I'm running Observium in a Freebsd-10, no problems here.
# /etc/crontab - root's crontab for FreeBSD
#
# $FreeBSD: releng/10.3/etc/crontab 194170 2009-06-14 06:37:19Z brian $
#
SHELL=/bin/sh
PATH=/etc:/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin
#
#minute hour mday month wday who command
#
# Observium - poller
33 */6 * * * root /opt/observium/discovery.php -h all > /dev/null 2>&1
*/5 * * * * root /opt/observium/discovery.php -h new > /dev/null 2>&1
*/5 * * * * root /opt/observium/poller-wrapper.py 16 > /dev/null 2>&1
#
# Observium - billing
*/5 * * * * root /opt/observium/poll-billing.php > /dev/null 2>&1
01 * * * * root /opt/observium/billing-calculate.php > /dev/null 2>&1
Permissions on rrd folder:
# ls -la | grep rrd
drwxr-xr-x 58 root www 2048 Oct 18 20:10 rrd
You can output poller to a file, for debug purposes (on your crontab file):
#*/5 * * * * root /opt/observium/poller-wrapper.py 16 > /opt/observium/logs/poller.log
Regards,