[Udpcast] Cloning Live Machine

Lee Kransen lee at servision.net
Wed Jul 21 12:52:45 CEST 2004


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?

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?

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

-----Original Message-----
From: udpcast-bounces at udpcast.linux.lu
[mailto:udpcast-bounces at udpcast.linux.lu] On Behalf Of Felix Rauch
Sent: Wednesday, July 21, 2004 1:58 AM
To: Donald Teed
Cc: udpcast at udpcast.linux.lu
Subject: Re: [Udpcast] Cloning Live Machine

On Tue, 20 Jul 2004, Donald Teed wrote:
> On Tue, 20 Jul 2004, Christopher Curtis wrote:
>> Actually, in practice, you'll probably find that most of the time it
>> "just works".  However, if you have LVM installed, you could make a
>> snapshot of the image before you udpcast it.  Most of the data that's
>> not written to disk is "inoccuous" stuff such as logfiles.  However, I
>> wouldn't try this to make a copy of a running database, for instance.
>
> Yes, this is what I am assuming.  If the person states that
> the system must be live, it must be a production system of
> some type, providing an essential service that is accessed
> at all times of the day.  There is a good possibility of files
> being in a state of being half written, and so on.

[...]

> A database is a easy example to understand, but the same
> could be true of any file that is being written on the
> system, including the filesystem table!  Unless you are
> just fooling around, don't do it!

I had a few occasions where I had to clone a life machine,
e.g. because there was no place to store the image to and I needed to
have a bootable system on a second machine, or just because I was too
lazy to create an image first. As has been said before, most of the
time it works fine, but the cloned machine will go through a
file-system check during its first boot, because the file system has
not been unmounted properly.

Of course, the system to be cloned should be as idle as
possible. Certainly I would not recommend to clone a machine with
active users on it or to use the cloned machine as a critical system.

- Felix
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