iiab/roles/cups

CUPS Printing README

CUPS (also known as the "Common UNIX Printing System") is the standards-based, open source printing system for Linux and macOS.

It allows your Internet-in-a-Box (IIAB) to act as a print server.

This can be useful if a printer is attached to your IIAB — so student/teacher print jobs from client computers and phones can be processed — and then sent to the appropriate printer.

Web Administration

Please administer CUPS at http://box/print using:

• Username: Admin
• Password: changeme

Or use any Linux user that is a member of the Linux group: lpadmin

Security

The above uses 'SystemGroup lpadmin' in /etc/cups/cups-files.conf — in coordination with about 15 '@SYSTEM' lines and 'DefaultAuthType Basic' in /etc/cups/cupsd.conf

CUPS creates a 10-year (unsigned) https certificate during installation, that will be very confusing to non-technical users when they log in, as a result of modern browser warnings.

How it Works

http://localhost:631 can be useful if NGINX redirects or CUPS permissions are set wrong.

Beware that http://box:631 and http://box.lan:631 will not work, due to a known issue with CUPS since 2009.

Understand how IIAB configures CUPS for all IP addresses and all hostnames (despite the above CUPS problem!) by reading these in-line explanations:

• /opt/iiab/iiab/roles/cups/tasks/install.yml

Modify these 2 files at your own risk:

• /etc/cups/cupsd.conf (run sudo cupsctl and sudo cupsd -t to verify the file!)
• /etc/nginx/conf.d/cups.conf

If you make modifications to the above files, don't forget to restart systemd services:

systemctl restart cups cups-browsed nginx

Docs and Updates

• https://www.cups.org/documentation.html
  • https://github.com/apple/cups/releases
• https://openprinting.github.io/cups/
  • https://github.com/OpenPrinting/cups/releases/