Nagios

Change default start page

Edit /usr/share/nagios3/htdocs/index.html and change:

<FRAME SRC="main.html" NAME="main">

to

<FRAME SRC="/cgi-bin/nagios3/status.cgi?host=all" NAME="main">

Enabling external commands

From /usr/share/doc/nagios3-common/README.Debian:

Nagios 3 is not configured to look for external commands in the
default configuration as a security feature. To enable external
commands, you need to allow the web server write access to the
nagios command pipe.  the simplest way of doing this is to
set check_external_commands=1 in your nagios configuration,
and then change the permissions in a way which will be maintained
across package upgrades (otherwise dpkg will overwrite your
permission changes).  The following is the recommended approach:

- activate external command checks in the nagios configuration. this
  can be done by setting check_external_commands=1 in the file
  /etc/nagios3/nagios.cfg.

- perform the following commands to change directory permissions and
  to make the changes permanent:

/etc/init.d/nagios3 stop
dpkg-statoverride --update --add nagios www-data 2710 /var/lib/nagios3/rw
dpkg-statoverride --update --add nagios nagios 751 /var/lib/nagios3
/etc/init.d/nagios3 start

Creating a MySQL user for monitoring

Locally:

GRANT USAGE ON *.* TO 'nagios'@'localhost'

Remotely:

GRANT USAGE ON *.* TO 'nagios'@'%'