Nagios Notes

Get Nagios at http://www.nagios.org. You'll need both the base nagios package as well as nagios-plugins. On 9-17-2006, I got nagios-2.5-1.el4.rf.i386.rpm and nagios-plugins-1.4.2-1.2.el4.rf.i386.rpm.

A rpm -qip nagios-plugins-1.4.2-1.2.el4.rf.i386.rpm command said

... you may need additional packages. Depending on what plugins you
use, the following packages may be required:

    bind-utils, mysql, net-snmp-utils, ntp, openldap,
    openssh-clients, openssl, postgresql-libs
    qstat, radiusclient, samba-client, sendmail

Nagios installed cleanly, but nagios-plugins required all these pre-reqs

• fping-2.4-1.b2.2.el4.rf.i386.rpm
• perl-Socket6-0.19-1.2.el4.rf.i386.rpm
• perl-Crypt-DES-2.05-3.2.el4.rf.i386.rpm
• perl-Net-SNMP-5.2.0-1.2.el4.rf.noarch.rpm

• I did not for example, have to add 'Include /usr/local/nagios/etc/nagios-server.conf’ to the bottom of the /etc/httpd/conf/httpd.conf file because there already was an Include conf.d/*.conf in the httpd.conf file and there was a nagios.conf file in that /etc/httpd/conf.d directory, identical to /usr/local/nagios/etc/nagios-server.conf.
• Where this web page mentions /usr/local/nagios/sbin, I have /usr/lib/nagios/cgi.
• Where this web page mentions /usr/local/nagios/share, I have /usr/share/nagios.
• Where this web page mentions /usr/local/nagios/etc/htpasswd.users, I have /etc/nagios/htpasswd.users.
• I didn't have to rename cgi.cfg-sample to cgi.cfg, which was in the /etc/nagios directory by the way.
• I did not create a file named /usr/lib/nagios/cgi/.htaccess with these lines

     AuthName "Nagios Access"
     AuthType Basic
     AuthUserFile /usr/local/nagios/etc/htpasswd.users
     require valid-user
  

  I don't think I have to do this, but I'm not certain.

I added a nagiosadmin id to my /etc/nagios/htpasswd.users file.

   htpasswd -c  /etc/nagios/htpasswd.users nagiosadmin
   New password: global
   Re-type new password: global
Adding password for user nagiosadmin

I had to go through /etc/nagios/cgi.cfg file and change and/or un-comment the following lines:

   authorized_for_system_information=nagiosadmin
   authorized_for_configuration_information=nagiosadmin
   authorized_for_system_commands=nagiosadmin
   authorized_for_all_services=nagiosadmin
   authorized_for_all_hosts=nagiosadmin
   authorized_for_all_service_commands=nagiosadmin
   authorized_for_all_host_commands=nagiosadmin

I updated /etc/nagios/minimal.cfg to

• Deleted the 6 duplicate command_name definitions (check-host-alive, check_ping, check_local_disk, check_local_users, check_local_procs, check_local_load) that are already in the checkcommands.cfg file.
• Commented the notify-by-email & host-notify-by-email command stanzas. They're already in /etc/nagios/misccommands.cfg.
• put in my e-mail address instead of nagios-admin@localhost.
• Change the hostname of their one sample host from localhost to linux2.
• Added a second host named HPpc at 192.168.1.3 for my web server PC.
• Added a third host named linux3 and defined some services for Nagios to monitor on it.

NRPE - Nagios Remote Plug-in Executor

I downloaded 2.0, did the typical

   zip -d < nrpe-2.0.tar.gz | tar xvf -
   cd nrpe-2.0
   ./configure
   make all

   *** Compile finished ***

   If the NRPE daemon and client compiled without any errors, you
   can continue with installation.  The NRPE daemon and client
   binaries are located in the src/ subdirectory.

    ** If this is your monitoring host **

        - Copy the check_nrpe client to the directory that
          contains your Nagios plugins.
        - Create a command definition in your Nagios config
          file for the NRPE client.  See the README file for
          more info on doing this.

    ** If this host will be running the NRPE daemon **

        - Copy the nrpe daemon to /usr/sbin, /usr/local/nagios
          or wherever you feel it fits best.
        - Copy the sample nrpe.cfg config file to /etc,
          /usr/local/nagios or wherever you feel it fits best.
        - Modify the /etc/services file and configure NRPE to
          run under inetd, xinetd, or as a standalone daemon.
          See the README file for more info on doing this.

Configuring Nagios Monitor Machine

On linux2, my Nagios server,

• cp -p src/check_nrpe /usr/lib/nagios/plugins
• vi /etc/nagios/minimal.cfg and I added these lines,

     # This is for NRPE   (RAJ)
     define command{
        command_name    check_nrpe
        command_line    /usr/lib/nagios/plugins/check_nrpe -H $HOSTADDRESS$ \
           -c $ARG1$ -a $ARG2$ $ARG3$ $ARG4$
     }
  

• vi /etc/services

  and added this line
     nrpe            5666/tcp        # NRPE - Nagios Remote Plug-in Executor
  

• I need to prefix any check_command line in a define service stanza, with

     check_command  check_nrpe!yourcommand-in-the-nrpe.cfg-file-on-the-remote-host
  

Configuring each Nagios Client Machine

On each Linux client machine,

   scp -p root@linux2:nrpe-2.0/src/nrpe /usr/bin
   scp -p root@linux2:nrpe-2.0/nrpe.cfg /etc
   adduser -u 401 nagios
   vi /etc/xinetd.d/nrpe

   # description: NRPE (Nagios Remote Plug-in Executor)
   service nrpe
   {
     flags           = REUSE
     socket_type     = stream
     wait            = no
     user            = nagios
     server          = /usr/bin/nrpe
     server_args     = -c /etc/nrpe.cfg --inetd
     log_on_failure  += USERID
     disable         = no
     only_from       = 192.168.1.222
   }

To install the Nagios plug-ins, on each remote host,

   mkdir /mnt/linux
   mount linux2:/home/linux /mnt/linux
   cd /mnt/linux/extras/
   rpm -Uvh nagios-plugins-1.4.2-1.2.el4.rf.i386.rpm  \
            perl-Net-SNMP-5.2.0-1.2.el4.rf.noarch.rpm \
            fping-2.4-1.b2.2.el4.rf.i386.rpm          \
            perl-Crypt-DES-2.05-3.2.el4.rf.i386.rpm   \
            perl-Socket6-0.19-1.2.el4.rf.i386.rpm
   cd
   umount /mnt/linux

   vi /etc/services
and added this line
   nrpe            5666/tcp        # NRPE - Nagios Remote Plug-in Executor

   service xinetd reload

Using Nagios