When Linux boots, it displays a few messages, one of the most important being a partition check. You see messages like the following:

Partition check:

hda: hda1 hda2 hda3

hdb: hdb1 hdb2
In this example, the first non-SCSI disk has three partitions and the second disk has two. Your system’s output is probably different, of course. If you don’t see any partition information, either the hard disk controller is not recognized properly or the disk drives are not accessible. Check the following potential causes for these problems:

Check the cables inside the computer. The hard disk cable should run from the adapter card to each drive’s connector. Make sure the cables are connected in the proper manner (the red strip on the cable is at pin 1 on the connector).

Check that the power connector is attached to each disk drive. Without power, your drive doesn’t spin up and Linux can’t touch it.

Check the partition table to make sure you created a Linux partition properly.

If the drive is still not working properly with Linux but works OK when you boot DOS, a kernel driver for the hard disk is likely at fault. Some IDE drives, for example, are not as well-behaved (not conforming to the IDE standards) as others, and your IDE kernel driver may not be able to talk to your drives. Try using a different kernel image and see if the problem solves itself. If you are using a SCSI kernel and adapter and the drives are not recognized, use the utilities that came with the SCSI adapter card to force a check of the hard drives. They may have a SCSI ID set incorrectly.