Disk temperature is a fairly important issue, affecting, among other things, disk lifespan.
hddtemp is a program that displays the temperature of a hard disk. It can run in daemon mode (i.e. run in the background, independently of the user).

• Running the program once

• hddtemp disk
  where disk is e.g. /dev/hda,/dev/sda

  hddtemp /dev/hda
  /dev/hda: ST380021A: 38 C

  If hddtemp shows us this kind of result, it means it's working; if not, either our hddtemp database is out of date , or our disk doesn't support S.M.A.R.T. and there's no way to read the temperature.

• Running hddtemp in daemon mode

• we need to locate the configuration file, which is called hddtemp; we can use the command for this:
find /etc/ -name hddtemp
• we change the following listed entries in it:

# hddtemp network daemon switch. If set to true, hddtemp will listen
# for incoming connections.
RUN_DAEMON="true"
# List of devices you want to use with hddtemp. If none specified,
# hddtemp will probe standard devices.
DISKS="/dev/hda /dev/sda"
	

• we start our program with the startup script (on debian /etc/init.d/hddtemp start)
• if for some reason our distribution doesn't have this script, we can always run the application with the -d option
hddtemp -d /dev/hd[a-z]
which will run the application in daemon mode, checking the temperature of all available disks,
• if we want hddtemp to start on computer reboot, just add the command to rc.local
echo "hddtemp -d /dev/hd[a-z]" >>/etc/rc.local
• to read the temperature after the above operations we can use programs like netcat or telnet
nc localhost 7634 or telnet localhost 7634

|/dev/hda|ST380011A|39|C||/dev/hdc|ST3120026A|42|C|

Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
|/dev/hda|ST380011A|39|C||/dev/hdc|ST3120026A|42|C|Connection closed by foreign host.