Linux System Administration Recipes A Problem-Solution Approach

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CHAPTER 1 ■ SAVING YOURSELF EFFORTmy $debug = 1; # set to 0 to turn off debug outputprint "At step 1\n" if $debug;This may seem like too much hassle for a quick-fix script—I admit I don’t always bother myself. Butyou will be very grateful to yourself in three months’ time if you do it. To make it easier, set up an alias inyour editor to insert if $debug;. For vim, add this line to your .vimrc:iab db if $debug;For emacs, type $debug in an open document, and then type C-u 2 C-x a g db (this adds the wordbefore the cursor as a global abbreviation). You’ll also need to type M-x abbrev-mode to turn on abbrevmode.Then, in whichever of vim or emacs you’ve set up, when you’re editing your Perl script and want totype a print line, type db (then hit Enter) at the end of it. Thus, the following:print "Reached point 3",db;will be expanded to this:print "Reached point 3" if $debug;A mere two keystrokes generates a massive timesaving later when you don’t have to either reinsertall your debug output or go looking for comments.1-8. Version Control: Using Subversion AliasesIt’s a good idea to keep more or less every file you touch in version control. For config files, you maywant to tie this in with your centralization setup (see Chapter 2). On a smaller level, you can use aversion control system for your own scripts, notes, and documents. Using version control, if you makean edit to a file and then realize that you deleted stuff you wanted to keep, you can still get it back! (Thishappened to me recently—I accidentally erased 50 percent of a nearly complete 4,000-word article anddidn’t realize until I went to finish it. I retrieved the previous version from Subversion, and that oneincident has more than made up for any minor time impact that using version control has day to day.)But, being lazy means trying to reduce that minor time impact still further. If nothing else, the easieryou make this for yourself, the more likely you are to use it regularly, which is what you need in order tomake it useful. The following applies to Subversion, which works in much the same way as CVS but withsome of the more irritating aspects of CVS removed. The excellent online documentation should get youstarted if you aren’t already familiar with it; I’m not going to go into the basics of using Subversion here.Here are a couple of aliases to reduce your typing. Add this to your .bashrc file:alias sva='svn add'alias svc='svn commit -m'alias svs='svn status'The first two aliases both need an argument after them.sva file.txt will schedule file.txt to be added to the repository.svc "Commit message" will commit with the given message.10Download at WoweBook.Com
CHAPTER 1 ■ SAVING YOURSELF EFFORTalias svs='svn status' just outputs the status of the current directory, showing which files aremodified and which haven’t been added. It’s a good idea to get into the habit of doing this before yourun a commit; plus, it reminds you of what you’re about to commit so you can write a useful commitmessage.1-9. Version Control: Adding Labels to Subversion LogMessagesSomething that can be an issue when using Subversion is that the default svn log command won’t showyou what files were changed in each commit; it shows only some revision information and the logmessage. svn log -v gives path information, or you can add more information to the log message itself.For example, say you have three big projects that you’re working on, A, B, and C; the following script willadd labels for them:01 #!/usr/bin/perl -w02 # svnl.pl: script to add labels to SVN commit message03 # usage: svnl.pl A|B|C “commit message”04 # Juliet Kemp 23.03.20090506 use strict;0708 die 'usage: svnl.pl A|B|C "commit message"' if $#ARGV > 1;0910 my $label = $ARGV[0];11 my $msg = $ARGV[1] || "";12 my $project;1314 if ( $label eq "A" ) { $project = "Project Able:"; }15 elsif ( $label eq "B" ) { $project = "Project Beta: "; }16 elsif ( $label eq "C" ) { $project = "Project Code:"; }17 else { $project = "Other: $label"; }1819 `svn commit -m "$project $msg"`;Note that this script allows for the usage svnl.pl "message text". In this case, $label = "messagetext" (line 10, since message text is the first and only argument) and $project = "Other: message text"(line 17), so that is what’s committed as the log message. Your labels can be as simple or as complicatedas you like.1-10. Version Control: Adding Multiple Files to SubversionOccasionally, you’ll find that you have a large stack of files to add all at once. sva * will add everything inthe directory and just give you a warning message about anything that’s already there. But first, that’s abit untidy, and second, you might not want to add everything.The following script, which must have a commit message as an argument, will look for all the filesthat haven’t been added to the repository, ask you whether you want to add each one (you can shortcut11Download 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
Page 23 and 24: CHAPTER 1 ■ SAVING YOURSELF EFFOR
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Page 41 and 42: C H A P T E R 2■ ■ ■Centraliz
Page 43 and 44: CHAPTER 2 ■ CENTRALIZING YOUR NET
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CHAPTER 2 ■ CENTRALIZING YOUR NET
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C H A P T E R 3■ ■ ■Monitorin
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CHAPTER 3 ■ MONITORING AND UPDATI
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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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CHAPTER 7 ■ WORKING WITH APACHEdi
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CHAPTER 7 ■ WORKING WITH APACHE4.
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CHAPTER 7 ■ WORKING WITH APACHE
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CHAPTER 7 ■ WORKING WITH APACHEAl
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CHAPTER 7 ■ WORKING WITH APACHE
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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 BUGS
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CHAPTER 11 ■ TRACKING DOWN BUGSTh
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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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