Subject: kern/24405: ddb(4) should mention hw.cnmagic
To: None <>
From: Christian Biere <>
List: netbsd-bugs
Date: 02/12/2004 22:40:43
>Number:         24405
>Category:       kern
>Synopsis:       ddb(4) should mention hw.cnmagic
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    kern-bug-people
>State:          open
>Class:          change-request
>Submitter-Id:   net
>Arrival-Date:   Thu Feb 12 22:41:00 UTC 2004
>Originator:     Christian Biere
>Release:        NetBSD 1.6ZJ
System: NetBSD Cyclonus 1.6ZJ NetBSD 1.6ZJ (STARSCREAM) #3: Wed Feb 11 11:27:20 CET 2004 root@Cyclonus:/usr/src/sys/arch/i386/compile/STARSCREAM i386
The documentation for ddb(4) mentions a mysterious ``break'' key to
activate ddb from a serial console. My terminal has such a key but it's
supposed to break out of the terminal mode. It doesn't send anything
on the wire. Fortunately, Google lead me to a post of a clever guy who
knew about ``hw.cnmagic''. This should really be mentioned in ddb's
manpage because this information is hard to find and some terminals
might not have the mysterious ``break'' key or it serves a different

Maybe cnmagic(9) should be referenced, too. Nice to know,
not sure whether it matters here.


Index: ddb.4
RCS file: /cvsroot/src/share/man/man4/ddb.4,v
retrieving revision 1.76
diff -u -r1.76 ddb.4
--- ddb.4	2003/12/14 09:40:07	1.76
+++ ddb.4	2004/02/12 22:28:51
@@ -153,6 +153,16 @@
 Interrupt switch on the body.
+The key sequence to activate
+can be changed by modifying
+.Dq "hw.cnmagic"
+.Xr sysctl 8 .
+If the console is not dedicated to
+the sequence should not be easily typed by accident.
 In addition,
 may be explicitly activated by the debugging code in the kernel