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Add the following to your rc.conf:

hpiod_enable="YES"
hpssd_enable="YES"

The default setup runs hpiod as the hplip user and adds 
hplip to the operator group.  So all you have to do if you
have a custom ruleset setup is add the following to that
ruleset in devfs.rules:

add path 'ugen*' group operator
add path 'ugen*' mode 0660

If you have never setup devfs.rules please read the
manpage and see:
http://am-productions.biz/docs/devfs.rules.php

The printer MUST attach as a ugen(4) device.  This means
that you must NOT have "device ulpt" in your kernel and
ulpt must NOT be loaded as a kernel module.

If you are seeing device connection errors restart the
printing chain with the following command.  NOTE: It MUST
be restarted in the stated order.
%%PREFIX%%/etc/rc.d/hpiod restart && \
%%PREFIX%%/etc/rc.d/hpssd restart && \
%%PREFIX%%/etc/rc.d/cupsd restart

If upgrading from version 0.9.11 add the following to
your %%PREFIX%%/etc/hp/hplip.conf:
[dirs]
run=/var/run
home=%%PREFIX%%/share/hplip
ppd=%%PREFIX%%/share/ppd

Or just copy the hplip.conf.sample config. [Recommended]
cp %%PREFIX%%/etc/hp/hplip.conf.sample \
   %%PREFIX%%/etc/hp/hplip.conf

If you are having problems check:
http://am-productions.biz/docs/hplip.php
If you still having problems send the relevant part of
your /var/log/messages, console output from the hp-*
utility that you are trying to run, and your rc.conf +
devfs.rules files to the maintainer.
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