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77 lines
3.0 KiB
Markdown
77 lines
3.0 KiB
Markdown
---
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layout: doc
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title: GUI Configuration and Troubleshooting
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permalink: /doc/gui-configuration-and-troubleshooting/
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redirect_from:
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- /doc/gui-configuration/
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---
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# GUI Configuration and Troubleshooting
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## Video RAM adjustment for high-resolution displays
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**Problem:** You have a 4K external display, and when you connect it, you can't click on anything but a small area in the upper-right corner.
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When a qube starts, a fixed amount of RAM is allocated to the graphics buffer called video RAM.
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This buffer needs to be at least as big as the whole desktop, accounting for all displays that are or will be connected to the machine.
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By default, it is as much as needed for the current display and an additional full HD (FHD) display (1920×1080 8 bit/channel RGBA).
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This logic fails when the machine has primary display in FHD resolution and, after starting some qubes, a 4K display is connected.
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The buffer is too small, and internal desktop resize fails.
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**Solution:** Increase the minimum size of the video RAM buffer.
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```sh
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qvm-features dom0 gui-videoram-min $(($WIDTH * $HEIGHT * 4 / 1024))
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qvm-features dom0 gui-videoram-overhead 0
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```
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Where `$WIDTH`×`$HEIGHT` is the maximum desktop size that you anticipate needing.
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For example, if you expect to use a 1080p display and a 4k display side-by-side, that is `(1920 + 3840) × 2160 × 4 / 1024 = 48600`, or slightly more than 48 MiB per qube.
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After making these adjustments, the qubes need to be restarted.
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The amount of memory allocated per qube is the maximum of:
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- `gui-videoram-min`
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- current display + `gui-videoram-overhead`
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Default overhead is about 8 MiB, which is enough for a 1080p display (see above).
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So, the `gui-videoram-overhead` zeroing is not strictly necessary; it only avoids allocating memory that will not be used.
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You might face issues when playing video, if the video is choppy instead of
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smooth display this could be because the X server doesn't work. You can use the
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Linux terminal (Ctrl-Alt-F2) after starting the virtual machine, login. You can
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look at the Xorg logs file. As an option you can have the below config as
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well present in `/etc/X11/xorg.conf.d/90-intel.conf`, depends on HD graphics
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though -
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```bash
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Section "Device"
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Identifier "Intel Graphics"
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Driver "intel"
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Option "TearFree" "true"
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EndSection
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```
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## GUI Troubleshooting
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If you can start your VM, but can't launch any applications, then you need to fix the issues from the `VM console`, accessible from xen through:
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```sh
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qvm-start <VMname> # Make sure the VM is started
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sudo xl console <VMname>
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```
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### Tips
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#### Disable audited messages
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To disable audited messages, you need to edit your VM kernel parameters:
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```sh
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previous_kernel_parameters=$(qvm-prefs --get <VMname> kernelopts) # Get current kernel parameters
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qvm-prefs --set <VMname> kernelopts "<previous_kernel_parameters> audit=0"
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```
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Then, restart your VM.
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Once your troubleshooting is done, don't forget to remove this kernel parameters, it makes troubleshooting VMs not starting easier.
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