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Nagios, 2nd Edition

Cover of Nagios, 2nd Edition by Wolfgang Barth Published by No Starch Press
  1. Nagios: System and Network Monitoring, 2nd Edition
    1. Foreword to the second edition
      1. What's New in the Second Edition?
      2. Information Sources on the Internet
    2. Introduction
      1. The tests
      2. The suppliers of information
      3. Keeping admins up-to-date
      4. Taking in information from outside
      5. Other tools for network monitoring
      6. About This Book
      7. Further notes on the book
      8. Note of Thanks
    3. I. From Source Code to a Running Installation
      1. 1. Installation
      2. 2. Nagios Configuration
      3. 3. Startup
    4. II. In More Detail...
      1. 4. Nagios Basics
      2. 5. Service Checks and How They Are Performed
      3. 6. Plugins for Network Services
      4. 7. Testing Local Resources
      5. 8. Plugins for Special Tasks
      6. 9. Executing Plugins via SSH
      7. 10. The Nagios Remote Plugin Executor (NRPE)
      8. 11. Collecting Information Relevant for Monitoring with SNMP
      9. 12. The Nagios Notification System
      10. 13. Passive Tests with the External Command File
      11. 14. The Nagios Service Check Acceptor (NSCA)
      12. 15. Distributed Monitoring
    5. III. The Web Interface and Other Ways to Visualize Nagios Data
      1. 16. The Classical Web Interface
      2. 17. Flexible Web Interface with the NDOUtils
      3. 18. NagVis
      4. 19. Graphic Display of Performance Data
    6. IV. Part IV Special Applications
      1. 20. Monitoring Windows Servers
      2. 21. Monitoring Room Temperature and Humidity
      3. 22. Monitoring SAP Systems
      4. 23. Processing Events with the EventDB
    7. V. Part V Development
      1. 24. Writing Your Own Plugins
      2. 25. Determining File and Directory Sizes
      3. 26. Monitoring Oracle with the Instant Client
    8. VI. Part VI Appendixes
      1. A. An Overview of the Nagios Configuration Parameters
      2. B. Rapidly Alternating States: Flapping
      3. C. Event Handlers
      4. D. Macros
      5. E. Single Sign-On for the Nagios Web Interface
      6. F. Tips on Optimizing Performance
      7. G. The Embedded Perl Interpreter
      8. H. What's New in Nagios 3.0?
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Chapter 25. Determining File and Directory Sizes

For a specific example of a Perl plugin, we will look at check_du.pl.[296] It is used to determine the size of specified files or directories and to check whether the total size lies within preset thresholds. To do this, it calls the system program du:

user@linux:~$ du -cs /var/spool/var/log
26524   /var/spool
745640  /var/log
772164  total

When used with the -s option, du does not list all the individual subdirectories but just shows the total size. -c adds up individual values to reach a total size.

At the beginning, the plugin generates a new new Nagios::Plugin object with the new constructor so that it can make use of the functions of the module:

#!/usr/bin/perl -w use strict; use warnings; use FindBin; ...

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