bin/49510: gpt(8) fails w/o drvctl and breaks sysinst

[martin%NetBSD.org@localhost]

>Number:         49510
>Category:       bin
>Synopsis:       gpt(8) fails w/o drvctl and breaks sysinst
>Confidential:   no
>Severity:       critical
>Priority:       high
>Responsible:    bin-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sun Dec 28 18:55:00 +0000 2014
>Originator:     Martin Husemann
>Release:        NetBSD 7.99.2
>Organization:
The NetBSD Foundation, Inc.
>Environment:
System: NetBSD night-owl.duskware.de 7.99.2 NetBSD 7.99.2 (NIGHT-OWL) #290: Mon Dec 1 12:37:01 CET 2014 martin%night-owl.duskware.de@localhost:/usr/src/sys/arch/amd64/compile/NIGHT-OWL amd64
Architecture: x86_64
Machine: amd64
>Description:

During install sysinst tries to decide wether a disk already has a GPT or
not. It basically invokes something like:

  gpt show sd1

but on kernels which do not have pseudo-device drvctl this fails in very
unintuitive ways:

gpt: drvctl: /dev/drvctl: Device not configured
gpt: unable to open device 'rsd1c': Device not configured

We need this operation to silently complete (in case of an absent GPT), or
add a new "does it exist" check operation which does - or teach sysinst to
check for a GPT "manually" by just looking at the start of the disk.

>How-To-Repeat:

Boot e.g. a VAX GENERIC kernel and do:

gpt sd0 show

>Fix:
n/a