From owner-freebsd-current@FreeBSD.ORG Tue Sep 16 18:27:27 2003 Return-Path: Delivered-To: freebsd-current@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 6D68D16A4C4 for ; Tue, 16 Sep 2003 18:27:27 -0700 (PDT) Received: from mailman.zeta.org.au (mailman.zeta.org.au [203.26.10.16]) by mx1.FreeBSD.org (Postfix) with ESMTP id B149F43FBF for ; Tue, 16 Sep 2003 18:27:25 -0700 (PDT) (envelope-from bde@zeta.org.au) Received: from gamplex.bde.org (katana.zip.com.au [61.8.7.246]) by mailman.zeta.org.au (8.9.3p2/8.8.7) with ESMTP id LAA03153; Wed, 17 Sep 2003 11:27:17 +1000 Date: Wed, 17 Sep 2003 11:25:54 +1000 (EST) From: Bruce Evans X-X-Sender: bde@gamplex.bde.org To: Don Bowman In-Reply-To: Message-ID: <20030917111259.C7949@gamplex.bde.org> References: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII cc: "'freebsd-current@freebsd.org'" Subject: Re: using tip on machine that has COMCONSOLE set to serial X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 17 Sep 2003 01:27:27 -0000 On Tue, 16 Sep 2003, Don Bowman wrote: > This may be a dumb question, but I have > a situation where machine A and B both have > enabled serial console. I'm ssh'ing into A to > try and debug a problem on B. I'm trying to > use tip, but am getting interference from the > fact that A also has a serial console. > > If i disable the getty, its a bit better. > > Is there a way to make this work reliably, or > am I SOL? Not completely reliably. In -current you can try switching off the serial console, but IIRC the switching code has problems in precisely this area -- it doesn't turn off the lowest levels of consoleness. Turning off getty is a good idea. cua* with getty on ttyd* may work, but it is necessary to turn off CLOCAL on the console snd maybe fiddle with carrider on the line so that getty blocks in open. CLOCAL defaults to on for serial consoles and is locked on. Speeds are also locked for consoles. Turning off anything that writes to the console (e.g., syslogd) is a good idea if you haven't turned off the console. I sometimes turn off low level writes by writing machine code in ddb. On i386's, writing byte 0xc3 at printf turns off all kernel printfs (fortunately nothing checks their return value :-). Overwriting byte 0xe8 with byte 0xb8 in calls to printf turns off individual printfs. Bruce