conf/177217: rc.d/ddb -- squelch warning when ddb_enable=yes but DDB missing from kernel

Jeremy Chadwick jdc at
Fri Mar 22 01:20:00 UTC 2013

>Number:         177217
>Category:       conf
>Synopsis:       rc.d/ddb -- squelch warning when ddb_enable=yes but DDB missing from kernel
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    freebsd-bugs
>State:          open
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Fri Mar 22 01:20:00 UTC 2013
>Originator:     Jeremy Chadwick
>Release:        FreeBSD 9.1-STABLE amd64
System: FreeBSD icarus.home.lan 9.1-STABLE FreeBSD 9.1-STABLE #0 r248403: Sat Mar 16 20:33:01 PDT 2013 root at icarus.home.lan:/usr/obj/usr/src/sys/X7SBA_RELENG_9_amd64 amd64
	If a user has ddb_enable="yes" in rc.conf, but their kernel is
	lacking "options DDB" and friends, then the following message is
	shown during boot:

	/etc/rc.d/ddb: WARNING: failed precmd routine for ddb

	The reason is that returning 1 from inside of precmd causes rc.subr
	to emit the above warning.  Returning 0 would cause rc.subr to
	continue on and try to run /sbin/ddb, which emits even more errors.

	IMO, the simplest way to solve this dillema is to use "exit 1" and
	bail out of the rc.d script ASAP; some other rc.d scripts use this
	method as well.

	To make this fact clearer to future committers/readers, I added
	an explanation comment.  I also added use of $SYSCTL_N to be
	consistent with other scripts.

	I should note I did try getting rid of the precmd stuff and instead
	making a ddb_start() routine + doing the necessary magic, but this
	induces all sorts of edge cases/nuances relating to required_files
	and command_args and some other things.  exit 1 just seems easier.

	If someone has a better/cleaner method, I'm happy to test such.
	1. Set ddb_enable="yes" in rc.conf on a system lacking DDB support
	in the kernel

	2. Run "/etc/rc.d/ddb start"
	Patch is below, and will be available at the following URL one I
	get a PR number:{prnum}/

	Verified as working on stable/9 (r248403).

Index: etc/rc.d/ddb
--- etc/rc.d/ddb	(revision 248604)
+++ etc/rc.d/ddb	(working copy)
@@ -19,8 +19,11 @@ stop_cmd=":"
 	# Silently exit if ddb is not enabled
-	if [ -z "`sysctl -Nq debug.ddb.scripting.scripts`" ]; then
-		return 1
+	# NOTE: exit is needed here, not return, else rc.subr emits
+	# a "failed precmd routine" warning when ddb_enable="yes" is
+	# used on a system which lacks DDB support in the kernel.
+	if [ -z "`$SYSCTL_N -q debug.ddb.scripting.scripts`" ]; then
+		exit 1

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