Linux System Administration Recipes A Problem-Solution Approach

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CHAPTER 1 ■ SAVING YOURSELF EFFORTSimilarly, if you’re implementing something on box 1 and one of your interim tests also passes onbox 2, which you haven’t changed, then you may be doing more work than you need to do. This isparticularly true when working on client-server software, when a change to the server can affect all theclients without you having to do any more work. Checking against your comparison client can find thesesorts of problems.Testing regularly can also be a useful part of a system monitoring setup; see Chapter 3 for more onsystem monitoring.1-16. Reinventing the WheelWhen you come across something that needs to be fixed or implemented, it can be very tempting tocrack straight on with rolling your own solution. Writing stuff yourself is fun, and it can seem a lot moreappealing than the process of looking for a solution that already exists, checking that it really does dowhat you want it to, getting it installed, and so on.Here’s some reasons why you should ignore the impulse to reinvent the wheel and instead shouldtake yourself to Google, reread this book, check out the many others available for specific or broaderadmin topics to see whether they have anything useful to say, or solicit recommendations from othersysadmins:• It’s quicker. It may feel like less interesting work, but it really will be quicker thangoing through the design-implement-test process.• More support is available—even just a couple of users (and most existing projectswill have more than that) is a couple more than your self-constructed tool, andthat’s a couple more people than just you to get input from when something doesgo wrong.• When eventually you move on to bigger and better things, the person whoreplaces you will have more chance of picking the tool up smoothly and may evenhave previous experience with it.• Documentation should already exist, so you won’t have to write it yourself! (OK,this isn’t always an absolute guarantee with open source software, unfortunately,but there should be at least some. And if you do have to write more, you can get anice warm altruistic glow by making it available to the rest of the usercommunity.)• If it really doesn’t have everything you want, you can patch it—without having towrite everything from scratch. And again, you can hand that over to thecommunity as well.• Someone else has done all the testing for you.This list applies to things like Perl modules (CPAN, which is great in many ways but is sadly unrated;try http://cpanratings.perl.org/ to get more information on modules). Use other people’s hard workso that you can direct your own hard work more usefully.18Download at WoweBook.Com
CHAPTER 1 ■ SAVING YOURSELF EFFORTCPAN is an enormous collection of free Perl modules—reusable Perl toolboxes in effect. There’s apain-free installation method, as described in the main tutorial on the site. If you’re writing Perl at allregularly, it is well worth checking out. Because anyone can upload to CPAN, quality does vary, butthere’s good stuff there, and the documentation can be very helpful. At its best, it can save an awful lot ofwheel reinventing.To identify the most valuable CPAN modules, helpful options are checking the “kwalitee” scores onthe CPAN Testing Service page (http://cpants.perl.org/kwalitee.html), looking at the recommendedCPAN modules on the Perl Foundation web site (http://www.perlfoundation.org/perl5/index.cgi?recommended_cpan_modules), and checking out the CPAN ratings (http://cpanratings.perl.org/). Google can alsobe useful.SourceForge (http://sourceforge.net) also has stacks of <strong>Linux</strong> software projects available for freeand is well worth checking out. Freshmeat (http://freshmeat.net) maintains the Internet’s largest indexof Unix and cross-platform software.Situations where this might not apply include working environments where there are security orlicensing issues with using open source software or when you’re trying to learn a new language and thewheel reinvention is just a means to an end. And, OK, sometimes you’re just in it for the fun. Never let itbe said that I have anything against fun.19Download at WoweBook.Com
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Page 7 and 8: Contents■About the Author .......
Page 9 and 10: ■ CONTENTS3-7. Writing a Nagios P
Page 11 and 12: ■ CONTENTS■Chapter 8: Using the
Page 13 and 14: ■ CONTENTSAbout the Author■Juli
Page 15 and 16: ■ CONTENTSAcknowledgmentsMany tha
Page 17 and 18: ■ CONTENTSIntroductionThis book i
Page 19 and 20: ■ INTRODUCTIONDownloading the Cod
Page 21 and 22: C H A P T E R 1■ ■ ■Saving Yo
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C H A P T E R 4■ ■ ■Taking Ba
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CHAPTER 4 ■ TAKING BACKUPS AND MA
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C H A P T E R 5■ ■ ■Working w
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CHAPTER 5 ■ WORKING WITH FILESYST
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C H A P T E R 6■ ■ ■Securing
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CHAPTER 6 ■ SECURING YOUR SYSTEMS
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CHAPTER 7 ■ WORKING WITH APACHEOn
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C H A P T E R 8■ ■ ■Making Be
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CHAPTER 8 ■ USING THE COMMAND LIN
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CHAPTER 9 ■ WORKING WITH TEXT IN
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C H A P T E R 10■ ■ ■Things G
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CHAPTER 10 ■ THINGS GO IN, THINGS
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C H A P T E R 11■ ■ ■Tracking
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CHAPTER 11 ■ TRACKING DOWN BUGSTh
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CHAPTER 11 ■ TRACKING DOWN BUGS01
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CHAPTER 11 ■ TRACKING DOWN BUGSAn
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CHAPTER 11 ■ TRACKING DOWN BUGS#
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C H A P T E R 12■ ■ ■Managing
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CHAPTER 12 ■ MANAGING TIME AND PE
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APPENDIX■ ■ ■Perl TipsSee rec
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APPENDIX ■ PERL TIPS• Date::Par
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APPENDIX ■ PERL TIPSPerl Syntax N
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■ ■ ■Index■Symbols$CDPATH,
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■ INDEXenscript option (printing)
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■ INDEX■NNagiosadding hosts to,
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■ INDEXsyslogcentralized logging
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