Mick—thanks for your Paranoid Penguin columns; I always open my new issue of LJ right to it to see what you've got in store each month. The “Hardening Sendmail” article [LJ April 2002] was another winner. I just wanted to point something out regarding your recommendation not to run a sendmail dæmon if only sending mail. I used to do just that but found something unfortunate: if a send attempt fails, then sendmail could queue it for later delivery. If the sendmail dæmon wasn't running, well, “later” would never come. I wouldn't know about the failed delivery (especially without the usual informative messages from sendmail after four hours, and after five days). So, I run sendmail (postfix, actually). If you've got a better solution, I'd love to hear it. And I'm sure other readers would, as well.
Mick replies: Thanks for the kind words! You're right, if sendmail isn't running as a dæmon, queued mail will remain queued indefinitely. I should have mentioned that common practice is to set up sendmail to be run from cron periodically with the -q flag. For example, this sample crontab line (adapted from one in Olaf Kirch's Linux Network Administrator's Guide) invokes sendmail in “flush queue” mode every 15 minutes:
0,15,30,45 * * * * /usr/sbin/sendmail -q
Obviously, that has to be in the crontab of an account authorized to run sendmail this way—usually root. And depending on how much outbound mail you deal in, you may not need to run sendmail every 15 minutes—hourly may suffice. Postfix most definitely rocks, by the way. And my friends who use qmail *really* like qmail.
I was surprised to see your article about P3P in the April 2002 issue of Linux Journal. Since 1999, P3P has been shown to be orthagonal to privacy, despite claims made to the contrary. I don't really see that the W3C has done a lot to allay fears of P3P. P3P is overly complicated and is geared toward collection of user information, not protection of it. The only serious difference between P3P and non-P3P sites is convenience in giving away your personal information. It's not even a legal help: just because a company does something illegal does not mean the average Joe can do anything about it.
The protocol could be greatly simplified and need not have any information about the user at all. Also, even if the protocol forces contact information to be given to the user, there is no easy method for the browser to determine its validity, and it is no guarantee the company will listen. In other words, “same ole same ole”, but more complex. A protocol that really is designed to protect users' privacy will never need to know anything about users except their privacy preferences. There is absolutely no need for other information, yet P3P includes a large amount of detailed and personal user information. You have to ask yourself why this has been made so complex and so heavily geared toward data acquisition.
I have been a Linux user since Red Hat 4.2 and picked up my first LJ about two years ago. I have always poked about in all the different directories and have always wondered “What is really required here?” I mean, what is the minimum requirement for a working Linux distribution, without any user apps, just something that loads, prompts for a login, then takes you to a shell prompt and lets you log off or shut down. No lynx, no elm, no sendmail, no anything. I have always thought it would be a great personal educational undertaking for myself to attempt to create my own distribution...but I've no idea where to begin.
Yes, you can build a tiny distribution with just a kernel and a shell. You might want to start with Brian Finley's “Brian's Own Embedded Linux” and remove software from it. BOEL fits on a floppy, and two articles about it appear on embedded.linuxjournal.com. See www.linuxdevices.com/articles/AT9049109449.html and www.linuxdevices.com/articles/AT5974781081.html.
Practical Task Scheduling Deployment
July 20, 2016 12:00 pm CDT
One of the best things about the UNIX environment (aside from being stable and efficient) is the vast array of software tools available to help you do your job. Traditionally, a UNIX tool does only one thing, but does that one thing very well. For example, grep is very easy to use and can search vast amounts of data quickly. The find tool can find a particular file or files based on all kinds of criteria. It's pretty easy to string these tools together to build even more powerful tools, such as a tool that finds all of the .log files in the /home directory and searches each one for a particular entry. This erector-set mentality allows UNIX system administrators to seem to always have the right tool for the job.
Cron traditionally has been considered another such a tool for job scheduling, but is it enough? This webinar considers that very question. The first part builds on a previous Geek Guide, Beyond Cron, and briefly describes how to know when it might be time to consider upgrading your job scheduling infrastructure. The second part presents an actual planning and implementation framework.
Join Linux Journal's Mike Diehl and Pat Cameron of Help Systems.
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- Managing Linux Using Puppet
- Non-Linux FOSS: Caffeine!
- Doing for User Space What We Did for Kernel Space
- SuperTuxKart 0.9.2 Released
- Google's SwiftShader Released
- Parsing an RSS News Feed with a Bash Script
- SourceClear Open
With all the industry talk about the benefits of Linux on Power and all the performance advantages offered by its open architecture, you may be considering a move in that direction. If you are thinking about analytics, big data and cloud computing, you would be right to evaluate Power. The idea of using commodity x86 hardware and replacing it every three years is an outdated cost model. It doesn’t consider the total cost of ownership, and it doesn’t consider the advantage of real processing power, high-availability and multithreading like a demon.
This ebook takes a look at some of the practical applications of the Linux on Power platform and ways you might bring all the performance power of this open architecture to bear for your organization. There are no smoke and mirrors here—just hard, cold, empirical evidence provided by independent sources. I also consider some innovative ways Linux on Power will be used in the future.Get the Guide