Backing up a Linux volume with partitions

z/OS® treats a Linux partition (such as /dev/dasd/0198/part1) as a data set. The data set is named LINUX.Vvolser.PART000x.NATIVE for a data partition, or LINUX.Vvolser.PART000x.SWAP for a swap partition.

Here, volser is the volume serial number assigned to the volume when dasdfmt formatted the volume. fdasd can change the volser, too. The volser must be unique for z/OS to process it.

The x in PART000x is most likely the partition number, minus one. For example, a Linux partition such as /dev/dasd/0198/part2 would be known to z/OS as the data set LINUX.VLNX200.PART0001.NATIVE, where LNX200 is the volser of the volume.

Attention: If a partition is mounted read/write while undergoing a dump operation, data written to the partition during the dump operation might not be included in the backup. Because Linux uses deferred writes, unmounting a partition or remounting a partition read-only also serves to flush Linux's internal memory buffers to disk. Instead, process the dump when Linux is down, or when the partitions currently being backed up are unmounted or mounted read-only. If the partitions are mounted read/write, DFSMSdss can back up your data, but the data might be inconsistent. By unmounting or remounting a partition read-only, you can help to ensure that all of your data is backed up. You are not required to do this, but it provides the best copy. Below is an example of mounting a partition read-only:

mount -t ext2 -r /dev/dasd/019b/part1 /mntpoint

The data sets and the partitions they represent use this naming convention:

Data Set Names                        Partition Names
LINUX.Vvolser.PART0000.type          /dev/dasd/yyyy/part1
LINUX.Vvolser.PART0001.type          /dev/dasd/yyyy/part2
LINUX.Vvolser.PART0002.type          /dev/dasd/yyyy/part3

where:

volser is the volume serial number of the volume where the data set resides.
yyyy is the device number of the volume in the Linux environment.
type can be NATIVE or SWAP. You might decide that you need to back up only certain NATIVE partitions. SWAP partitions are the Linux equivalent to z/OS page packs.

Do not rename the data sets. fdasd expects the 24th character to be an 'N' or an 'S'. Otherwise, fdasd cannot recognize the partition type.