You can recover a management domain from a snapshot-based backup when severe disaster conditions damage the management domain, or when the server hardware is replaced to such an extent that it amounts to new hardware.

1. Prepare an NFS server to host the backup archive mybackup.tar.bz2.

   The NFS server must be accessible by IP address. For example, on an NFS server with the IP address nfs_ip, where the directory /export is exported from NFS mounts, put the mybackup.tar.bz2 file in the /export directory

2. Restart the recovery target system using the diagnostics.iso file.
   See Booting a Server using the Diagnostic ISO File in Oracle Exadata System Software User's Guide.
3. Log in to the diagnostics shell as the root user.
   When prompted, enter the diagnostics shell.

   For example:

   Choose from following by typing letter in '()':
   (e)nter interactive diagnostics shell. Must use credentials 
   from Oracle support to login (reboot or power cycle to exit
   the shell),
   (r)estore system from NFS backup archive, 
   Type e to enter the diagnostics shell and log in as the root user.

   If prompted, log in to the system as the root user. If you are prompted for the root user password and do not have it, then contact Oracle Support Services.
4. If required, use /opt/MegaRAID/storcli/storcli64 (or /opt/MegaRAID/MegaCli/MegaCli64 for releases earlier than Oracle Exadata System Software 19c) to configure the disk controller to set up the disks.
5. Remove the logical volumes, the volume group, and the physical volume, in case they still exist after the disaster.

   # lvm vgremove VGExaDb --force
   # lvm pvremove /dev/sda2 --force

6. Remove the existing partitions and clean up the drive.

   # parted
   GNU Parted 2.1
   Using /dev/sda
   Welcome to GNU Parted! Type 'help' to view a list of commands.
   (parted) rm 1 
   [12064.253824] sda: sda2
   (parted) rm 2 
   [12070.579094] sda: 
   (parted) q
   
   # dd if=/dev/zero of=/dev/sda bs=64M count=2

7. Create the two partitions on /dev/sda.
   1. Get the end sector for the disk /dev/sda from a running dom0 and store it in a variable:

      # end_sector_logical=$(parted -s /dev/sda unit s print|perl -ne '/^Disk\s+\S+:\s+(\d+)s/ and print $1')
      # end_sector=$( expr $end_sector_logical - 34 )
      

      The values for the start and end sectors in the commands below were taken from an existing management domain. Because these values can change over time, it is recommended that these values are checked from an existing management domain using the following command:

      # parted -s /dev/sda unit S print

   2. Create the boot partition, /dev/sda1.

      # parted -s /dev/sda mklabel gpt mkpart primary 64s 1048639s set 1 boot on

   3. Create the partition that will hold the LVMs, /dev/sda2.

      # parted -s /dev/sda mkpart primary 1048640s 3509759966s set 2 lvm on

8. Use the /sbin/lvm command to re-create the logical volumes and mkfs to create file systems.
   1. Create the physical volume and the volume group.

      # lvm pvcreate /dev/sda2
      # lvm vgcreate VGExaDb /dev/sda2
      

   2. Create the logical volume for the file system that will contain the / (root) directory and label it.

      # lvm lvcreate -n LVDbSys3 -L30G VGExaDb
      # mkfs -t ext4 –b 4096 /dev/VGExaDb/LVDbSys3
      # e2label /dev/VGExaDb/LVDbSys3 DBSYSOVS
      

   3. Create the logical volume for the swap directory, and label it.

      # lvm lvcreate -n LVDbSwap1 -L24G VGExaDb
      # mkswap -L SWAP /dev/VGExaDb/LVDbSwap1
      

   4. Create the logical volume for the backup partition, and build a file system on top of it.

      # lvm lvcreate -n LVDbSys2 -L30G VGExaDb
      # mkfs -t ext4 –b 4096 /dev/VGExaDb/LVDbSys2

   5. Create the logical volume for the reserved partition.

      # lvm lvcreate -n LVDoNotRemoveOrUse –L1G VGExaDb

      Note:

      Do not create any file system on this logical volume.
   6. Create the logical volume for the guest storage repository.

      # lvm lvcreate -l 100%FREE -n LVDbExaVMImages VGExaDb
      

   7. Create a file system on the /dev/sda1 partition, and label it.

      In the mkfs.ext3 command below, the -I 128 option is needed to set the inode size to 128.

