I have been testing KDE Linux as a VM created by virt-manager, which works well. I want to verify that KDE Linux correctly supports creating and using VMs, but – within my KDE Linux VM – I’m unable to create nested virtual machines. The process fails at the stage where installation from a chosen ISO should begin, with the message:
Unable to complete install: ‘internal error: QEMU unexpectedly closed the monitor (vm=‘blivet’): 2026-08-17T14:27:00.799665Z qemu-system-x86_64: -device {“driver”:“ide-cd”,“bus”:“ide.0”,“drive”:“libvirt-1-storage”,“id”:“sata0-0-0”,“bootindex”:1}: Failed to get “consistent read” lock: Input/output error
Is another process using the image [/run/user/1000/doc/kHlDdvNnHHJoDUw29L_R5w/kubuntu-26.04-desktop-amd64.iso]?’
For what it’s worth, I am able to nest VMs in a Pop! Linux VM. I’ve searched but have found no resolution. Any advice would be welcome.
I don’t know if this will fix it, but have you tried giving the virt-manager Flatpak permissions to the directory on KDE Linux where your ISO lives, so that it can access it without mounting to /run ?
I was going to say I didn’t recall having permission issues while testing an image in a VM but by looking at it, I think I still had the ISO in the Downloads folder, which virt-manager Flatpak has default permission to (xdg-download).
So yeah, I would suggest putting the ISO in a specific folder and adding a permission to it then.
The ISO is in a folder with read access for all. The ISO itself is also fully readable. virt-manager sees the ISO as living under /run, whose permissions I cannot alter. I have tried redirecting virt-manager’s path to my home in /home but it won’t accept that. Because this all works under a non-immutable OS VM, I share the guess that permissions are involved, but your welcome responses suggest others are able to create VMs inside a KDE Linux VM.
Still stuck, but grateful for your thoughts. I’ll try moving the ISO elsewhere.
OK, I tried moving the ISO to /system (755) but experience the same problem. It seems that something else is going on.
Oh, you may be mistaking host file permissions (usual rwx stuff) with Flatpak ones. Flatpaks have another layer of permissions because the apps are sandboxed.
You can check and modify these permissions by looking in System Settings > Applications Permissions > Some app (here Virtual Machine Manager) > Manage Flatpak settings.
To be clear, I haven’t done nested virtualization.
But if you’re doing it as a means to the end of answering the question “if I install KDE Linux on bare metal, can I then create and use VMs from KDE Linux?”, then I can confirm from experience that the answer is yes.
Yes, nested virtualization is only important to me as a test of a bare-metal KDE Linux install, which will likely wait until the development process has matured further. Secondarily, it’s a learning opportunity. Perhaps someone will have more ideas to share about this. Thanks again.
I can confirm it is indeed an issue in non-nested setups as well, putting the ISO in an unauthorised folder gets it mounted as a FUSE mount in /run/ which ends up in the same error triggering.
The most straightforward way to fix this is putting the ISO somewhere in Documents (which is authorised) or if you put it elsewhere, add the access by doing:
flatpak --user override --filesystem=<path to your ISO folder>:ro org.virt_manager.virt-manager.
Note I wouldn’t recommend putting things in /system/ as it’s where the image files for KDE Linux are.