HMC Mathematics Computing Weblog

As announced in November, 2005, support for the use of PHP, a popular, but problematic, web-programming language, has now ceased.

Any pages that relied on the Apache PHP module being available will no longer render properly.

If the lack of PHP poses a problem for you, please let me know and we can look into alternatives that pose less of a security risk for our system.

I have converted and updated the old Beowulf cluster documentation to match the mathematics and computer-science departments' current cluster, Amber.

I have not yet been able to test and verify all of the example code provided on the old site, but the code that does work properly is included, along with links to upstream documentation.

Please note the new policies and account-request process. Amber accounts require a standard math-cluster account (as Amber nodes are, basically, standard math cluster nodes with some additional software).

If you have comments or questions, please send them to beowulf at math.hmc.edu.

I've updated the version of Firefox in /shared/local to 1.5, which is the latest release.

You can run Firefox by typing firefox at a terminal prompt or by creating a GNOME Panel launcher by right-clicking on a panel, choosing Add to Panel, then choosing Custom Application Launcher and filling in the fields in the dialog box that will appear.

You can find a Firefox icon in /shared/local/firefox/icons. The canonical path to the application until such time as it is installed by default on individual machines is /shared/local/firefox/firefox. For most people (unless you've tinkered with your PATH), just putting firefox in the Command field will do the trick.

Among other improvements, Firefox 1.5 supports RSS, Atom, and other feed protocols in a much more convenient way than previous versions of Firefox did.

Despite the dramatic-sounding title of this entry, I expect that there will be little or no actual change in the way that the system works for about 99% of the affected users.

As another short-term way of dealing with the ongoing disk space crisis on /home/faculty, I have migrated the emeritti and former-faculty accounts that had their home directories in /home/faculty to a new partition on the server.

Practically speaking, there should be no real impact from this change for anyone, even the people whose accounts were moved, as I have added links to preserve the appearance of the file system.

If your account has been moved (you can tell by logging in and running pwd, which will tell you your present working directory) and you notice some issues, or if you try to reach a personal web resource (i.e., one that has a URL similar to http://www.math.hmc.edu/~someaccount) that is no longer available, please report the problem to me so I can track it down and fix it.

The Nitty-Gritty Details

If you're interested in the details of what was done, most of it is pretty visible, kind of like post-surgical scars.

/home/guests is now a link farm, with symbolic links pointing to actual directories that are located in /home/guests-one or /home/guests-two. The account database has been set up so that home directories for migrated accounts are in /home/guests (that is, they point to the links that point to the real directories).

Because of the limitations of NFS, we now have to export /home/guests, /home/guests-one, and /home/guests-two, and mount all three of those shares on each machine that is available for general use.

The original directories in /home/faculty have been replaced with links that point to the directories in /home/guests, so any web-related links will still work.

Potential Issues: Hard-Coded Home Directory Paths

Because of the links, everything should work as it always has. At some point down the road, however, I hope to be able to add some additional disk space, which will allow me to do some rejuggling of account locations. At that point I will probably try to clean up some of the remaining links to make everything neat and less complex.

With the removal of the links, scripts or other materials that refer to hard-coded, complete paths to your home directory or directories within your home directory may break. In other words, if you had a script that looked for files in your home directory and specified them as

/home/faculty/username/some/directory/or/file

(where username is your username), but your physical home directory is now located in /home/guests-two/username, and is referred to by the system as /home/guests/username, you will have problems when one or more of the links is removed or changed.

If you're working with shell scripts, the best way to refer to your home directory is with the environment variable $HOME, which is pretty much guaranteed to resolve to the correct answer no matter what shell you or your script use. For many modern shells (and scripts written in those shell's language), you can use the tilde (~) to refer to your home directory, but $HOME is safer and more likely to work no matter what. (You'll want to use ~ on the command line, of course.)

The Future: Solutions in the Pipeline

This mess will be cleaned up after we've obtained more disk space, which is on the agenda for a departmental computing-committee meeting on Friday. I hope that we will be able to find the money to move quickly on that project, and that I will be able to put additional disk space online over spring break (March 10 - 19).

In the meantime, keeping an eye on your disk usage and avoiding excessive disk usage (which I would define as usage that's significantly more than others with home directories in your partition) is, and will always be, a good thing to do that will benefit everyone else all the time, and you when you have a sudden, short-term need for a larger amount of disk space.

