[Udpcast] Cloning Live Machine

Alain Knaff alain at knaff.lu
Wed Jul 21 13:45:50 CEST 2004

On Wednesday 21 July 2004 12:52, Lee Kransen wrote:
> The machine I need to copy will be totally idle, except for normal system
> activity, with no active users, connections or intentionally running
> programs. The reason I thought to do it "live" is that the machine has no
> CD or diskette drive and not even a USB port. I need to update the machine
> every few days with the newest version of our system and then copy it to
> several 10's of new machines.
> If I understand correctly, it seems that the best option is for me to take
> out the hard drive, put it in the DHCP/TFTP server and run the udp-sender
> from there. Is that correct?

That's one possibility.

Other possibilities include:

 1. Booting udpsender from network (DHCP) on that machine
 2. or, Putting udpcast's kernel and initrd on the machine, and set up a
 lilo (or grub) entry to boot that.
 3. or, Do the udpcast "live" anyways, but from a low runlevel (1), with
 root fs unmounted. As the FS is unmounted, the system is not really
 live as far as udpcast is concerned...

> If I decide to copy the disk to an image file and want to zero-ize the
> empty part of the drive, I understand that I can do this with dd. Could you
> tell me the command?

On the live system, just create a huge file:

dd if=/dev/zero of=filler-file

After a while, the dd will error out with a "disk full" error.

Then, do a couple of syncs, and remove the file.

rm filler-file

> If I want to use lzop or gzip to UDPCast a saved image, do I have to save
> the image in the appropriate compressed format before the transfer or does
> UDPCast compress a saved image file on the fly during transfer?
> Thanks a bunch,
> Lee

Udpcast is able to compress the file on the fly (using the -p flag),
after all, that's how the bootable udpsender does it.

However, if you keep images on the server, it's best to precrompress
them on the server for two reasons:
 1. Space saving (obvious...)
 2. CPU time & disk read time saving (may lead to a faster transfer,
    esp for those long stretches of zeroes)


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