Linux System Administration Recipes A Problem-Solution Approach

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CHAPTER 3 ■ MONITORING AND UPDATINGdefine service {hostgroup_nameservice_descriptioncheck_commanduse}nrpeSMTPcheck_nrpe_1arg!check_smtpgeneric-serviceThen set up which hosts have these checks by defining a hostgroup in conf.d/hostgroups_nagios2.cfg:define hostgroup {hostgroup_name disk-localaliasHosts with /localmembers client1, client2}define hostgroup {hostgroup_name smtpaliasHosts with SMTPmembers client1, client2, server1}Restart Nagios, and you’re done!■ Note One gotcha to watch out for is that the check_disk command takes percentage arguments, and it warnson percentage free, rather than percentage used. Mine is set to warn at 10 percent and to be critical at 5 percent.3-9. Enabling External Commands in NagiosEnabling external commands means that you can do various things from the web interface, such asrestarting services. To turn them on, first you need to stop Nagios (/etc/init.d/nagios3 stop). Editnagios.cfg, and set the check_external_commands value to 1.Next, if you’re using Debian, you need to set the permissions on /var/lib/nagios2/rw correctly. Tomake that directory read-writeable by your apache2 user (on Debian this is www-data), use thesecommands:dpkg-statoverride --update --add nagios www-data 2710 /var/lib/nagios2/rwdpkg-statoverride --update --add nagios nagios 751 /var/lib/nagios2This will override the package defaults to set the rw directory to be owned by the www-data group andto be group-executable. It also sets the setgid bit so that files created within this directory will also beowned by www-data rather than by the user who created the file. The permissions on the parent directory(/var/lib/nagios2) are changed similarly, but by using the nagios group rather than www-data andwithout the setgid bit.76Download at WoweBook.Com
CHAPTER 3 ■ MONITORING AND UPDATINGNow restart Nagios (/etc/init.d/nagios3 start), and you should be able to use commands. Testthis by clicking the Service Detail link in the sidebar, and then pick one of the services. Figure 3-2 showsthe screen for the HTTP service on localhost; the commands are in the box on the right of the screen. Aneasy test is to click “Re-schedule the next check of this service.” You’ll be given the opportunity to set thetime for the next check.Figure 3-2. State information for the HTTP service on localhost. Note the external commands in the boxat right.It’s also useful with external commands to be able to temporarily turn off checks or notifications of aservice or host (for example, if you are aware that it’s down and don’t want to keep being told!).You can also restart Nagios itself from the web interface (using the Process Info page) if you’relogged in as nagiosadmin. To restart it as any other user, you’ll need to edit /etc/nagios3/cgi.cfg to addthe username to the authorized_for_system_commands line.■ Note You can find a list of all available external commands at http://www.nagios.org/developerinfo/externalcommands/commandlist.php.77Download at WoweBook.Com
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Contents■About the Author .......
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■ CONTENTS3-7. Writing a Nagios P
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■ CONTENTS■Chapter 8: Using the
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■ CONTENTSAbout the Author■Juli
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■ CONTENTSAcknowledgmentsMany tha
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■ CONTENTSIntroductionThis book i
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■ INTRODUCTIONDownloading the Cod
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C H A P T E R 1■ ■ ■Saving Yo
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CHAPTER 1 ■ SAVING YOURSELF EFFOR
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C H A P T E R 2■ ■ ■Centraliz
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CHAPTER 2 ■ CENTRALIZING YOUR NET
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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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C H A P T E R 7■ ■ ■Working w
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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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C H A P T E R 9■ ■ ■Working w
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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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