Device names in Linux
The disk names in Linux are alphabetical. /dev/sda is the first hard drive (the primary master), /dev/sdb is the second etc. The numbers refer to partitions, so /dev/sda1 is the first partition of the first drive.
hda – stands for an PATA (Parallel ATA) Hard-disk a
sda – stands for an SCSI Hard-disk a + SATA + USBsda1 for example, it would mean the first partition of the SCSI drive a.
hda1 = first partition of ide drive a.
hd0 – Harddrive (not depending on the Hardware) id 0.
hd0-1 Harddive 0 partition 1.
/dev/ is the part of the Unix directory tree that contains all “device” files — Unix traditionally treats just about everything you can access as a file to read from or write to.
sd originally identified an SCSI device, but since the wild growth of USB (and other removable) data carriers it became a catch-all for any block device (another Unix term; in this context, anything capable of carrying data) that wasn’t already accessible via IDE. When SATA came around, the developers figured it’d be much easier and much more convenient for everyone to add it to the existing framework rather than write a whole new framework.
The letter immediately after sd signifies the order in which it was first found — a,b,c…z, Aa…Az… etc. (Not that there are many situations in the real world where more than 26 discrete block devices are on the same bus…)
What is dev/sda in Linux?
- dev/sda – The 1st SCSI disk or simply Hard Disk..
- dev/sdb – The 2nd SCSI disk.
- dev/sdc – The 3rd SCSI disk.
- dev/hda – The master disk on IDE primary controller.
- dev/hdb – The slave disk on IDE primary controller.
The last two digits are usually more significant than the first two:
sda5 = 5th partition on the first HD (‘a’ is first HD)
sdc8 = 8th partition on the third HD (‘c’ is third of three active HDs)
sdb3 = 3rd partition on the second HD (‘b’ is second of two or more active HDs)
what is meant by (hd0,1)?
Grub is a bootloader.
A bootloader is a program that is found by the system BIOS in the boot sector of your storage device (hard drive’s Master boot record), and which locates and starts your operating system for you.
Grub has its own format/syntax for finding an HD location that’s different from the syntax the Linux OS uses:
(hd0,5) = sda5
(hd2,8) = sdc8
(hd1,3) = sdb3
Not to be confusing, but Grub is still going through a transition from the original grub, Grub legacy, to Grub2, a rewritten and updated version. In the above example, the syntax is correct for Grub2 but incorrect for Grub legacy. Most distros now use grub2 but not all of them.