Specific
system administration is required before you can enable and use raw devices. The available tools to configure devices depend on the distribution configuration.
You must allocate physical disk space in partitions on the
disks where you want to set up raw devices. The physical IO subsystem
can be on either SCSI or EIDE devices.
Note: You can create partitions with the Linux default fdisk(8) utility.
You must have "root" privileges to use the command fdisk.
See the fdisk(8) man pages for a complete description
of the command.
Example 1
This example shows how to set up partitions as raw devices,
on four SCSI disks in the system—
sda,
sdb,
sdc,
and
sdd.
- Start fdisk on /dev/sdd:
# fdisk /dev/sdd
The system returns:
The number of cylinders for this disk is set to 8683
....
Command (m for help):
- Enter p to print the current
partition layout. The output is:
Disk /dev/sdd: 64 heads, 32 sectors, 8683 cylinders
Units = cylinders of 2048 * 512 bytes
Device Boot Start End Blocks Id System
/dev/sdd1 1 7499 7678960 83 Linux
/dev/sdd2 7500 8012 525312 82 Linux swap
/dev/sdd4 8013 8683 687104 5 Extended
Example 2
This example shows the extended partition (
sdd4)
has 687104 free blocks, starting from 8013 and ending at 8683. You
can assign the remaining partitions later. This example assigns an additional partition for raw bound
disk I/O:
- Use the n command
to create a new partition, and enter l at this
prompt for "logical":
Command (m for help): n
Command action
l logical (5 or over)
p primary partition (1-4)
- Accept the default by pressing Enter when you see:
First cylinder (8013-8683, default 8013):
- Accept the default by pressing Enter again, when
you see:
Last cylinder or +size or +sizeM or +sizeK
(8013-8683, default 8683): 8269
- Use the t command, enter 5 at
this prompt:
Partition number (1-8): 5
- Enter 60 at this prompt:
Hex code (type L to list codes): 60
The output is:
Changed system type of partition 5 to 60 (Unknown)
- Repeat steps 1–5 to create four partitions
for raw device I/O.
- Verify the setup using p to print the full
partition table before writing it out. Make sure that there are
no overlapping partitions and the type for the unassigned partitions
is Unknown type 60.
You can now write this partition table to disk and quit the
fdisk(8) utility.