There have been a few issues with Qubes tools since I’ve been using Qubes, aka a few years. I don’t know why it happens, but it happens with moderate frequency. It seems to be cross-app, and to do with the Qubes tools themselves. Because of what I assume to be dom0 CPU usage, all Qubes tools freeze (Qubes Manager, Backup/Restore, Domains Widget, Devices Widget, and Storage Widget confirmed, others unknown). While frozen, they are unresponsive, and if one switches to another virtual desktop and back, that virtual desktop is shown in the border of the Qubes tool, whether it be the background image or another app. (You cannot interact with the app within the dom0 border as far as I can tell.)
This could be a vulnerablity. Could a malicious VM launch disposables and crash dom0 or the Qubes tools? It’s never happened to me, they always unfreeze, but it’s concerning.
I have not noticed such problems with Dom0, but it sounds familiar from other Fedora instances.
The journalctl command may help you to find the cause. It has options to decrease the amount of output. For example, something like: sudo journalctl -p 0..3 (Edited: Note that it is not ’ -p 0-3 ’ )
should show only “bad” events, not information messages. You can search for the time of the event.
During the event, you can probably(?) switch to text console using Ctrl-Alt-F3 keys, login, and try running top command. It mat show a problem process.
My experience of Fedora has been:
“oom” events - insufficient memory or runaway process
“abrt” handling of failed processes
Occasional housekeeping processes that use a lot of resources (not so likely in Dom0?)
If you can provide more information, then maybe it can be solved, and can help others. For example, Qubes version, other activity, etc
It doesn’t seem to be limited to any version or hardware. I’ve personally observed it on 4.1, 4.2, and 4.3 on several different Intel-based motherboards.
How to reproduce:
Start several qubes. This may depend on your hardware, but 8 works for me. (All 8 are 2 vcpus and 500MB memory without qmemman)
Try to use a Qubes app (Qubes manager, tray apps/widgets, qubes backup, qubes restore, etc.
Expected behavior: VMs cannot affect qubes apps
Actual behavior: all apps are unresponsive, and ones in a window will show the contents of the last virtual desktop you were on, until the qubes finish booting/shutting down.
I couldn’t find anything in top common across two different systems, and nothing of note in logs.
So, as it turns out you only need one qube to reproduce when starting, and you don’t even have to restart it. Try setting sys-usb to 1 core and 300MB and restart it. It will hang for a second or two. It also works by launching the qube settings for more than one qube at a time.