Linux disk layout

Red Hat Enterprise Linux 9.2 LPAR mode z/VM guest KVM guest

The Linux disk layout does not have a VTOC, and DASD partitions that are formatted with this layout cannot be accessed by traditional mainframe operating systems.

You can format only ECKD type DASD with the Linux disk layout. Apart from accessing the disks as ECKD devices, you can also access them using the DASD DIAG access method.

Figure 1 illustrates a disk with the Linux disk layout.

Figure 1. Linux disk layout
The graphic shows this order: first IPL record, second an optional volume label, LNX1, then one partition

DASDs with the Linux disk layout either have an LNX1 label or are not labeled. The first records of the device are reserved for IPL records and the volume label, and are not intended for use by Linux applications. All remaining records are grouped into a single partition. You cannot have more than a single partition on a DASD that is formatted in the Linux disk layout.

Linux can address the device as a whole as /dev/dasd<x>, where <x> can be one to four letters that identify the individual DASD. Linux can access the partition as /dev/dasd<x>1.

You use the dasdfmt command to format a disk with the Linux disk layout.