From mboxrd@z Thu Jan 1 00:00:00 1970 From: Neil Horman Subject: Re: netconsole fun Date: Mon, 17 Dec 2012 09:20:30 -0500 Message-ID: <20121217142030.GB25322@hmsreliant.think-freely.org> References: <20121211164526.GB7481@neilslaptop.think-freely.org> <1355345957.2687.18.camel@thor> <20121213123611.GA12269@hmsreliant.think-freely.org> <1355410171.2605.17.camel@thor> <20121213180815.GA14796@hmsreliant.think-freely.org> <1355426821.2612.16.camel@thor> <20121213211754.GC14796@hmsreliant.think-freely.org> <1355437480.2612.33.camel@thor> <20121214142018.GA24846@shamino.rdu.redhat.com> <1355580838.2467.39.camel@thor> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Cong Wang , netdev@vger.kernel.org To: Peter Hurley Return-path: Received: from charlotte.tuxdriver.com ([70.61.120.58]:36370 "EHLO smtp.tuxdriver.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752557Ab2LQOUh (ORCPT ); Mon, 17 Dec 2012 09:20:37 -0500 Content-Disposition: inline In-Reply-To: <1355580838.2467.39.camel@thor> Sender: netdev-owner@vger.kernel.org List-ID: On Sat, Dec 15, 2012 at 09:13:58AM -0500, Peter Hurley wrote: > On Fri, 2012-12-14 at 09:20 -0500, Neil Horman wrote: > > Ah! I'm sorry, I didn't realize this was really about getting netconsole up > > early in the boot, rather than just getting it up robustly using the startup > > script. > > Well, it's both but I should have been clearer here. Sorry about that. > > > If thats the case, then I would recommend that you modify the initramfs > > to do something simmilar to the startup script (since thats where the netconsole > > module will get loaded anyway). You can write a script there that will let you > > specify the destination ip address and figure out the output dev based on the > > routing tables. If you're using dracut to build your initramfs, then this > > should be pretty straightforward. > > When I get some more free time I'll experiment with this approach. > > Just to clarify something from earlier in the discussion: > > On Thu, 2012-12-13 at 13:08 -0500, Neil Horman wrote: > > On Thu, Dec 13, 2012 at 09:49:31AM -0500, Peter Hurley wrote: > .... > > > There is an unforeseen consequence of the patch: it breaks device > > > renaming because the device will already be in use by netconsole. Which > > > is the whole problem with userspace device renaming to begin with... > > > > > That is bad, but see above, the netconsole service can work around this for you, > > allowing you to never have to specify a particular device at all. > > The breakage is a normal consequence of being able to load netconsole > before the udev rules that do device renaming. The same thing would > happen modifying initramfs. > > Basically, once netconsole attaches to a device, that device cannot be > renamed. Unfortunately, the default udev behavior messes things up > further because it will try to do this: > eth0->eth1 > eth1->eth0 > which means neither device will be renamed. > > Maybe the net core should just implement persistent device names ;) > Theres no good way for the kernel to do that, as persistent naming in this case is a matter of user policy, not kernel hardware management (i.e. do you want a network name to follow a mac address, a pci slot, or the network its connected to)? You can use smbios to get some modicum of persistent device naming currently, but I don't recall if that requires udev rules to implement as well You're best bet is to simply make your initramfs more robust. I understand what you're saying regarding renaming after you've taken a reference on a device not being possible, but you can run udev within the initramfs, and do your renaming prior to your netconsole load. Thanks Neil > Thanks again for all your time, > Peter Hurley > >