Creating Raw Partitions

Specific system administration is required before raw devices can be enabled and used. The available tools to configure devices depend on the distribution configuration.

Physical disk space must be allocated 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 IO:
1. 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)
```
2. Accept the default by pressing Enter when you see:
```
First cylinder (8013-8683, default 8013):
```
3. Accept the default by pressing Enter again, when you see:
```
Last cylinder or +size or +sizeM or +sizeK
(8013-8683, default 8683): 8269
```
4. Use the t command, enter “5” at this prompt:
```
Partition number (1-8):5
```
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)
```
6. Repeat the above steps to create four partitions for raw device IO.
7. 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.
The partition table can now be written to disk and you can quit the fdisk(8) utility.