUI instructions with screenshots as well or not. In this case specifically I don't like this idea because it will involve screenshots of the settings menu with just a couple of changes (that should be highlighted somehow to even find them in a settings menu screenshot), I think it will make instructions unnecessarily long. Besides, advanced users should already know things like that or be fine with CLI.

Perhaps add :menuselection:s? Also I don't think there is a way to set kernelopts in GUI.

[RandyTheOtter]

For whatever reason fedora template doesn't have fbdev_drv.so and vesa_drv.so in /usr/lib64/xorg/modules/drivers and I don't know why. Debian has them and uses them with qubes kernel.

When fedora is running with distribution kernel, however, Xorg uses /dev/dri/card0 after failing to load fbdev_drv.so and vesa_drv.so with libglamoregl.so and it works.

When running with qubes kernel, neither fedora or debian have /dev/dri/card0.

Fedora doesn't have a package that could provide fbdev_drv.so.

[RandyTheOtter]

I think that should be it from the technical standpoint, now I need somebody with a fresh pair of eyes to highlight problems with my writing and structuring to me.

no-default-kernelopts and no-nomodeset features are missing from the manpage.

Thanks @marmarek for helping me troubleshoot fedora.

[parulin]

I tested your instructions on Qubes 4.3, with a debian template. It works well, thanks!

[parulin]

Those comments are even more nitpicky. Sorry about that!

[parulin]

Not sure if I should make GUI instructions with screenshots as well or not. In this case specifically I don't like this idea because it will involve screenshots of the settings menu with just a couple of changes (that should be highlighted somehow to even find them in a settings menu screenshot), I think it will make instructions unnecessarily long. Besides, advanced users should already know things like that or be fine with CLI.

I forgot to answer that: as you said, it is for advanced users and some CLI are required, so providing a GUI way would not be very useful.

[RandyTheOtter]

I have decided to not bother with fedora autologin too too much, it is off-topic. Please tell me if there are any issues left with this pr, otherwise it should be okay to merge