Comment 3 for bug 1690380

If manually alter permissions (which isn't a persistent solution due to log rotation):

sudo chmod go+r /var/log/nagios3/nagios.log

Then can see things like this:

[2017-05-15 14:31:10] Nagios 3.5.1 starting... (PID=2141)

...here:

http://localhost/cgi-bin/nagios3/history.cgi?host=localhost&service=Current+Load

More usefully, you would be able to see when nagios checks fail etc. here too. I.e. this bug means it's only possible to see the current status using the nagios-cgi UI, not any history.