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Date: Thu, 02 Aug 2012 22:39:28 +0200 From: Dirk Gouders <gouders@...bocholt.fh-gelsenkirchen.de> To: Rob Landley <rob@...dley.net> Cc: Milton Miller <miltonm@....com>, Borislav Petkov <bp@...en8.de>, Cong Wang <xiyou.wangcong@...il.com>, Jesse Barnes <jbarnes@...tuousgeek.org>, Jan Engelhardt <jengelh@...i.de>, Linux Kernel <linux-kernel@...r.kernel.org> Subject: Re: [RFC] netconsole.txt: "nc" needs "-p" to specify the listening port Dirk Gouders <gouders@...bocholt.fh-gelsenkirchen.de> writes: > Rob Landley <rob@...dley.net> writes: > >> On 07/29/2012 03:40 AM, Milton Miller wrote: >>> [adding Rob as Doc maintanier] >>> >>> On Sat, 28 Jul 2012 about 11:08:16 -0000, Dirk Gouders wrote: >>>> Borislav Petkov <bp@...en8.de> writes: >>>> >>>>> On Fri, Jul 27, 2012 at 11:24:53AM +0200, Dirk Gouders wrote: >>>>>> Cong Wang <xiyou.wangcong@...il.com> writes: >>>>>> >>>>>>> On Fri, Jul 27, 2012 at 2:35 PM, Dirk Gouders >>>>>>> <gouders@...bocholt.fh-gelsenkirchen.de> wrote: >>>>>>>> Hi Jesse, >>>>>>>> >>>>>>>> I would like to ask you to check if the documentation of "nc" in >>>>>>>> netconsole.txt is still correct. I tried two different netcat packages >>>>>>>> and both require "-p" to specify the listening port. I am wondering if >>>>>>>> that changed after the use of "nc" has been documented. >>>>>>> >>>>>>> On Fedora 16, `nc -u -l <port number>` works fine. >>>>>> >>>>>> Thanks for checking that. >>>>>> >>>>>> If the information I found is correct, Fedora uses OpenBSD's nc >>>>>> codebase. The two netcat packages I tested on a Gentoo system differ in >>>>>> requiring the -p switch for the port specification. >>>>> >>>>> So say exactly that in the doc: that the *BSD's version of nc doesn't >>>>> need the port number specified with '-p' and you're covered. >>>> OK, I tried that in the attached patch. >>>> I'm not sure if every exeption needs to/should be documented, though. >>>> >>>> >From 3cdeac3e814471053129145c5fa8391acb365fd8 Mon Sep 17 00:00:00 2001 >>>> From: Dirk Gouders <gouders@...bocholt.fh-gelsenkirchen.de> >>>> Date: Sat, 28 Jul 2012 12:32:49 +0200 >>>> Subject: [PATCH] netconsole.txt: non-BSD versions of nc(1) require '-p' >>>> switch >>>> >>>> Gentoo for example uses non-BSD versions of nc(1) which require >>>> the '-p' switch to specify the listening port. >>>> >>>> --- >>>> Documentation/networking/netconsole.txt | 3 ++- >>>> 1 files changed, 2 insertions(+), 1 deletions(-) >> >> Did this ever resolve to a specific recommended patch? The one at the >> start of the thread: >> >> http://lkml.indiana.edu/hypermail/linux/kernel/1207.3/01995.html >> >> Apparently isn't it...? > > Sorry for the delay. > I tested the situation on a few distributions and am still thinking > about a proper way to write it in a way without netconsole.txt becoming > a kind of "netcat.txt". > > I would be glad about comments to what I currently have -- also, because > I am not a native English speaker: > > ------------------------------------------------------------------------ > The remote host can run syslogd or netcat to receive the kernel > messages. On distributions using a BSD-based netcat version > (e.g. Fedora, openSUSE and Ubuntu) the listening port must be > specified without the -p switch: > > 'nc -u -l -p <port>' / 'nc -u -l <port>' or > 'netcat -u -l -p <port>' / 'netcat -u -l <port>' > ------------------------------------------------------------------------ > > At the end, I also attach what I have noted during the tests with the > different distributions. > > Dirk > > ------------------------------------------------------------------------ > Problem on systems where the gnu-netcat package provides a symbolic > link /usr/bin/nc -> /usr/bin/netcat: > > gnu-netcat requires -p to specify the local port but does not complain > if invoked as `nc -l -u <port>'; you need to use -v to see that it > does not do what you might expect: > > # nc -l -u 4444 -v > Warning: Inverse name lookup failed for `0.0.17.92' > ------------------------------------------------------------------------ > > Distro Package needs -p > Command invocation > ======================================================================== > Arch gnu-netcat yes > (Website nc | netcat > documentation) > openbsd-netcat no > nc.openbsd > ------------------------------------------------------------------------ > Debian-6.0.5 netcat-openbsd no > nc | netcat | nc.openbsd > > netcat / netcat-traditional (preinstalled) yes > nc | netcat > > netcat6 yes > nc | netcat | nc6 > ------------------------------------------------------------------------ > Fedora-17 nc (preinstalled) no > nc > > nc6 > nc6 yes > ------------------------------------------------------------------------ > Gentoo gnu-netcat yes > netcat > > netcat yes > nc > > netcat6 yes > nc | nc6 > ------------------------------------------------------------------------ > OpenSUSE-12.1 netcat-openbsd no > nc | netcat > ------------------------------------------------------------------------ > Ubuntu-12.04 netcat-openbsd (preinstalled) no > Desktop nc | netcat | nc.openbsd > > netcat / netcat-traditional yes > nc | netcat > > netcat6 yes > nc | netcat | nc6 > ------------------------------------------------------------------------ Here is a patch that also includes Jan's suggestion for socat(1). The problem with the patch is that the netcat part does not cover every possible distribution/netcat-package situation but in my opinion it is a bearable compromise with respect to keeping the example section compact. Dirk >From d756d2750e4cf07d3c0942dc3c491d57631d4338 Mon Sep 17 00:00:00 2001 From: Dirk Gouders <gouders@...bocholt.fh-gelsenkirchen.de> Date: Thu, 2 Aug 2012 22:20:16 +0200 Subject: [PATCH] netconsole.txt: revision of examples for the receiver of kernel messages There are at least 4 implementations of netcat with the BSD-based being the only one that has to be used without the -p switch to specify the listening port. Jan Engelhardt suggested to add an example for socat(1). --- Documentation/networking/netconsole.txt | 19 +++++++++++++++++-- 1 files changed, 17 insertions(+), 2 deletions(-) diff --git a/Documentation/networking/netconsole.txt b/Documentation/networking/netconsole.txt index 8d02207..2e9e0ae2 100644 --- a/Documentation/networking/netconsole.txt +++ b/Documentation/networking/netconsole.txt @@ -51,8 +51,23 @@ Built-in netconsole starts immediately after the TCP stack is initialized and attempts to bring up the supplied dev at the supplied address. -The remote host can run either 'netcat -u -l -p <port>', -'nc -l -u <port>' or syslogd. +The remote host has several options to receive the kernel messages, +for example: + +1) syslogd + +2) netcat + + On distributions using a BSD-based netcat version (e.g. Fedora, + openSUSE and Ubuntu) the listening port must be specified without + the -p switch: + + 'nc -u -l -p <port>' / 'nc -u -l <port>' or + 'netcat -u -l -p <port>' / 'netcat -u -l <port>' + +3) socat + + 'socat udp-recv:<port> -' Dynamic reconfiguration: ======================== -- 1.7.8.6 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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