Monthly Archives: February 2013

Saving energy with Raspberry-pi display screens

The University runs a campus messaging service, displaying a slideshow of University information and more general news in rotation. There are a number of such displays dotted around campus. We have one in the school office.

Traditionally, this display has been driven by an off-the-shelf PC. Due to where the screen was situated, this meant running trunking up above the ceiling tiles and across the office to the nearest convenient place that the PC could be housed. It also meant we had an aging PC on all the time, consuming energy.

During the Christmas break CS support experimented with replacing this PC with a Raspberry Pi. To the uninitiated, a Raspberry Pi is a credit-card sized, low powered embedded computer which has been designed principally to promote programming to children. The current Pi model draws approximately 3½ Watts and can be situated directly behind the screen.

The main OS for the Pi is a derivation of Debian GNU/Linux called Raspbian. It turned out to be quite simple to customize a stock Raspbian image to make it suitable for campus messaging. There are a number of existing customisations for running display screens but unfortunately none that we found were quite suitable.

I hope we are able to soon share our customisations so that they are available to both the wider University and anyone else who may be interested in running display screens in this way.

Computing Science Website Update for Feb 2013

Staff Profile Information

We are currently in the process of updating guest and visitor records/profiles by adding background information, e.g. the areas of research they are currently participating. We have started with the Visiting Professors where there were previously no details at all, and hope to add background information for all guest staff in the near future.

Here is an example of staff details we have updated:

Professor Gabriel Ciobanu

We have also improved the staff records on the website by ensuring that all staff have the same format/style of telephone number. Previously, most staff used the format +44 (0) 191 222 XXXX which is the standard notation for displaying international landline numbers. The compatibility with mobile devices such as the iPad – which auto-detect telephone numbers – is, +44 191 222 XXXX. Landline telephone numbers for all staff have been updated to this new format.

Visual Media

After trialling Vimeo for the storage and displaying of video media, we are now using it to present all videos which are displayed on the Computing Science pages, such as:

Internal Computing Science Pages

A new set of Internal pages have been setup for the School, which includes new and current staff information (e.g. Staff Handbook and Teaching information). Also, most of the archive records from the old internal site have been transferred to the new internal pages.


We have further updated our history/events page. As a contribution to the celebration of the Alan Turing Year, the School hosted an afternoon seminar for students, staff and the general public on 14th November, attracting an audience of almost 200. A page recording this event has been setup containing the details of the event and videos of slide/speaker presentations.

Machine room clear-out

D823 before
D823 after
D814 after

One of the major support projects last year was the Machine Room project: we closed two machine rooms down by migrating servers and services to a variety of different destinations, ranging from ISS-provided virtual machines to moving our physical machines into racks in the University’s main data centre, SB12. The result was large capital savings to the University in terms of energy usage; the school has avoided spending a lot of money on refurbishing or replacing the aging aircon and UPS infrastructure; we’ve also reclaimed 130m² of space to re-develop for postgraduate teaching.

At the beginning of this week, the final rack was removed from the (formerly) main machine room D823. This rack held the network infrastructure and required a little more work to full decommission than the server racks that used to sit adjacent to it. With the final rack gone, the contrast between the room when fully populated and now is quite startling.

I took some panoramic pictures using a free iOS app by Microsoft called photosynth. Photosynth stitches together a collection of photographs into a panorama. The results can then be shared on the web via the photosynth website, or flattened out into a picture that looks like it was taken with a fish-eye lens.

The flat pictures are embedded in this blog post, but you can also pan around the full panoramic images of “after” via the photosynth website: D814, D823.

Maximum process lifetime on the Mill cluster

There’s a bug in the version of gnome-shell which we run on the Mill cluster. Occasionally on logout the process does not exit properly and instead starts “spinning” in a busy loop. This does not appear to stop others from using the machine locally, but does impact the performance of compute jobs scheduled to run on the cluster during Evenings.

To address this in the short term, we’ve developed a policy that automatically kills any user process that has been running for more than 24 hours. It’s quite possible that this will impact people who are using the Mill to run longer-term jobs. If so please get in touch with us. We can look at “whitelisting” particular users, or alternative ways of running your jobs.
This policy is now live on mills mill010 through to mill019. I hope to apply it to the entire cluster by the end of the week.

Longer term we hope that this bug will be resolved properly when we upgrade the Mill cluster to a newer version of the Fedora operating system.

Please let me know if you experience any problems on the Mill cluster, in particular on any numbered between 010 and 019 inclusive.