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39 Dell EMC SC Series: Red Hat Enterprise Linux Best Practices | CML1031
aliases within /etc/multipath/bindings and /etc/multipath/wwids are also automatically updated to reflect
any boot device changes.
Note: Ensure that the original boot-from-SAN volume is no longer mapped to the server object and the
snapshot view volume is mapped to the Linux system as LUN ID 0.
If the OS fails to boot, the reason might be that old sdX devices or old WWIDs are still being referenced.
Therefore, additional steps must be taken to allow the snapshot view volume to boot. The following procedure
demonstrates a method to examine and modify the configuration files on the snapshot view volume on a
RHEL 6 system.
1. Create a snapshot view volume from the boot-from-SAN snapshot.
2. Map the snapshot view volume to another Linux system that is able to interpret and mount the base
file system type.
3. Mount the /boot and /devices of this snapshot view volume (/dev/sdc in this case).
# mkdir /mnt/snapshot-boot
# mkdir /mnt/snapshot-root
# mount /dev/sdc1 /mnt/snapshot-boot
# mount /dev/sdc3 /mnt/snapshot-root
4. Determine the WWID of the snapshot view volume. See section 3.1 for details.
5. Update the /etc/multipath.conf file to use the new WWID value.
# vi /mnt/snapshot-root/etc/multipath.conf
6. Review and update the /mnt/snapshot-root/etc/fstab file if necessary.
7. Review and update the /boot/grub/grub.conf if necessary
8. Map the volume to the original system as LUN ID 0 and boot the system.
Note: The system boot might fail with the invalid multipath tables error because of the obsolete WWNs.
Continue performing these steps to remove/update them.
9. Mount the OS ISO and boot into rescue mode.
10. Mount the boot-from-SAN volume.
# chroot /mnt/sysimage
11. Resolve the multipath error by commenting out the old entries and adding new entries in the bindings
and wwids files.
# vi /mnt/sysimage/etc/multipath/bindings
# vi /mnt/sysimage/etc/multpath/wwids
12. Create a new initramfs file. Substitute $kernel-release with the correct version of your system.
# /mnt/sysimage/sbin/dracut -v /mnt/sysimage/boot/<initramfs-$kernel-
release.img>
13. Update /mnt/sysimage/boot/grub/grub.conf to use the new initrd/initramfs file. Optionally, create
a new entry and retain the old entry for a recovery option.
14. Reboot the system using the new initrd/initramfs file. Verify that the dm-multipath is working as
normal.