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I have an existing Centos 5 installation. I would like to upgrade to Ubuntu. Thing is, I don't want to be down for as long as it will take to get my entire environment moved over - software installed, connectivity configured, etc. I'd like to take it one step at a time.

But I don't really want to keep rebooting back and forth from the new OS to the old OS. That's what I did last time I upgraded to a new OS, and it got old real fast.

So, since my new MB is virtualization-ready (AMD Phenom II 945 quad-core), I figured I could create a virtual machine, under the new OS installation, that ran the old OS installation.

The problem is that the documentation I've been able to find has been pretty sparse. I've found a lot of possibilities, and little info on which would be capable of doing what I want.

I have a new Ubuntu 9.10 installation, and a second disk containing the Centos 5 installation. And I don't know where to go next.

Any help would be appreciated.

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migrated from stackoverflow.com Feb 21 '10 at 0:52

This question came from our site for professional and enthusiast programmers.

2  
Should this be on ServerFault.com? –  Mark Allen Feb 21 '10 at 0:25
    
are you sure about that ubuntu version number? It doesn't look right –  nbv4 Feb 21 '10 at 0:25
    
Sorry, Ubunto 9.10 –  Jeff Dege Feb 21 '10 at 0:38
    
This is content for superuser.com –  er4z0r Feb 21 '10 at 0:39
    
@Mark This is a good question. If your avatar wasn't a bulldog I would definitely have something to add. –  Pascal Cuoq Feb 21 '10 at 0:39

3 Answers 3

Setting up a virtual environment is possible, but may not be what you need. If you really want it, look into VMware's converter to read the Centos disk and create a VM, then use VMPlayer to run that VM under Ubuntu. I've found these tools to be pretty easy to use.

VMware converter will read the disk and create a new disk image file - this means you need to have a place big enough to put this disk image. However, I believe it is also possible to create a VM that uses the physical disk image, I just haven't used VMPlayer this way myself.

Since you say you have these on separate disks, I'm assuming you mean you have two harddrives, one with Ubuntu and one with Centos. Why not just make sure both disks are plugged in and running?

With Ubuntu running as the boot disk, create a mount point mkdir /centos, mount the disk there with something like mount /dev/sdb1 /centos and look for any info you need on the Centos disk. To make that permanent, add a line to /etc/fstab something like

/dev/sdb1 /centos ext3 defaults 1 2

Most of the system info you want will be under /centos/etc, and you should be able to use your existing Centos disk /centos/home/ as your login directory, so you don't even need to copy your home directory to the new disk.

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If you feel confident, you can try VirtualBox with raw disk support. This should leave your system on a separate partition/drive intact. However, I'm not sure how your system would react to switching back and forth between virtualized and normal boot. Windows could probably freak out here. ;-)

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KVM is really good for non-graphical VM's. VMWare is a pain these days in Linux IMHO. I've switched to VirtualBox and have been happy running various VM's (including Windows 7) on Ubuntu AMD64 9.10 and 9.04 installs.

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