For the audience, to reproduce this easily: Change /etc/udev/rules.d/20-names.rules as follows:
replace #BUS=="usb", KERNEL=="lp[0-9]*", NAME="usb%k" with BUS=="usb", KERNEL=="lp[0-9]*", NAME="usblp1" . -- USB driver cannot find printers if usblp0 is disconnected https://launchpad.net/bugs/64725 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