      # mkfs.ext3 -I 128 /dev/sda1
      # tune2fs -c 0 -i 0 /dev/sda1
      # e2label /dev/sda1 BOOT
      

9. Create mount points for all the partitions, and mount the respective partitions.

   For example, if /mnt is used as the top-level directory, the mounted list of partitions might look like:

   • /dev/VGExaDb/LVDbSys3 on /mnt

   • /dev/sda1 on /mnt/boot

   The following example mounts the root file system, and creates two mount points:

   # mount /dev/VGExaDb/LVDbSys3 /mnt -t ext4
   # mkdir /mnt/boot
   # mount /dev/sda1 /mnt/boot -t ext3
   

10. Bring up the network on eth0 and assign the host's IP address and netmask to it.

    # ifconfig eth0 ip_address_for_eth0 netmask netmask_for_eth0 up
    # route add -net 0.0.0.0 netmask 0.0.0.0 gw gateway_ip_address
    

11. Mount the NFS server holding the backups.

    # mkdir -p /root/mnt
    # mount -t nfs -o ro,intr,soft,proto=tcp,nolock nfs_ip:/location_of_backup /root/mnt
    

12. From the backup which was created in Backing up the Management Domain dom0 Using Snapshot-Based Backup, restore the root directory (/) and the boot file system.

    # tar -pjxvf /root/mnt/backup-of-root-and-boot.tar -C /mnt

13. Unmount the restored /dev/sda1 partition, and remount it on /boot.

    # umount /mnt/boot
    # mkdir -p /boot
    # mount /dev/sda1 /boot -t ext3
    

14. Set up the grub boot loader using the command below:

    # grub --device-map=/boot/grub/device.map << DOM0_GRUB_INSTALL
    root (hd0,0)
    setup (hd0)
    quit
    DOM0_GRUB_INSTALL
    

15. Unmount the /boot partition.

    # umount /boot

16. Detach the diagnostics.iso file.

    Using the ILOM Web interface, navigate to the Storage Devices dialog and click Disconnect.

    The Storage Devices dialog is the interface that you earlier used to attach the diagnostics.iso image. See Booting a Server using the Diagnostic ISO File in Oracle Exadata System Software User's Guide.

17. Check the restored /etc/fstab file and comment out any reference to /EXAVMIMAGES.

    # cd /mnt/etc

    Comment out any line that references /EXAVMIMAGES.

18. Restart the system.

    # shutdown -r now

    This completes the restoration procedure for the management domain (dom0).

19. Convert to Eighth Rack, if required.

    If the recovery is on an Oracle Exadata Eighth Rack, then perform the procedure described in Configuring Oracle Exadata Database Machine Eighth Rack Oracle Linux Database Server After Recovery".

20. When the server comes back up, build an OCFS2 file system on the LVDbExaVMImages logical volume.

    # mkfs -t ocfs2 -L ocfs2 -T vmstore --fs-features=local /dev/VGExaDb/LVDbExaVMImages --force

21. Mount the OCFS2 partition on /EXAVMIMAGES.

    # mount -t ocfs2 /dev/VGExaDb/LVDbExaVMImages /EXAVMIMAGES

22. In /etc/fstab, uncomment the references to /EXAVMIMAGES and /dev/mapper/VGExaDb-LVDbExaVMImages, which you commented out earlier.
23. Mount the backup NFS server that holds the storage repository (/EXAVMIMAGES) backup to restore the /EXAVMIMAGES file system.

    # mkdir -p /root/mnt
    # mount -t nfs -o ro,intr,soft,proto=tcp,nolock nfs_ip:/location_of_backup /root/mnt
    

24. Restore the /EXAVMIMAGES file system.

    To restore all user domains, use this command:

    # tar -Spxvf /root/mnt/backup-of-exavmimages.tar -C /EXAVMIMAGES

    To restore a single user domain from the backup, use the following command instead:

    # tar -Spxvf /root/mnt/backup-of-exavmimages.tar -C /EXAVMIMAGES EXAVMIMAGES/<user-domain-name-to-be-restored>

25. Bring up each user domain.

    # xm create /EXAVMIMAGES/GuestImages/user_domain_hostname/vm.cfg