How to enter DDB through a terminal server / remote console ...
?
Robert Watson
rwatson at FreeBSD.org
Wed Jun 28 23:54:04 UTC 2006
On Wed, 28 Jun 2006, User Freebsd wrote:
> On Wed, 28 Jun 2006, Robert Watson wrote:
>
>> On Wed, 28 Jun 2006, User Freebsd wrote:
>>
>>> 'k, now that I'm up to 3 6-STABLE servers that are deadlocking, I'm
>>> spending time with the remote tech today to get a serial console put
>>> online ... how do I drop into DDB remotely, where the serial console is
>>> going through a Portmaster Terminal server? issuing CTL-ALT-ESC, I doubt,
>>> will work, will it?
>>
>> If configured to use a serial console (console="comconsole" in
>> loader.conf), you can enter the debugger with BREAK_TO_DEBUGGER in the
>> kernel config by sending a serial break. With my portmasters, I telnet to
>> a TCP port to connect to the serial console, so I send a telnet break,
>> using ^]send break.
>
> Have you ever had a problem with this warning: "(useful for remote
> diagnostics, but also dangerous if you generate a spurious BREAK on the
> serial port!)" in the handbook?
Yes. It's unusual, but once in a while I get a nervous serial port. If you
experience this, type "Cont" to continue, and then recompile your kernel with
ALT_BREAK_TO_DEBUGGER but without BREAK_TO_DEBUGGER. Here's the notes entry:
# Solaris implements a new BREAK which is initiated by a character
# sequence CR ~ ^b which is similar to a familiar pattern used on
# Sun servers by the Remote Console.
options ALT_BREAK_TO_DEBUGGER
I've not had problem a problem on any recent hardware except for my soekris.
Robert N M Watson
Computer Laboratory
University of Cambridge
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