[Udpcast] Cloning Live Machine

Felix Rauch rauch at inf.ethz.ch
Wed Jul 21 00:57:43 CEST 2004


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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