[Help] VM fails to boot after restart – "ALERT! /dev/mapper/... does not exist"

[falconX]

Hi everyone,


I recently migrated several VMs from a Hyper-V environment to Proxmox using .vhdx disk images. Everything went fine during the migration: I converted the disks to .qcow2 using qemu-img, imported them via qm importdisk, attached them to the VMs, and all services were running perfectly.


One of these VMs hosts an internal LDAP service running on Ubuntu. It worked fine for over a week, including successful network communication, service availability, and normal operations.


However, after performing a simple reboot (following an automatic update), the VM dropped to the initramfs shell at boot with the following error:

ALERT! /dev/mapper/root-xxxx does not exist. Dropping to a shell!
In the initramfs shell:

• ls /dev/mapper only shows control
• vgchange -a y doesn't activate any volume
• lvs command is not found

From what I understand, the VM was originally using LVM and it seems something broke in the boot chain after the update.

My questions:​

1. Why did it work for a week and only broke after a restart?
2. Is there a way to repair this without rebuilding the VM?
3. What’s the best practice when importing .vhdx disks with LVM structure into Proxmox?

For now, I’ll probably rebuild this specific VM manually and migrate the service cleanly — but I would like to understand the root cause to prevent this for future VMs.


Thanks in advance for your help
Let me know if you need logs or config files!