HP LaserJet printer doesn't have 2 sided option

In addition to lamcro and wdypdx22's answer (check that the hplip package is installed) you need to make sure your printer is set to using the right driver. In System->Administration->Printers you can select the printer:

Right click on your printer and select properties, then click on the Button next to Make and Model that is labeled "Change", then the system will go looking for a driver:

Since you have it installed this won't take long (it can fetch updated ones from openprinting.org so there's never a need to manually install drivers). After the search it will give you an option to use the driver, select the one with (HPIJS). Now the printer options should be available in the "Printer Options" section of the last screenshot.

As a bonus, HP provides a native tool for Linux users that provides even more features than the bundled generic tool. It's called the hplip toolbox, you can install it by installing the hplip-gui package or just search for it in the Software Center.

This is the tool I prefer to use to manager my hp printers. There is a wishlist request bug asking that when anyone with an hp printer plugs in it just installs all this automagically, which would be pretty great.

In the output of lpoptions -l, you should see a line that says:

HPOption_Duplexer/Duplex Unit: True *False

You can change this to True via lpoptions -o HPOption_Duplexer=True, and then your print dialog should allow you to print double-sided.

If you don't even have the "HPOption_Duplexer" option (e.g., lpoptions -l | fgrep -c Duplexer prints 0), then:

1. either you have the incorrect printer description file configured (the so-called PPD),
2. or you didn't check the "Duplex printing" option in the printer capabilities section.

To solve 1., the quickest path is probably to re-install the printer and choose the correct make/model combination.

To address 2., just open System -> Administration -> Printers, right-click on your printer and choose "Properties", then click on "Installed options" in the left pane and finally check the "Duplex printing" box on the right.

I found a lot of help here: http://www.linuxfoundation.org/collaborate/workgroups/openprinting

Here's a link to your model: http://www.openprinting.org/printer/HP/HP-LaserJet_P2015

The site helped a lot with printer issues I was having a while back.