Migrating NetApp cloned LUNs for iSCSI boot

If you are booting a Linux system via iSCSI (using Broadcomm or Intel iSCSI-bootable Ethernet), certain information specific to your system is embedded in the Linux configuration during the OS installation. If you then clone that LUN and try to boot it with another system, all hell breaks loose. The system starts to boot and then “learns” during the boot process it’s old IP and MAC and iSCSI IQN information, which essentially makes it switch boot luns mid way through! Imagine the disaster that makes when you boot from LUN X and it starts to modify LUN Y!

Here are my quick notes on what it takes to “break” the relationships embedded on the boot/root LUN.

  • Install CentOS to HostA, booting from iSCSI NetApp LUN “lunA”
  • Create a lun clone “lunB”, and then do a non-space-efficient lun clone split in order to get rid of the snapshot dependencies between the systems.
  • Boot the HostA from the clone/copy “lunB”
  • Edit /boot/grub/grub.conf for new IP, new Ethernet MAC, new IQN. MAC addresses must be lowercase!
  • Edit¬†/etc/iscsi/initiatorname.iscsi
  • Edit /etc/sysconfig/network-scripts/ifconfig-eth* ¬†with the updated ethernet macs, IPs
  • Edit /ets/sysconfig/network for new hostname
  • Shutdown -h
  • boot the second host (HostB) from the modified copy (LunB) to test.

This is for a non-GUI system. If you are running a GUI and the second host doesn’t have the same video card, that will break and you will have to reconfigure X.

 

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