# Device Names in Linux

Linux disks and partition names may be different from other operating systems. You need to know the names that Linux uses when you create and mount partitions. Here's the basic naming scheme:

- The first hard disk detected is named `/dev/sda`.

- The second hard disk detected is named `/dev/sdb`, and so on.

- The first SCSI CD-ROM is named `/dev/scd0`, also known as `/dev/sr0`.

- The first DASD device is named `/dev/dasda`.

- The second DASD device is named `/dev/dasdb`, and so on.

The partitions on each disk are represented by appending a decimal number to the disk name: `sda1` and `sda2` represent the first and second partitions of the first SCSI disk drive in your system.

Here is a real-life example. Let's assume you have a system with 2 SCSI disks, one at SCSI address 2 and the other at SCSI address 4. The first disk (at address 2) is then named `sda`, and the second `sdb`. If the `sda` drive has 3 partitions on it, these will be named `sda1`, `sda2`, and `sda3`. The same applies to the `sdb` disk and its partitions.

Note that if you have two SCSI host bus adapters (i.e., controllers), the order of the drives can get confusing. The best solution in this case is to watch the boot messages, assuming you know the drive models and/or capacities.

Linux represents the primary partitions as the drive name, plus the numbers 1 through 4. For example, the first primary partition on the first drive is `/dev/sda1`. The logical partitions are numbered starting at 5, so the first logical partition on that same drive is `/dev/sda5`. Remember that the extended partition, that is, the primary partition holding the logical partitions, is not usable by itself.

The partitions on each disk are represented by appending a decimal number to the disk name: `dasda1` and `dasda2` represent the first and second partitions of the first DASD device in your system.