Thanks for your cooperation.

Version 1.5 of Mozilla Thunderbird, the Mozilla Foundation's e-mail client, was released today.

I have installed it in /shared/local/thunderbird, where it takes the place of the previous release (which was 1.0.7). The old release will still be available in /shared/local/thunderbird-1.0.7 for at least a couple of weeks.

Please enjoy the new release, and let me know about any problems that you have with it.

Apple's CEO, Steve Jobs, gave the keynote at MacWorld 2006 this morning. The highlights of his presentation were

• The iMac being updated with the new Intel Core Duo processor; it's the same machine in every respect except for the processor. According to Jobs, the top of the line iMac, with a 2 GHz Intel processor, is twice as fast as the 2 GHz PowerPC G5 version. Now sells for $1499 educational (base price).
• New versions of iLife and iWork. It seems like the iWork apps (Pages and Keynote) were updated a bit, but there are no new apps. The iLife bundle has updates to iMovie, iDVD, and GarageBand (including a new Podcast Studio for making your own podcasts). It also has a brand new app, iWeb, which allows you to create and maintain websites. As this app is brand new, there's no feedback on what sorts of HTML it produces, but we can hope that Apple has done the right thing and is creating clean, valid XHTML or XML and valid CSS. Both of these packages are $79.
• Of most interest, as usual, was Jobs's ``one more thing'' -- a new laptop computer using the Intel Core Duo processor, the MacBook Pro. This computer is essentially a drop-in replacement of the existing 15" G4 PowerBook -- it has the same size and weight as the PowerPC version. But it runs four times faster than the top of the line PowerPC version, and presumably also picks up some advantages in terms of battery life and heat production by using Intel's mobile CPUs, which are optimized to reduce power use and heat production. The MacBook Pro also features a built-in iSight camera and microphone (like the iMacs) and has a clever new power connector that makes it slightly less likely that someone will trip over your power cord and yank your machine off a table or desk. The MacBook Pro has two models, both with the new 15.4" screens with the same resolution as the older 17" PowerBook. The 1.67 GHz Core Duo model starts at $1799 educational; the 1.83 GHz machine starts at $2299 educational.
• Finally, Mac OS X 10.4.4 was announced for release via Software Update. The new OS version includes all the support necessary for the new Intel machines, and throws in some bug fixes and new widgets for those of with older machines.

For anyone disappointed that they missed out on getting a new Intel-based machine in the most recent round of purchases, let me point out that as the processor has changed, older PowerPC software has to run through an emulator that Apple calls Rosetta. Rosetta is meant to be reasonably fast (especially with the newer, faster processors), but you would still see a significant performance hit when running older software.

Apple's own software is now shipping as ``universal binaries'', as is software produced by various smaller companies. Many of the larger players, however, such as Microsoft and Adobe, have yet to ship universal versions of their products. Even if they started shipping these today, they would probably update the very newest versions of their software -- older versions that work just fine would not be updated. The same issues apply for much of the software provided by CIS, most of which is not the very latest-and-greatest version.

My personal comments on the MacBook Pro: It looks very, very cool. I was very interested in the improved screens on the last refresh, in which the 15" and 17" PowerBooks had dramatic increases in the number of pixels that they could display (the 15" model ended up with the same number of pixels the old 17" PowerBook had; the new 17" PowerBook had the same number of pixels as Apple's 20" desktop display).

But the 15" PowerBook and MacBook Pro are still pretty big machines. Both weigh 5.6 pounds, a full pound more than the 12" model. If you're a big guy, 5.6 pounds isn't that much, but if you're me, 5.6 pounds is a lot, especially combined with the rest of the stuff I end up carrying around. I think I'll have to see it before I'm completely sold on it, and I'm hoping that Apple will figure out that there are a lot of people who need or want performance but who don't need a huge screen and the extra weight that brings you. (Hey, I plug my 12" laptop into a 20" monitor when I need a bigger screen -- it works great.)

Also, beware the lure of the first generation of Apple products. Traditionally, Apple has been on the cutting edge with the coolest new gadgets. Unfortunately, also traditionally, these first-generation models have almost always had various issues that affect their performance in some way. The sound advice is to let other people be the first adopters, and pick up new stuff after Apple's had a chance to work out some of the bugs.

That said, four times faster sounds awfully good.... ;-)