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Community ▶ Questions ▶ Gotchas when upgrading from Xen to KVM?
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Gotchas when upgrading from Xen to KVM?

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I've been dragging my feet for quite some time on upgrading my Linode from Xen to KVM because of worries about something breaking when I try.

So I'm wondering what if any issues/gotchas those of you who have upgraded from Xen to KVM have seen?

If it matters, I'm running a 32-bit Ubuntu 14.04 with the latest Linode-provided 32-bit kernel (I've been on Linode for at least 5 years and there was a good reason at the time why I went 32-bit back then and I haven't had the time to set up a new 64-bit Linode and copy the data over and just run 64-bit).

Admittedly, I'm also thinking that rather than do this upgrade perhaps now is the time to bite the bullet, spin up a new 64-bit Linode, and transfer over.

3 Replies

I think you just need to go to the 64 bit kernel to migrate, then once you have migrated , you can change back to the 32 bit kernel. You don't need to worry about your applications, they can stay at 32 bit.

I'm using the latest Linode supplied 32 bit kernel on KVM.

So you didn't have any problems? How did things worth with the block device naming scheme change? Right now my /etc/fstab has references to /dev/xvda and so on. But Linode says under KVM they are named /dev/sda and so on? Does the migration process detect and change these? Will the machine even boot after the migration or will I need to boot it off one of the available rescue kernels so I can modify /etc/fstab and then go back to the normal kernel?

I was running the Debian distribution kernel before I switched, and I don't remember the device names in play at the time.

I think I switched back to the linode 64 bit kernel and then upgraded. Once I upgraded I found I could select the 32 bit kernel again.

I think I looked at a few posts on the forums here and the maybe a proceedure in linode docs. It was a while ago, so I'm not 100% sure, but I don't remember any "Oh crap" moments.

I was aprehansive as well. A quick search of the forums found these:

https://forum.linode.com/viewtopic.php?f=27&t=11910&hilit=switch+to+KVM

https://forum.linode.com/viewtopic.php?f=27&t=11852&hilit=switch+to+KVM

For filesystem helpers in the control panel, I have everything set to yes except networking, as I'm running static network configs. I think this takes care of the fstab stuff.

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