PXE boot loads wrong disk after OS installation

Users
1

Hello everyone,

I am using MAAS 3.5.7 in a lab environment.
The servers’ power driver is a webhook (probably irrelevant to the issue).

Each server has two disks:

  • /dev/nvme0n1 — NVMe disk (target for OS installation)
  • /dev/sda — SATA disk (not marked as boot and with no partitions)

The operating system is correctly installed on /dev/nvme0n1.
The /dev/sda disk is not marked as boot and has no partitions, as shown in the MAAS Storage screen:

image
image1637×708 98.4 KB

The BIOS boot order is set to:

  1. PXE
  2. NVMe disk

Expected behavior:
After OS installation, PXE should fall back to booting from /dev/nvme0n1, which is marked as the boot disk in MAAS.

Observed behavior:
After the OS is installed and the system reboots, the server starts via PXE.
PXE then displays something like “booting from local disk” and loads /dev/sda instead of /dev/nvme0n1.

This results in an endless boot loop, as the SATA disk has no valid OS.

To confirm the issue, I manually installed FreeDOS on /dev/sda. After reinstalling the OS via MAAS, PXE booted into FreeDOS — proving that the PXE fallback is loading the wrong disk.

image
image1407×751 89 KB

Notes:

  • If I manually change the boot device in BIOS to the NVMe disk, the OS installed by MAAS boots successfully.
  • This suggests that the PXE boot script used by MAAS may be selecting the first disk detected by firmware (/dev/sda) instead of the disk marked as boot disk in MAAS.

Question:
Is there any known workaround for this behavior?
Or is this a known bug in the PXE fallback logic in MAAS?

2

Did you deploy vanilla ubuntu or a custom image?

3

@r00ta vanilla image, ubuntu 24.04 with and without hwe kernel. Same behaviour.

4

This is weird according to your screenshot. MAAS should have wiped that disk, so you would not boot into that OS

5

@r00ta
I’m looking for PXE menus and found this template.
I guess this template shows what is happening…

cat config.local.amd64.template  
DEFAULT local  
  
LABEL local  
  SAY Booting local disk ...  
  KERNEL chain.c32  
  APPEND hd0

here: APPEND hd0

Could it be that hd0 refers to the first disk the BIOS recognizes as hd0, and not necessarily the disk MAAS considers the bootable disk?

6

This is indeed an odd issue. What happens if you remove the sda disk entirely from the machine’s config?

8

If I physically remove the disk from the server, everything works, but the extra disk configuration still remains in MAAS’s storage settings.
If I keep the disk plugged in but remove it from the storage configuration, the issue persists it still tries to boot from the first disk (in this case, sda).