-------- Original Message  --------
Subject: Re: [CentOS] Copy OS live to different hardware
From: Les Mikesell <lesmikesell@gmail.com>
To: CentOS mailing list <centos@centos.org>
Date: Monday, October 12, 2009 9:48:32 AM
Bob Puff wrote:
  
Hello,

I've got some CentOS 5.3 servers that I want to clone to a backup server,
possibly a VM machine.  I want this to be done while the server is up, and
keep it synced at least once a day.

I've done this already by using RSYNC, but here's the twist: the backup
machine could be different hardware, and needs to have a different IP address
(so they don't conflict).

My question: exactly what files should I exclude, so that I copy everything
-except- what pertains to the ethernet card(s), and hard drive mounts.  I know
of at least:

/etc/fstab
/etc/sysconfig/network-scripts/*
/var/run
/proc

But what else?  The original servers may have software raid, so those files
can't be copied either.
    

/dev, /sys and /boot - but it is a good idea to use rsync's 
--one-file-system option and explicitly copy the filesystems you want. 
Also, if you are changing files underneath running applications, expect 
some wierd things to happen.  It would be safer to plan to reboot the 
backup if you ever need to activate it - and if you do that you could 
have it running from a different root for the copies.

I think you'll have better luck if you virtualize the hardware on the production machine first. With virtualized hardware you don't need to worry so much about potential differences with RAID, NICs, etc - just shut down the existing instance of the VM and bring up the new one. Xen has a tool to do exactly what you are asking - clone a live VM. Most other VM technologies have a cloning feature, but only support cloning of a VM that has been shut down first.