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Old 12-05-2005, 02:19 PM   #1
metrognome
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Registered: Dec 2005
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Migrating RHEL 3 to new (identical) chassis


Hello,

This is my first post here - please be gentle...

Just for a frame of reference I'm not a Linux noob but I'm not very deep into the nuts and bolts either.

We have a RHEL 3 server installed on a Dell PowerEdge. I have purchased new disks and have installed them in an identical chassis and done the raid config and all that. Now what I want to be able to do is find a way to transfer the existing filesystems, including /boot, to the new disks in the other chassis. When this is complete the old disks will be re-used in another rebuild.

I don't want to reinstall Linux on this new chassis as I want what I've got now on the other. I've had a consultant config and tweak it and I don't want call him in to do have to do that over again; I just want to move the whole server image over. I'll move the appropriate mount points onto the array once it's all moved over (there is a non-raided disk).

So what I need help with is choosing a bootable cd image that has the partitioning and copying tools I need. And I need to know what tools would be best to use for this kind of operation. Maybe I could even copy the filesystems to where I want them in one step but then I'd have to go into the fstab file wouldn't I?

Any suggestions on this would be greatly appreciated!

Thank you!

MetroGnome

Edit - for clarity.

Last edited by metrognome; 12-05-2005 at 02:20 PM.
 
Old 12-06-2005, 01:05 AM   #2
WhatsHisName
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Why not use rsync and transfer the system through a LAN connection.

Basically, on the receiving end, what works best is to have a small installation of something like FC4 (3GB desktop without office programs or even a minimal installation that includes rsync and possibly lvm2) to act as the “receiver”. You then assemble the new filesystems on a mount point and transfer over the other system.

On the sending end, you can make a similar small installation to act as the “transmitter”, analogous to what is described above. Alternatively, if you are using LVMs, then create logical volume snapshots, assemble them on a mountpoint and rsync them to the new system.

It's really easy to do.
 
Old 12-08-2005, 07:28 PM   #3
metrognome
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Thumbs up

Thanks for the suggestions Whatshisname! Maybe easy for you but this was uncharted territory for me. What I ended up doing was close but not quite what you suggested.

I'm going to describe my experience in the hopes that someone else can benefit from it.

The scenario is that I needed to find an easy way to transfer a server to new disks. I wanted to do it without taking the time to actually install a temporary OS on the target disks and restoring from tape. We have a nearly (except for processor speed) identical chassis so, in theory, it should be possible to transfer to the new disks in the second chassis and when complete, just move the new disks to the old chassis.

As I mentioned I'm not a Linux or a server newbie but -- I'm not a Linux server admin. At this point I think I'm dreaming but it's worth a try.

The chassis are Dell PowerEdge 2650s. They are dual Xeon machines with 2GB of RAM and Perc 3/Di raid controllers. I consulted Dell and, in this case, it's the raid controllers that are paramount. They must be the same model and the same firmware revision to move the disks from one chassis to another successfully.

Let's call the existing server chassis C1 and the second chassis C2.

I installed the new disks in C2, booted into the raid controller's firmware, and configured the disks and the array containers. Once the containers were scrubbed I booted the chassis with a Knoppix bootable CD. I used gparted to partition the new drives. I could have mounted them by hand but it was easier to just reboot that Knoppix CD which auto-detects drive partitions and mounts them in read-only mode.

I shut down the RHEL 3 server on C1 and booted it with a Knoppix CD as well. I had researched rsync and rsyncd.conf by this point so I created an rsyncd.conf file in the Knoppix instance of /etc (not the server's /etc). It took a couple of tries to get this file right but once I did I had a read-only "module" for each of my server's mountpoints. I ran "rsync --daemon" once I got the conf file right.

On C2 I remounted the new filesystems in read-write mode and ran the rsync command against the daemon on C1. This is where the perfecting of the rsyncd.conf on C1 comes in so there were a few cycles of this while I got that file right. Once I did it took surprisingly little time to transfer all of the filesystems from C1 to C2.

I rebooted C2 with the RHEL 3 boot disk and typed "linux rescue" at the prompt. I let it continue and it was able to autodetect the newly transferred root partition and mounted it as /mnt/sysimage. I then edited the /mnt/sysimage/etc/fstab to reflect the new partition locations.

The only issue now is the bootloader. The RHEL 4 System Admin guide is what came up in my Googling and the instructions work great for RHEL 3 as well. Still in "rescue" mode I chrooted /mnt/sysimage and then ran "/sbin/grub-install /dev/sda".

I rebooted the system and, much to my shock, it worked. It complained that the network cards had unexpectedly changed mac addresses but it's in the wrong chassis so I'm not surprised. I was then able to transfer the new drives from C2 into C1 and reboot. Just tell the raid controller to accept the drive configuration and it boots great. Old server running on new drives.

Maybe this is regular stuff for some out there but it was new territory for me so I'm very happy and a little surprised at how well it went.

Hope this helps someone else.

Here are some of the links I used to research what I needed to do:

(Hmmm. It won't let me post the URLs so I dunno what to do about that one.)

Thanks again!

MetroGnome
 
  


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