Linux System Administration Recipes A Problem-Solution Approach

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CHAPTER 3 ■ MONITORING AND UPDATING# this command runs a program $ARG1$ with one argument, $ARG2$, passed to $ARG1$define command {command_name check_nrpecommand_line /usr/lib/nagios/plugins/check_nrpe -H $HOSTADDRESS$ -c $ ARG1$ -a $ARG2$}# this command runs a program $ARG1$ without any argument passed in to itdefine command {}command_namecommand_linecheck_nrpe_1arg/usr/lib/nagios/plugins/check_nrpe -H $HOSTADDRESS$ -c $ ARG1$Edit /etc/nagios/conf.d/services_nagios3.cfg on the monitored machine (cepheus in thisexample) to add the services you want to monitor:# SMTP doesn't need any arguments passed into the check_smtp# program, so we use check_nrpe_1argdefine service {service_description SMTPusegeneric-servicehostgroup_namenrpecheck_commandcheck_nrpe_1arg!check_smtp}define service {service_descriptionusehostgroup_namecheck_command}LOADgeneric-servicenrpecheck_nrpe_1arg!check_load# check_disk takes an argument, /, so we use check_nrpedefine service {service_description DISKusegeneric-servicehostgroup_namenrpecheck_commandcheck_nrpe!check_disk!/}■ Note This requires an nrpe hostgroup to be set up on the server.Commands that take only one argument—the service to check—use the check_nrpe_1arg command(see /etc/nagios-plugins/config/check_nrpe.cfg).If you want to give further arguments to commands, you need to edit /etc/nagios/nrpe.cfg on theclient machine so that the dont_blame_nrpe keyword has the value 1. Then use the check_nrpe command.In the previous code, I use it to pass the disk mount point to be checked.74Download at WoweBook.Com
CHAPTER 3 ■ MONITORING AND UPDATING■ Note Setting dont_blame_nrpe to 1 is a security hole. The arguments passed to NRPE aren’t thoroughlychecked/sanitized, so it is possible for an attacker to run arbitrary evil commands via the check_nrpe command.It’s up to you how you assess risk in your own setup and with the specific command that you’re using. You shouldcertainly at least understand what the command you’re passing in to check_nrpe will do with the options youprovide. In the previous example, check_nrpe!check_disk will just run the check_disk command without anyarguments on the monitored machine, with whatever disk is hard-coded in that command to be checked.check_nrpe!check_disk!/ will pass the third argument (here /) to check_disk, and check_disk will operate onthat argument. If your check_disk command involved, say, an echo line, and the argument was, instead of a diskmount point, some malicious code, then the malicious code could be echoed and thus run.Restart Nagios, and you should be able to start seeing information from your monitored machine.■ Note Instead of editing /etc/nagios/nrpe.cfg on the monitored machine, you can instead edit/etc/nagios/nrpe-local.cfg. NRPE will check both files (/etc/nagios/nrpe.cfg and /etc/nagios/nrpe-local.cfg), but if there is a conflict, /etc/nagios/nrpe-local.cfg will win. This has the advantageof keeping your local changes separate from the package files, so if the package is updated, there’s no risk ofyour changes being overwritten. Similarly, you can keep files in /etc/nagios/nrpe.d/.Possible commands are at /usr/lib/nagios/plugins on the client—or you can create your own in/etc/nagios/nrpe-local.cfg. Try these commands, added to /etc/nagios/nrpe-local.cfg:command[check_disk]=/usr/lib/nagios/plugins/check_disk -w 10% -c 5% -p $ARG1$command[check_smtp]=/usr/lib/nagios/plugins/check_smtp -w 1 -c 2The first one means that I can check whichever local disk I want, rather than being restricted to / aswith the default check_disk command; the second checks that SMTP is OK. Use them by adding thissection to conf.d/services-nagios2.cfg:define service {usehostgroup_nameservice_descriptioncheck_command}generic-servicedisk-localDISK-LOCAL2check_nrpe!check_disk!/local75Download 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 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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Linux System Administration Recipes A Problem-Solution Approach

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