Comments on: Minimizing Downtime on a Linux Migration

Question: Minimizing Downtime on a Linux Migration

Anonymous — Thu, 30 Mar 2006 23:37:09 -0800

I need help migrating to Linux from an "unlicensed" Windows 2000 Server?

I have inherited a problem at work. We host web/email for roughly 10 domains on a Windows 2000 server box that I have discovered is not properly licensed.

Since I have no budget to license any of the software currently running on the server, and I have have a good amount of experience running Debian hosting boxes I would like to migrate.

The key here is that I need to minimize downtime. How do I do this? I have no access to a backup or a temporary server. I will somehow have to install Debian and all of the standard Internet hosting services (apache, mysql, courier, bind, etc.) without skipping a beat.

Is there a way to setup the debian configuration on a virtual machine on my workstation and install the image onto the server hard disk?

Any idea? Suggestions? Tutorials? All are welcome. Thanks.

By: ori

ori — Fri, 31 Mar 2006 00:07:44 -0800

What's your website like? Static HTML pages or mySQL / PHP / Rails wizardy? That makes a big difference.

By: devilsbrigade

devilsbrigade — Fri, 31 Mar 2006 01:09:45 -0800

Yeah, you want to make a disk image and just mirror that right over. Make sure you have proper hardware drivers for all your components in the new machine.

One thing to remember with disk images is that your drive configuration has to be identical. If fstab (or worse, lilo or grub) on your image says your usr (or root!) partition is /dev/hda2, and on the new machine its /dev/hde2 (on a different controller, for instance) you be fucked.

By: slater

slater — Fri, 31 Mar 2006 01:10:24 -0800

"I will somehow have to install Debian and all of the standard Internet hosting services (apache, mysql, courier, bind, etc.) without skipping a beat."

You *could* do that by doing the installing on a different HD, then just swapping the startup HDs round? Either way you're going to have downtime, but this should get you closer to that "without skipping a beat" thing.

Also, isn't this all a bit "Murphy's law"? Sounds like an admin's worst nightmare... :-/

By: voidcontext

voidcontext — Fri, 31 Mar 2006 06:30:24 -0800

You could set the new server up on an external drive. Can your server boot from an external hard drive?

Once you've verified everything is working by running off the external drive, you can then set up the server's internal drive based on the external drive.

This way you're not wiping out the current server config until you're ready to go, and at all times you have a working server able to boot.

Make sure to have backups of course.

By: delmoi

delmoi — Fri, 31 Mar 2006 08:15:21 -0800

How much traffic do you get? Just buy an old junker PC, and use that as a 'testing server' to get everything setup on.

Then, once everything works on the test server, copy the entire filesystem (except for the OS) On Linux this would mean copying the /etc, /usr, and /bin folder plus anything else you've changed.

I know on freeBSD there is actually a way to figure out what files have been modified from the base install. There should be a way to do this on Linux as well.

So the quickest way to do this would be

1) Setup and configure standin server
2) generate a 'patch' based on changes you made to the machine from the base install
3) point domains to standin server
4) install Debian base on server
5) install patch
6) point domains back to the new machine.

By: anildash

anildash — Sat, 01 Apr 2006 01:58:41 -0800

virtualization might let you move individual services one at a time.