Dualboot VM

[Tim Denis]

I have a PVE 8 running. One of the VM's is my 'daily driver'. A Nvidia dGPU is passed trough to that VM, along with USB hosts, and I'm running a dual monitor setup and the needed USB devices. Runs Win11. Works great for many months now.

However, I'm looking to experiment with fedora as my daily driver. I can easily attach another (virtual) disk to that machine and install fedora on that disk, and 'change' the disks whenever I want to boot to either Win11 or fedora. But this sounds error prone and a recipie for disaster. I'm in favor of leaving my win11 install in place and robuust, so installing a dual boot on that disk is not what I want.

Is there a way to quickly and reliable switch the main virtual disk?
- start the vm (could be commandline?) with a parameter, or use a script to do something and as a last command 'qm start ...'
- have proxmox halt on booting that VM, and make me choose which disk to boot from
- ...?

Ideas appreciated!

 

[bbgeek17]

Have you considered just adding new VM?

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Blockbridge : Ultra low latency all-NVME shared storage for Proxmox - https://www.blockbridge.com/proxmox

 

[Tim Denis]

Yes, I did, but then I would have continously swicth the passtrough of the dGPU and USB hosts to the other machines as well. Sounds even more cumbersome and error prone...

 

[bbgeek17]

I am not an expert in passthrough, but wouldn't you just configure same exact passthrough devices in both VMs and just use it one at a time - same if you jury-rigged a dual boot VM?

---

Blockbridge : Ultra low latency all-NVME shared storage for Proxmox - https://www.blockbridge.com/proxmox

 

[leesteken]

Yes, I did, but then I would have continously swicth the passtrough of the dGPU and USB hosts to the other machines as well. Sounds even more cumbersome and error prone...

I am not an expert in passthrough, but wouldn't you just configure same exact passthrough devices in both VMs and just use it one at a time - same if you jury-rigged a dual boot VM?

It's not like you could run both at the same time when dual booting. You can configure both VM with the same GPU passthrough, you just can't run both at the same time. With a hookscript, you can shutdown the other one automatically when starting a VM. I do this with my Linux and Windows gaming VMs. When I want to switch, I just start the other one and wait a few tens of seconds.

 

[Dunuin]

It's not like you could run both at the same time when dual booting. You can configure both VM with the same GPU passthrough, you just can't run both at the same time. With a hookscript, you can shutdown the other one automatically when starting a VM. I do this with my Linux and Windows gaming VMs. When I want to switch, I just start the other one and wait a few tens of seconds.

Jup, works fine here. Just keep in mind that a backup job can't backup the other VM if one of them is already running. I created a vzdump hook script which will shutdown a running VM and start it again after the backup job has finished so both can be backed up.

 

[Tim Denis]

okay, thanks for all the replies. I'm gonna see which route I'll take.
The disadvantage of a seconds vm, but with shared dGPU is that disks are not available in the other vm.
I'll see what I can adapt.

 

[leesteken]

The disadvantage of a seconds vm, but with shared dGPU is that disks are not available in the other vm.

You could run a fileserver VM with NFS or SMB. Or you can passthrough a (virtual) disk between the two VMs, as long as you never run them at the same time!

 

[Tim Denis]

Okay, so I did some experimenting.
Posting here because it might serve others as well.
[read OP for problem description]

I added another disk to the VM, and installed fedora on it.

Strategy 1:change the 'Boot order' in the 'options' section of the PVE boots from either the windows or the fedora disk. Seems to be reliable.

Strategy 2: when booting, displaying the proxmox splash screen, press 'esc', go to 'bios', 'Boot Manager' , and choose the fedora or the windows boot manager. Acceptable steps to take to boot in either one of the machines.

I feel this solution is a bit more simple than what was suggested here. Thanks for the input!