To check hardisk information such as model and serial number, there are a few useful commands like hdparm, sdparm and fdisk.

To check the information about first hardisk for PATA and SATA hardisk:

hdparm -i /dev/sda

For SCSI disk, a different command is to be used:

sdparm /dev/sda

To check the hardisk capacity and partitions contained in the hardisk, fdisk can be used:

fdisk -lu /dev/sda