hddtemp is used to monitor hard drive temperature.

Install it with
[@
% sudo apt-get install hddtemp
@]

Then you are ready to run it

[@
% sudo hddtemp /dev/hda
/dev/hda: ST3400620A: 37°C

% sudo hddtemp /dev/hdc
/dev/hdc: ST3400620A: 42°C

@]