When run as a daemon, hddtemp needs to call setsid() to switch to a new session. Otherwise, when /sbin/init uses a tty other than /dev/tty, hddtemp will be killed at the end of the system boot-up. This can happen when CONSOLE=/dev/tty1 or similar is added to the kernel command line.
Created attachment 54362 [details, diff] A patch that adds the setsid() call.
Fixed in 0.3_beta13.