Creating a DD image from z/VM disk

Create a disk image from the multipath device using the dd command.

Before you begin

Ensure that you have:

The FCP disk attached and available as a multipath device on the management server
Sufficient storage space for the DD image (at least the size of the source disk)
Root access on the management server

About this task

This phase creates a raw disk image from the z/VM disk that can be converted to QCOW2 format for use in OpenShift Virtualization.

Procedure

Identify the multipath device by running the following command:
```
multipath -ll
```

Check device information by running the following commands:

lsblk /dev/mapper/mpathb
fdisk -l /dev/mapper/mpathb

Example output:

Disk /dev/mapper/mpathb: 50 GiB, 53687091200 bytes, 104857600 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x647dac19

Device              Boot   Start      End  Sectors  Size Id Type
/dev/mapper/mpathb1         2048  9766911  9764864  4.7G 83 Linux
/dev/mapper/mpathb2      9766912 97656831 87889920 41.9G 83 Linux

Create the DD image.
Use the dd command to create a raw disk image:
```
dd if=/dev/mapper/mpathb of=image_name.img bs=4M status=progress conv=sync,noerror
```
Parameters:
- if: Input file (source multipath device)
- of: Output file (destination image file)
- bs: Block size (optional, improves performance)
- status=progress: Display progress information
- conv=sync,noerror: Optional error handling (do not stop on errors, fill with zeros)
Tip: The bs=4M parameter improves performance by using larger block sizes. The conv=sync,noerror parameter ensures the operation continues even if read errors occur, filling bad sectors with zeros.

Results

A raw disk image file is created that contains a complete copy of the z/VM disk, including all partitions and data.