Empty Graphs in Cacti - on ubuntu

[gandalf]

Even this should not happen. cactiuser needs permissions to create, write and read (new) rrd files in the ./rra directory. The httpd user only needs read access to the files.
New files are created by the poller, run from crontab. If you use cactiuser with crontab, all should be fine (ok, you may have a look at the umask of this user).
Of course, if you manually run the poller as root (as I did often, at least "in the beginning"), you later have to chown/chmod the files that may be owned by root. But apart from that, manual intervention should not be necessary
Reinhard