Nagios3 on Debian
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Installation was a breeze, like usual on debian, just:
apt-get install nagios3
Lots of dependencies, a quick question about Samba, then I did this:
cd /etc/nagios3 htpasswd -c htpasswd.users nagiosadmin
Then I was able to login via the web interface, nice! And another nice surprise - they added the default gateway as a bonus. Cool!