Messages in this thread | | | From | Dirk Gouders <> | Subject | Re: [RFC] netconsole.txt: "nc" needs "-p" to specify the listening port | Date | Wed, 01 Aug 2012 17:46:38 +0200 |
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Rob Landley <rob@landley.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@alien8.de> writes: >>> >>>> On Fri, Jul 27, 2012 at 11:24:53AM +0200, Dirk Gouders wrote: >>>>> Cong Wang <xiyou.wangcong@gmail.com> writes: >>>>> >>>>>> On Fri, Jul 27, 2012 at 2:35 PM, Dirk Gouders >>>>>> <gouders@et.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@et.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 ------------------------------------------------------------------------
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