[Wylug-help] Rsync is broken?

[Dave Hassett]

RichardA wrote:
>>On Sun, 29 Apr 2007, RichardA wrote:
>>
>>
>>>Tried again with different cables -- scp failed after 7 GB or so.
>>>
>>>All I can think of to do is to reinstall the server OS and then try
>>>a different PC. The symptoms don't point to any particular piece of
>>>hardware or software so I'll change everything I haven't already
>>>changed.

I know this is clutching at straws at this point, but you could try 
playing around with various Ethernet parameters. e.g. MTU size.

   /sbin/ifconfig eth0 mtu 1400

Also, you could try playing with other parameters, for example maximum 
TCP window sizes. See this page for a small list:

   http://proj.sunet.se/E2E/tcptune.html

The other thing I would do is get a wireshark/tcpdump trace of the 
transfer. If you ensure that you limit the capture to the first 68 bytes 
of each packet, you won't capture any data, and you should be able to 
create a manageable trace file (if you don't do that, you'll end up with 
a 7Gb trace!). You can at least then see why the connection is dropping.

The tcpdump command only captures the first 68 bytes anyway by default, 
so this should work:

   tcpdump -i eth0 -w trace.pcap host REMOTEHOST

Or this for wireshark (tshark):

   tshark -i eth0 -s 68 -w trace.pcap -f host REMOTEHOST

(Where REMOTEHOST is the name of the server you're rsyncing to. Also, 
change eth0 as appropriate.)

If you like, please e-mail me the (compressed) trace file, and I'll have 
a look. Up to you - the offer is there.

>>Reinstalling the server sounds like a sub-par idea if you ask me as
>>it'll take a while and not test much.  You've tried it with rsync and
>>scp.  Either there's a bug in a shared library between the two or the
>>kernel's the problem. I'd try rolling the kernel back to a 2.6.8 era
>>kernel and see what gives.
> 
> 
> I've just remembered that the server updates itself weekly, so a power
> outage could have rebooted it into a newer kernel (apologies for not
> mentioning this earlier, but I built it last summer and forgot all
> about it until it failed to work).
> 
>  However, I've tried scp with all four of the installed kernels
> (2.6.15-23, -26, -27 and -28) with no luck. I have all of the Aptitude
> update logs and there are no references to rsync or scp. There is a ssh
> update, but it's from October of last year and this was working until
> January.
> 
> How do I find which libraries are used by both rsync and scp?

You can use 'ldd'. That will tell you which shared libraries each uses, 
and you can then use your distro's package management tools to tell you 
which version of the libs are in use. e.g.

   dpkg -S /lib/libcrypto.so.0.x.x

Hope this help.

Many thanks,

Dave Hassett

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