install/41117: ddb.onpanic=0 in default sysctl.conf(5) could cause error

[tsutsui%ceres.dti.ne.jp@localhost]

>Number:         41117
>Category:       install
>Synopsis:       ddb.onpanic=0 in default sysctl.conf(5) could cause error
>Confidential:   no
>Severity:       non-critical
>Priority:       high
>Responsible:    install-manager
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Wed Apr 01 11:45:00 +0000 2009
>Originator:     Izumi Tsutsui
>Release:        NetBSD 5.0_RC3
>Organization:
>Environment:
System: NetBSD/sparc default install, but affects all ports
Architecture: sparc
Machine: sparc
>Description:
The default sysctl.conf(5) file now has an entry of "ddb.onpanic=0"
to avoid ddb prompt on running system, but that ddb.onpanic sysctl
node is only available on kernels with options DDB.

On sparc the default GENERIC kernel doesn't have options DDB,
so the above ddb.onpanic entry in sysctl.conf causes
the following error message
>> sysctl: second level name 'onpanic' in 'ddb.onpanic' is invalid
on every reboot.

>How-To-Repeat:
Install NetBSD/sparc 5.0_RC3 and boot it to multiuser.

>Fix:
There are several suggestions in source-changes-d thread:

- add an option to sysctl(8) to ignore error
  http://mail-index.NetBSD.org/source-changes-d/2009/03/29/msg000144.html

- introduce a new syntax for sysctl(8) to see if the specified node is vaild
  http://mail-index.netbsd.org/source-changes-d/2009/03/29/msg000148.html

But for 5.0 release, we might need simpler workaround.
(adding a dummy ddb.onpanic stub for !DDB case in some source?)

---
Izumi Tsutsui