Comment 31 for bug 416513

This affects me too, with an HP Officejet j6400, duplexer unit is installed.

Like Gustav Svensson, duplex printing works correctly when using:

lpr -o sides=two-sided-long-edge

, but his suggested fix of editing the PPD file has not worked for me.

Running Ubuntu 12.04, hplip version 3.12.6.

The "Duplexer Installed" option is set to yes, but greyed out in the HP Device manager. When attempting to print, there's no "two-sided" option available in the print dialog, and an exclamation mark appears with the text "Some of the settings in the dialog conflict." This disappears when selecting "One sided printing" from the "layout" drop-down. The "Advanced" tab of the print dialog has a checked box next to "Duplexer installed"

As with a few of the other commenters, this used to work correctly, many versions of hplip ago