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Techtips Vol1 – Xen on CentOS – Migrating a Legacy Server | Russ Greenwald

Techtips Vol1 – Xen on CentOS – Migrating a Legacy Server

Xen on Centos – Migrating a legacy server

Do you have a legacy server, running legacy software, still used by your company or worse a client?  Are the developers and engineers who set it up long gone, do you have documentation on the design, anything?  No worries… I recently ran into this situation and I’ve found a very nice solution. I have a client who was running a client facing software package on a Fedora Core 3 server.  The power supply had recently died, fortunately we had a spare, the hardware was over 5 years old, and it was not RAID.  We were backing up what we could, but had little confidence on rebuilding it perfect if we had to.

I found using XEN via Centos 5 solved our immediate concerns, and bought us an infinite amount of time to plan for a more permanent solution.

Situation

  1. We have legacy software running on legacy hardware.  OS was Fedora Core 3, which we can agree is legacy, and hardware was home customization.

  2. We have a Dell server running Centos 5, which RAID 5, multi core’s, etc.  64 bit OS.

Process

  1. Downloaded http://et.redhat.com/~rjones/tmp/virt-p2v-0.9.9.iso and burned it to a CD
  • You will need to know the IP of the newer server
  • The newer server will need to allow SSH
  • Note the MAC address of the legacy server’s NIC
  1. Boot the legacy hardware off the CD
  • For network configuration choose automatic
  • When it comes to the device screen, the default is typically your primary HD.  Confirm and hit ok. If not select your primary /dev/sd device
  • The next screen should be your primary root directory. Confirm or change and hit ok.
  • Choose XEN for the hypervisor
  • When prompted for the MAC address of your new image, enter your legacy server’s MAC address (if this matters to you, i.e. reserved dhcp addresses)
  • Now wait as the p2v software scp’s your legacy hardware to a virtual image on your new server.
  • It will copy the image to /var/lib/xen/images/ on your new server.  It will create two files, a .conf file and a .img file
  1. On your newer CentOS5 server (after the copy is finished)
  • Yum install kernel-xen xen xen-libs virt-manager
  • edit /etc/grub.conf so the server boots off the xen kernel
  • Make sure the BIOS of the server has virtualization enabled on the processor
  • Reboot
  • After reboot go into /var/lib/xen/images and type virsh define p2v-foo-2008MMDDHHMM.conf, where p2v-foo etc is your new conf file.
  • Go into /etc/xen and edit foo
  1. Where you see the MAC address add an entry for bridging ethernet i.e. [ “mac=00:02:B3:5D:E6:CF,bridge=xenbr0” ]
  2. If your new OS is 64 bit and you installed 64 bit XEN change the line device_model = “/usr/lib64/xen/bin/qemu-dm” to reflect lib64 instead of just lib.
  • Now type virsh start foo
  • You can use virt-manager to see if the new Xen-VM booted properly and get to its console.
  • To have the new Virtual Server start on Hardware reboot move the /etc/xen/foo file into /etc/xen/auto/.

references: http://et.redhat.com/~rjones/virt-p2v/ Google XM commands, Virsh Commands, Xen Centos for more.


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