Release Notes

Linux setup and configuration
29 Dell EMC PowerVault ME4 Series and Linux | 3924-BP-L
4. Change the snapshot volume’s UUID. This step is not necessary if step 2 has been executed.
a. Use the uuidgen command to generate a new unique UUID on the host.
b. For xfs, use the xfs_admin -U command to change the filesystem UUID to the new UUID.
# uuidgen
09d56888-eb9f-4a8d-9e9e-bca028edf4ef
# xfs_admin -U 09d56888-eb9f-4a8d-9e9e-bca028edf4ef /dev/mapper/mpathe
Clearing log and setting UUID
writing all SBs
new UUID = 09d56888-eb9f-4a8d-9e9e-bca028edf4ef
c. For ext4, RHEL 7.5 allows mounting the filesystem even though it has a duplicate UUID. It is
recommended to change the UUID regardless to avoid future confusion and conflicts.
Use the uuidgen and tune2fs -U command to change the filesystem UUID to the new UUID.
# uuidgen
6028cf0d-9a0a-4150-99ab-3ff35c6fd550
# tune2fs /dev/mapper/mpathg -U 6028cf0d-9a0a-4150-99ab-3ff35c6fd550
tune2fs 1.42.9 (28-Dec-2013)
# blkid /dev/mapper/mpathg
/dev/mapper/mpathg: UUID="6028cf0d-9a0a-4150-99ab-3ff35c6fd550"
TYPE="ext4"
5. Mount the file system using the normal process.
Note: Without changing the UUIDs, the snapshot volume group and file system cannot be mounted on the
same system.
3.6.2 Using snapshots to roll back or reset a volume
The rollback feature replaces the data of a source volume/snapshot with the data of another snapshot that is
created from it. This is useful to quickly restore a point-in-time copy of data on the original host without
reconfiguring the applications on the host.
The reset feature replaces the data of a snapshot with the current data of the source volume. A common use
case would be to resynchronize the test data with the most up-to-date data from the production source
volume.
Since the rollback and reset features preserve the mapping and identity of the volume, there is no
reconfiguration needed on the host. Although I/O access to the volume is restricted while the rollback or reset
is in progress, it is highly recommended to dismount the volume on the host and restrict user access to the
data. For filesystem, use the umount command to dismount. For LVM, use the vgchange -a n command to
disable the volume group. If the volumes are controlled by applications, such as Oracle ASM, stop the
applications using application-provided utilities. Once the process is complete, reactive LVM, file systems,
and applications.