From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jesper Juhl Subject: Re: [PATCH v2 -mm 4/9] netconsole: Add some useful tips to documentation Date: Tue, 10 Jul 2007 14:34:39 +0200 Message-ID: <200707101434.39938.jesper.juhl@gmail.com> References: <20070710091920.23907.96483.sendpatchset@cselinux1.cse.iitk.ac.in> <20070710091941.23907.45658.sendpatchset@cselinux1.cse.iitk.ac.in> <20070710094142.GM11115@waste.org> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Cc: Satyam Sharma , Linux Kernel Mailing List , Keiichi Kii , Netdev , Joel Becker , Stephen Hemminger , Andrew Morton , David Miller , Jesper Juhl To: Matt Mackall Return-path: Received: from ug-out-1314.google.com ([66.249.92.175]:50821 "EHLO ug-out-1314.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752420AbXGJMfJ (ORCPT ); Tue, 10 Jul 2007 08:35:09 -0400 Received: by ug-out-1314.google.com with SMTP id j3so1315247ugf for ; Tue, 10 Jul 2007 05:35:08 -0700 (PDT) In-Reply-To: <20070710094142.GM11115@waste.org> Content-Disposition: inline Sender: netdev-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On Tuesday 10 July 2007 11:41:43 Matt Mackall wrote: > On Tue, Jul 10, 2007 at 02:49:41PM +0530, Satyam Sharma wrote: > > From: Satyam Sharma > > > > [4/9] netconsole: Add some useful tips to documentation > > > > Add some useful general-purpose tips. > > > > Signed-off-by: Satyam Sharma > > Cc: Keiichi Kii > > Acked-by: Matt Mackall > > As long as we're on the subject, I've been meaning to add a note > telling people to set their console log level to something useful, as > having that set too low is the most common problem people encounter. How about this? From: Satyam Sharma Add some useful general-purpose tips. Signed-off-by: Satyam Sharma Cc: Keiichi Kii Acked-by: Matt Mackall Signed-off-by: Jesper Juhl --- Documentation/networking/netconsole.txt | 18 ++++++++++++++++++ 1 files changed, 18 insertions(+), 0 deletions(-) diff --git a/Documentation/networking/netconsole.txt b/Documentation/networking/netconsole.txt index 1caa6c7..ffd5058 100644 --- a/Documentation/networking/netconsole.txt +++ b/Documentation/networking/netconsole.txt @@ -44,11 +44,29 @@ WARNING: the default target ethernet setting uses the broadcast ethernet address to send packets, which can cause increased load on other systems on the same ethernet segment. +TIP: some LAN switches may be configured to suppress ethernet broadcasts +so it is advised to explicitly specify the remote agents' MAC addresses +from the config parameters passed to netconsole. + +TIP: to find out the MAC address of, say, 10.0.0.2, you may try using: + + ping -c 1 10.0.0.2 ; /sbin/arp -n | grep 10.0.0.2 + +TIP: in case the remote logging agent is on a separate LAN subnet than +the sender, it is suggested to try specifying the MAC address of the +default gateway (you may use /sbin/route -n to find it out) as the +remote MAC address instead. + NOTE: the network device (eth1 in the above case) can run any kind of other network traffic, netconsole is not intrusive. Netconsole might cause slight delays in other traffic if the volume of kernel messages is high, but should have no other impact. +Some people forget to raise the kernels log_level to an +appropriate level and thus don't see all the kernel log messages they +expect. You can add the kernel boot option "ignore_loglevel" to see all +messages or you can use SysRq to set the log level to a specific value. + Netconsole was designed to be as instantaneous as possible, to enable the logging of even the most critical kernel bugs. It works from IRQ contexts as well, and does not enable interrupts while