Technical data

SunOS 5.5 Devices cmdk(7D)
NAME cmdk − common disk driver
AVAILABILITY x86
DESCRIPTION The cmdk device driver is a common interface to various disk devices. The driver sup-
ports magnetic fixed disks, magnetic removable disks, and both 512-byte and 2K-byte
CD-ROM drives.
The block-files access the disk using the system’s normal buffering mechanism and are
read and written without regard to physical disk records. There is also a "raw" interface
that provides for direct transmission between the disk and the user’s read or write buffer.
A single read or write call usually results in one I/O operation; raw I/O is therefore con-
siderably more efficient when many bytes are transmitted. The names of the block files
are found in /dev/dsk; the names of the raw files are found in /dev/rdsk.
I/O requests to the magnetic disk must have an offset and transfer length that is a multi-
ple of 512 bytes or the driver returns anEINVAL error. However, I/O requests to the
2K-byte CD-ROM drive must be a multiple of 2K bytes. Otherwise, the driver returns an
EINVAL error, too.
Slice 0 is normally used for the root file system on a disk, slice 1 as a paging area (for
example, swap), and slice 2 for backing up the entire Solaris fdisk partition. Other slices
may be used for usr file systems or system reserved area.
Fdisk partition 0 is to access the entire disk and is generally used by the fdisk(1M)
program.
FILES /dev/dsk/cntndn[s|p]n block device (SCSI)
/dev/dsk/cndn[s|p]n block device (IDE)
/dev/rdsk/cntndn[s|p]n raw device (SCSI)
/dev/rdsk/cndn[s|p]n raw device (IDE)
where:
cn controller n
tn target id n (0-6)
dn lun n (0-7)
sn UNIX system slice n (0-15)
pn fdisk partition (0)
SEE ALSO fdisk(1M), mount(1M), lseek(2), read(2), write(2), directory(3C), vfstab(4), dkio(7I)
modified 20 Jul 1994 7D-67