Linux System Administration Recipes A Problem-Solution Approach

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CHAPTER 1 ■ SAVING YOURSELF EFFORT1-12. Subversion: Dividing RepositoriesYou can keep going for a long time with the basic stuff with version control—as long as you’reremembering to commit all your changes, you’re fine. However, eventually you may need to messaround a bit with your repositories. Dividing, branching, and merging repositories are all things thatmay be necessary at some point and are straightforward with Subversion.So, you’ve decided that your single repository would be better off as two repositories. Maybe youwant to divide the config files from your scripts or from your notes. Before you start, make sure allworking changes are committed (or you’ll lose them when tidying up afterward) and that no one else isgoing to commit to the repository while you’re moving things around.To get a list of the directories in the repository and decide what to move, type the following:svn list file:///path/to/repositoryThen use this to get a dump of the repository (which may take a little while if you have a largerepository):svnadmin dump /path/to/repos > repos.dump■ Note Although svn will use http:// or file:// repositories, svnadmin takes only a plain path. So, you can’tuse it on a repository that you have only remote access to. You have to be logged in on the machine where therepository actually lives.Next, create the directory for your new repository:svnadmin create /path/to/newreposThe tool svndumpfilter allows you to choose a particular directory or directories. The command youwant is as follows:cat repos.dump | svndumpfilter include testdir | svnadmin load newreposThis pipes the old repository through svndumpfilter, tells the filter to include only the testdirdirectory, and then loads it into the new repository. (You can specify multiple directories if required.)All that’s left to do after this is to tidy up. If /local/checkout/testdir is where your existing workingcopy of testdir is living, use this:rm repos.dumpcd /local/checkout/svn delete testdirsvn commit -m "Deleting testdir from repository"svn checkout /path/to/newrepos/testdir testdirThis deletes the dumpfile, deletes the migrated directory from the old repository, and checks aworking copy out from the new repository.14Download at WoweBook.Com
CHAPTER 1 ■ SAVING YOURSELF EFFORT■ Note Unfortunately, there’s no way in Subversion to remove a directory from the database altogether, in otherwords, including all of its change history; this recipe just deletes it from this point in time, with all the pastinformation still kept. If you want to erase it altogether, you’ll have to use svndumpfilter exclude to create anew repository without the unwanted directory. This code will do that:svnadmin create /path/to/new_main_reposcat repos.dump | svndumpfilter exclude testdir | svnadmin load new_main_reposAfter you’ve checked your new main repository, you can delete the old one altogether and then check everythingout again from the new one.1-13. Subversion: Branching RepositoriesThe canonical situation for coders where you’d want to branch is when you want to create a dev branchof a project so that the main fork can be the stable code. (Or vice versa.) For sysadmin purposes, it mightbe useful to branch your config file tree when you upgrade some machines to a different version of yourdistro—so you can also merge across changes from the main version when they apply and then mergethe whole branch back in when you upgrade the other machines.To create a new branch, you need to make a copy of the main project:svn copy /path/to/repos/proj/trunk /path/to/repos/proj/branchNow check out that new directory to start working on the branch, and that’s it:cd my_branch_dirsvn checkout proj/branchIn due course, you’ll probably want to merge the changes back into the main tree (for example,when all your machines have been upgraded). This is going to be a little more complicated, becausechances are, you’ve made a few changes to the stable branch as well, and it may not be possible toautomatically merge them all.To merge changes from the trunk back to your branch, use this:cd my_branch_dirsvn merge /path/to/repos/proj/trunkCheck for conflicts with svn status, resolve them if necessary, run any appropriate tests (forexample, config file syntax checkers) to check for conflicts, and then commit the changes as usual.To merge your branch back into the trunk, first check out a clean copy of the trunk. Then (from thatchecked-out directory), run this:svn merge --reintegrate /path/to/repos/proj/branch15Download 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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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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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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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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