[6] http://metalab.unc.edu/LDP/HOWTO/mini/Partition.html
“Primary” partitions are the original partitioning scheme for PC hard disks. However, there can be only four of them. To get past this limitation, “extended” or “logical” partitions were invented. By setting one of your primary partitions as an extended partition, you can subdivide all the space allocated to that partition into logical partitions. The number of logical partitions you can create is much less limited than the number of primary partitions you can create; however, you can have only one extended partition per drive.
Linux limits the number of partitions per drive to 15 partitions for SCSI drives (3 usable primary partitions, 12 logical partitions), and 63 partitions for IDE drives (3 usable primary partitions, 60 logical partitions).
The last issue you need to know about a PC BIOS is that your boot partition—that is, the partition containing your kernel image—needs to be contained within the first 1,024 cylinders of the drive. Because the root partition is usually your boot partition, you need to make sure your root partition fits into the first 1,024 cylinders.
If you have a large disk, you may have to use cylinder translation techniques, which you can set in your BIOS, such as LBA translation mode. (More information about large disks can be found in the Large Disk mini-HOWTO[[7]].) If you are using a cylinder translation scheme, your boot partition must fit within the translated representation of cylinder 1,024.
[7] http://metalab.unc.edu/LDP/HOWTO/mini/Large-Disk.html
2.3.4 Device Names in Linux
Linux disks and partition names may be different from those in other operating systems. You should know the names that Linux uses when you create and mount partitions. The basic scheme can be found in Table 2.1 on page [*].
Table 2.1: Linux Device Names
+------------------------------------------------------------------------------+
| Device | Linux Name |
|-----------------------------------------------+------------------------------|
| First floppy drive | /dev/fd0 |
|-----------------------------------------------+------------------------------|
| Second floppy drive | /dev/fd1 |
|-----------------------------------------------+------------------------------|
| First partition on /dev/hda (typically C: in | /dev/hda1 |
| other OSs) | |
|-----------------------------------------------+------------------------------|
| Fifth partition on /dev/hdc | /dev/hdc5 |
|-----------------------------------------------+------------------------------|
| Second partition on /dev/sdb | /dev/sdb2 |
|-----------------------------------------------+------------------------------|
| Entire Primary-Master IDE hard disk or CD-ROM | /dev/hda |
|-----------------------------------------------+------------------------------|
| Entire Primary-Slave IDE hard disk or CD-ROM | /dev/hdb |
|-----------------------------------------------+------------------------------|
| Entire Secondary-Master IDE hard disk or | /dev/hdc |
| CD-ROM | |
|-----------------------------------------------+------------------------------|
| Entire Secondary-Slave IDE hard disk or | /dev/hdd |
| CD-ROM | |
|-----------------------------------------------+------------------------------|
| First SCSI disk | /dev/sda |
|-----------------------------------------------+------------------------------|
| Second and remaining SCSI disks | /dev/sdb and so forth |
|-----------------------------------------------+------------------------------|
| First serial port (COM1 in other OSs) | /dev/ttyS0 |
|-----------------------------------------------+------------------------------|
| Second, third, etc. serial ports | /dev/ttyS1, /dev/ttyS2, etc. |
|-----------------------------------------------+------------------------------|
| SCSI tape units (automatic rewind) | /dev/st0, /dev/st1, etc. |
|-----------------------------------------------+------------------------------|
| SCSI tape units (no automatic rewind) | /dev/nst0, /dev/nst1, etc. |
|-----------------------------------------------+------------------------------|
| SCSI CD-ROMs | /dev/scd0, /dev/scd1, etc. |
+------------------------------------------------------------------------------+
The partitions on each disk are represented by appending a number to the disk name. For example, the names hda1 and hda2 represent the first and second partitions of the first IDE disk drive in your system. Linux represents the primary partitions with the drive name plus the numbers 1 through 4. For example, the first primary partition on the first IDE drive is /dev/hda1. The logical partitions are numbered starting at 5, so the first logical partition on that same drive is /dev/hda5. Remember that the extended partition—that is, the primary partition holding the logical partitions—is not usable by itself. This applies to SCSI drives as well as IDE drives.