The /dev/hd[egik] device nodes were owned by root:disk and 660. However, the hddtemp binary was trying to do some restricted ioctl operations. Even though the binary was setuid and my non-root user was in the disk group I couldn’t access the disk to get the temperatures.

I found out that there is a hddtemp daemon which can query the disks for my unpriveleged user.

The daemon listens on a TCP port and provides output like this:

|/dev/hde|ST3160811AS|39|C||/dev/hdg|ST3160811AS|40|C||/dev/hdi|ST3160811AS|38|C||/dev/hdk|ST3160815AS|39|C|

Should be easy to modify my disk_temperature.rb to connect to that port and parse the data.

Now my temperature graphs will have new data (as soon as the change is made).

I can easily use S.M.A.R.T. to monitor the temperature and the hddtemp Linux utility to get the temperatures of the disks.

It’s easy to use a crontask to poll the disks and to stuff the temperatures into an rrdtool database. I drew much inspiration from Martin Pot‘s Perl script to do the same thing but implemented my own in a Ruby Rake task using the woefully undocumented RubyRRDtool gem and a custom hddtemp wrapper class to get the temperatures.

The similarities between my Rake task and Martin’s RRDtool-fu is obvious, however I wanted an hour graph too and so I added it in on line 17.

My next task is to combine the temperatures (lines) of all four disks into a single graph to get a feel for the overall temperature of the disks on one image.

The graphs can be seen at my personal website.