The format of boot device names is:
[/interface/]dev@unit[,lun][:partition]
interface
SCSI interface type. One of: ‘spc@0', ‘spc@1', ‘mha@0'. If the dev is a SCSI device, and interface is omitted, the current boot interface is used.
dev
Device type. One of: ‘fd' (floppy disk drive), ‘sd' (SCSI disk), ‘cd' (SCSI CD-ROM), ‘md' (Memory disk).
unit
Device unit #. You must specify the target SCSI ID if dev is a SCSI device.
lun
SCSI LUN #. 0 is assumed if omitted.
partition
Partition letter of device. Partition ‘a' is used if omitted.