[Udpcast] newbie questions:

James Tipler james.tipler at stcatz.ox.ac.uk
Fri Mar 14 09:43:26 CET 2008

Thanks for replying so fast! 

Actually, you're point about the switch is spot on. It's a 3com, and
spending a few minutes poking around in it's config last night sorted
everything out -  should have checked it before posting here really! 

Thanks again. 

-----Original Message-----
From: Michael D. Setzer II [mailto:mikes at kuentos.guam.net] 
Sent: 13 March 2008 22:49
To: James Tipler; udpcast at udpcast.linux.lu
Subject: Re: [Udpcast] newbie questions:

On 13 Mar 2008 at 15:43, James Tipler wrote:

> Hi, I apologize if this is a stupid question - actually, I rather hope it
is because if I've just missed 
> something somewhere in the documentation then this should be easy to sort
> I've got about 30 work stations here that are used by conferences a dozen
or so times a year. 
> Each time they come in they manage to make a mess of them in one way or
another, so each 
> workstation gets re-imaged once they've gone away. Currently, we do this
with a little linux 
> partition with G4L on it and a little tweaking of the Windows NT boot
loader. (Basically, run batch 
> file in windows - machine goes down, linux comes up, script runs, disk
image.gz is pulled from 
> FTP server and written to the windows partition, machine goes down,
windows comes up, 
> job'sagood'un)
> This works rather nicely, but it takes a painfully long time as the FTP
server struggles under the 
> load of 30 connections. UDP-cast looks perfect for solving this problem,
but I can't seem to make 
> it work. This is the command I've got:
> (from the FTP server -windows 2003 machine)
> Udp-sender.exe -file c:\bootfiles\image.gz
> (from the client machines linux command line)
> Udp-receiver -pipe "gzip -dc" -file /dev/sda1
> The network infrastructure is very simple. All the machines involved are
in the same subnet 
> 129.67.50.xx (in fact they're all on the same switch to try and keep this
as fast as possible)
> The UDP sender starts to run and awaits connections, but never seems to
get any.
> The UDP receivers sit and wait for a control connection from the server,
but never get any either.
> What am I doing wrong?

Not a 100% sure? But here are some things. 
First off, what kind of switch do you have? I had no problems with my old 
hubs, then MIS replaced them with 3COM switches, and udpcast stopped 
working. It would work with a single set of machine, but not multiple.
out to be an IGMP setting if I recall correctly.

Second, what does it say exactly it show on the sender and reciever screens 
concerning the multicast-

G4L does have the option to receive udpcast, and checking the lines, with 
lzop compression it is `lzop -d -c -`    and with gzip it shows `gzip -c - `
that is with linux, and it might just be the difference in how windows does
So, it could just be the missing -. 

Being the mainter of G4L, it make use of udpcast every week. I generally 
make updates to my lab machines, and create a new g4l backup image, and 
the use udpcast to image all the other machines in the lab. So, one ftp 
download to a sinfle machine, and then multi-cast to all the others. I
a custome udpcast send disk, and 7 copies of a udp-recieve disk. Just put 
the sender disk in the one machine, and it has all options set, and is ready
go. Then boot other machines from the reciever disk, and then hit enter on 
any machine went all are ready. I setup these CDs to do a whole disk image, 
so no inputed needed at all. Works just great.

Another options. In my lab, the XP partition is always get messed up or 
changes, and we were recently getting this kavo virus being spread by 
flahes, and Norton was not stopping it at all. In this case, my XP partition

imagge is about 6GB, so I just copied it to the Linux partition, which is
of the 80GB drive. So, it had plenty of free space. I then have it do a
ntfsclone restore to the XP partition, and can reimage the windows in about 
10 minutes. NTFSCLONE is faster, since it only copies used data, and by 
not downloadin the image to all machines at once puts no load on the 

So, thre are some things to look at.

  Michael D. Setzer II -  Computer Science Instructor      
  Guam Community College  Computer Center                  
  mailto:mikes at kuentos.guam.net                            
  mailto:msetzerii at gmail.com
  Guam - Where America's Day Begins                        

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