NetBSD/Xen prompting for root filesystem although provided in boot.cfg

[Matthias Petermann <mp%petermann-it.de@localhost>]

Hello,

I am trying to multiboot my NetBSD 9.1/Xen 4.13 system with Xen and 
causes me some headache :-( It seems like the root file system is not 
automatically mounted. From the setup side, the root filesystem is 
located in a disklabel, which in turn is located on a RAIDFrame device, 
which consists of two components, each consisting of a GPT partition on 
two physical disks.

In my boot.cfg I have:

```
menu=Boot Xen:load /netbsd-XEN3_DOM0.gz bootdev=raid0a;multiboot /xen.gz 
dom0_mem=512M dom0_max_vcpus=1 dom0_vcpus_pin console=com2 com2=9600,8n1
```

but for some reason the Kernel still prompts for the root device, the 
dump device, file system and later for the init location. Anyway, the 
provided defaults are correct and could be used right away. Thats why it 
needs currently manual intervention on every boot:

```
[   3.3500231] raid0: RAID Level 1
[   3.3500231] raid0: Components: /dev/dk0 /dev/dk1
[   3.3500231] raid0: Total Sectors: 234434432 (114469 MB)
[   3.3500231] WARNING: 1 error while detecting hardware; check system log.
[   3.3500231] boot device: raid0
[   3.3500231] unknown device major 0xffffffffffffffff
[   3.3500231] root device (default raid0a):
[   3.4089966] dump device (default raid0b):
[   3.9617492] file system (default generic):
...
```

In the case above it is sufficient to take over the defaults by simply 
pressing the enter key. The system will boot without any problem after 
this. But of course, the manual intervention is inappropriate for a 
production system.

I did some further experiments and found out when I omit the bootdev 
parameter in boot.cfg, dk0 is offered as the default for the root 
device. dk0 is the GPT partition of one of the raid frame components on 
which the root file system is based. Logically this doesn't qualify as a 
valid root filesystem and fails booting.

So the bootdev parameter already seems to have some effect - namely to 
set the defaults accordingly. I am just wondering why I am still being 
asked, although everything is actually known...

From what I've seen, it reminds me a bit of my similar topic from 
August 2018[1].

Can anyone give me a hint as to what I am doing wrong?

Kind regards
Matthias

[1] http://mail-index.netbsd.org/port-xen/2018/08/23/msg009290.html