On Fri, Mar 04, 2011 at 10:31:18AM +0200, Jussi Hirvi wrote:

...

Is there any (easy?) way to migrate running standalone CentOS 4 or 5 systems to xen virtual stacks?

Rebuilding those systems from scratch on the xen machine would take plenty of work.

If you're talking about Xen PV domUs, then the process is pretty much like this:

• ssh into the standalone system.
• make sure /etc/modprobe.conf includes xenblk driver (so that it'll be

included in the generated initrd when you install kernel-xen).

• fix /etc/fstab to have xvd* (xen virtual disk) devices instead of sd*.
• install kernel-xen rpm.
• verify kernel-xen is the default in /boot/grub/grub.conf.
• verify root= parameter is correct in /boot/grub/grub.conf for

kernel-xen.

• copy/transfer all the files from the standalone system to virtual

disk/image.

Make sure here to copy with preserving hardlinks, use tar or rsync -aH for this. And, you can exclude some content like /dev/* (but not the directory /dev itself!).

• create a configuration file for the new domU, make it use pygrub

bootloader, and make it use xvd* disks/devices.

Also, you may have to adjust network config.

• done.

And, if something goes wrong, you can simply loop mount the filesystem on the Xen host and fix things, maybe chrooting before depending on what you do.

Simon

On Fri, Mar 4, 2011 at 4:57 AM, Simon Matter simon.matter@invoca.ch wrote:

...

...

On Fri, Mar 04, 2011 at 10:31:18AM +0200, Jussi Hirvi wrote:

...

Is there any (easy?) way to migrate running standalone CentOS 4 or 5 systems to xen virtual stacks?

Rebuilding those systems from scratch on the xen machine would take plenty of work.

If you're talking about Xen PV domUs, then the process is pretty much like this:

• ssh into the standalone system.
• make sure /etc/modprobe.conf includes xenblk driver (so that it'll be

included in the generated initrd when you install kernel-xen).

• fix /etc/fstab to have xvd* (xen virtual disk) devices instead of

sd*.

• install kernel-xen rpm.
• verify kernel-xen is the default in /boot/grub/grub.conf.
• verify root= parameter is correct in /boot/grub/grub.conf for

kernel-xen.

• copy/transfer all the files from the standalone system to virtual

disk/image.

Make sure here to copy with preserving hardlinks, use tar or rsync -aH for this. And, you can exclude some content like /dev/* (but not the directory /dev itself!).

Use "star". This will preserve SELinux configurations, which neither tar nor rsync do.

Ah, forgot about that, because I always disable SELinux - if I want it so secure I'd take OpenBSD :)

Simon

...

Make sure here to copy with preserving hardlinks, use tar or rsync -aH for this. And, you can exclude some content like /dev/* (but not the directory /dev itself!).

Use "star". This will preserve SELinux configurations, which neither tar nor rsync do.

The SELinux file contexts are stored in extended attributes, so you can use the --xattrs flag to rsync or tar to copy these across.

Kal

On 4.3.2011 11.42, Pasi Kärkkäinen wrote:

is pretty much like this:

• ssh into the standalone system.

Ok, thanks - that looks like a real how-to already. I will have to consider if I want to take the risk. With name server I would not bother, but with mail server maybe.

- Jussi