Computer Laboratory

Common printing problems

Hardware problems with the printers should be reported to [Javascript required]. If you have any document problems which are not addressed by the cases below, please contact [Javascript required]

Why does my file not print?

Make sure you have sent the file to the right printer.

Under Linux, this can happen if you set your PRINTER environment variable in the wrong place. Most people set it in the file .profile, but unfortunately, many popular window managers nowadays (such as kde or gnome) start up before reading the .profile file. Consequently, anything started by your window manager (for example as a menu item) doesn't know about the value you have assigned to PRINTER, and instead attempts to use the lab default printer, which is called aaa-dustbin. aaa-dustbin isn't a real printer, just a printer queue, so anything sent to aaa-dustbin stays in the queue until it is deleted or redirected.

To prevent that, set the PRINTER environment variable in a file called .xprofile in your home directory, as this will be read before your window manager starts up. Don't forget that you will also need an export PRINTER line for the PRINTER assignment to take effect.

Why do grey-scale PDF pages end up printed with CMY colour toner?

By default, the departmental CUPS server converts any PDF file sent to it first into PostScript, before passing it on to the printer. With the particular GhostScript version used (as of 2016/2017), this causes the colour encoding of grey areas to be converted in a way that causes the printer to switch to 4-colour print mode, even if the PDF page did not contain any colors other than black, grey and white. This not only causes pages involving grey-scale figures to appear more blurry than pages with only black and white. It also wastes more toner.

Workaround: Most of our printers now understand PDF directly. On Linux, bypass the GhostScript conversion step and send the PDF file directly to the printer using

$ lpr -l file.pdf

Solution: The departmental CUPS server needs updating to a more recent version that passes on PDF unharmed.

PDF files (Evince considered harmful)

Some PDFs might fail to print entirely or might produce printout with some fonts replaced by black areas. This problem is especially common with the evince utility, which is the default PDF viewer under most Linux distributions (sometimes known as "Document Viewer"). If you encounter this problem, try the following steps:

  • Print the document from a different utility, such as okular or Acroread.
  • Print the document from the command line (using lpr).
  • Save the output to file, which will create a PostScript file. You can then "clean it up" using ps2ps, which takes your file as input and outputs a version which conforms with the PostScript Document Structuring Conventions, then you should be able to print that output.

Avahi on Ubuntu 13 and higher

The avahi-daemon causes the gtk+ library on Ubuntu 13 (or newer) systems used by many GUIs (e.g. firefox and chrome) to overload the print spooler by opening hundreds of simultaneous connections, causing the GUI to crash. This causes a problem for everyone in the lab, not just Ubuntu users.

To avoid this, we are removing the avahi-daemon on all Ubuntu 14.04 systems. If you manage a machine which needs it, simply add ‘avahi-daemon’ to /etc/user-config/bundles as usual, and it will be auto-installed.

Printing on US Letter paper

The lab does not keep stocks of North American Letter paper (216 x 279 mm). It is available from some commercial printers in Cambridge but only if you use their printing facilities to print onto it.