DevOps Classroom Series – 24/June/2021

Configuring Nagios object definitions

Understanding how checks work

  • Nagios requires all plugins to follow a specific, easy to follow behaviour
  • Nagios relies on exit codes of the Nagios plugins
Exit code Status Description
0 OK Working correctly
1 WARNING Working but needs attention
2 CRITICAL Not working or requires attention
3 UNKNOWN Plugin was unable to determine the status of host or service
  • Standard output from command is not parsed by Nagios and is usually formatted in the following way
PLUGIN STATUS - status description
  • Nagios plugins use options for their configuration

    • -h, –help: This provides help
    • -V, –version: This prints the version
    • -v , –verbose: This prints the detailed information on what plugin is doing
    • -t , –timeout
    • -w, –warning
    • -c, –critical
    • -H, –hostname
    • -4, –use-ipv4
    • -6, –use-ipv6
  • All the network related plugins have the following standard option

    • -p, –port
    • -w, –warning
    • -c, –critical
    • -s, –send: This provides the string that will be sent to server
    • -e, –expect: This provides the string that should be sent back from server
    • -q, –quit: This provides the string to be sent to close the connection
    • -S, –ssl
    • -D, –certificate

Testing the connection to remote host

  • For this we have check_ping plugin Refer Here for official documentation
  • Creating the command for the host-alive
define command {
    command_name   check-host-alive
    command_line   $USER1$/check_ping -H $HOSTADDRESS$ -w 2000,50% -c 5000,60% -p 5

Testing the connectivity using TCP and UDP

Testing the websites

  • Refer Here for the official documentation of check_http plugin

Testing the databases

Area of concern

  • If we need to alert/notify the user on some details such as
    • free disk space
    • process
    • CPU stress

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