Letters to the Editor

Readers sound off.
Power Failures?

I like LJ, especially the articles on “real world” applications of Linux, as well as those on how some of the software works (e.g., majordomo, Tcl/Tk, RCS) and on how to do things (connect to the Internet).

I don't actually have Linux yet. Truth is, I don't have a computer yet, but I am putting a plan for getting one before the Household Steering Committee soon. Wish me luck.

I do have a major question about Linux. I know that, with Unix, and unlike DOS, you just don't unplug your computer or switch it off. I believe the procedure is to do a “sync” before shutting it down. I presume Linux is the same. What happens when we have a power out(r)age? What kind of a mess will I have to clean up, what data could I lose, and how can I protect myself? Is tape backup the only way? How about a power-failure detection system? A daemon to do periodic syncs? Perhaps LJ could run an article on cost- and time-effective ways to ensure maximum up-time and minimum disaster potential.

—Charles L. Hethcoat III

We do wish you luck in your hearings before the Household Steering Committee.

What is missing from your question is what happens to MS-DOS machines if they are in the middle of disk access during a power outage. It turns out that the standard “ext2fs” filesystem under Linux is more stable in the face of disaster than the DOS filesystem. Given the same usage patterns, a Linux machine is much less likely to loose files and data than a DOS machine.

If properly configured, a Linux machine automatically checks when it boots to see if it was cleanly shut down. If it was not, it automatically checks the filesystems to make sure that they are not damaged, and fixes them if they are damaged.

Those who use DOS's SMARTDRV write-caching also have to do the equivalent of a sync before shutting off their computers.

Unix has always had a daemon, called update, to do periodic syncs. Linux also has it.

The one thing (besides backing up, which is always the first point of defense) that will almost entirely prevent any filesystem damage is a quality uninteruptable power supply (UPS). In the 9 months that I have had my computer connected to a UPS, I have not lost a single file due to any of the frequent power failures in my area. To be fair to the Linux filesystem, I had only ever lost one file to a power loss—and even that may have been user error.

UPSs range in price from around US$100 to US$1000 for reasonable choices for home and small business use, and will save you from almost anything save a direct lightning strike, from which only off-site backups will protect you. Most UPSs have a connector (usually at extra cost; some connectors you can make yourself if you are technically inclined) that can report power loss to a program running on the computer. We do intend to have an article on that, written by someone who has significantly enhanced the Linux powerd daemon.

Where Credit is Due

I wish to thank you for the coverage you gave to our Linux sessions in DECUS at Washington D.C.

About the only change that I would make to the article is to publicly recognize the efforts of Kurt Reisler, Chairman of the Unix Special Interest Group of the U.S. Chapter of DECUS.

Kurt first pointed out the interest in Linux to me and suggested that Linus come to New Orleans DECUS. Kurt's efforts “inspired” me to fund Linus' first trip to DECUS, which consequently drove the funding of the Alpha system for Linus to start his port. Kurt directed the schedule for DECUS in D.C. as well as hosting most of the Linux activities. Kurt has been a tireless advocate of Unix for as long as I have known him, which is over ten years.

I ask that you print this letter, as I believe very strongly in credit where credit is due.

Jon “maddog” Hall, Senior LeaderUNIX Software Group, Digital Equipment Corporation

Mea Culpa! Kurt's efforts certainly deserve recognition and respect, and I was amazed to re-read my article and find that I had left out any mention of him. Thank you very much for bring this mistake to my attention. I apologize profusely.

Three Dimensions

I just received the July issue of LJ. My only complaint is that it's so good, I rip through it as fast as I can! The reviews of X servers are well-timed. Also, (I work in a virtual reality lab) I think you need some reviews of the OpenGL ports available. Perhaps an explanation of them, and some of the other (free) 3-D renderers out there (Mesa, etc). Maybe even an article on writing 3-D applications under one of the packages...

Also, Greg's article on X setup is beneficial to say the least! Every time I help set up someone's X windows, they ask me how I learned all that; I reply, “The hard way!” The interview with Mr. Zborowski is good; not too many people know the roots and beginnings of the software packages they're using.

Good work!

Trent Tuggle, tuggle@vsl.ist.ucf.edu

I'm glad you find LJ useful. We do plan to have reviews of the OpenGL ports, and we have a standing request for a Mesa developer to write an article on Mesa, which already looks very good and shows a lot of potential for further development.


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