lpoptions cannot change system-wide default printer

[Niklas Rother]

According to "man lpoptions":

> When run by the root user, lpoptions gets and sets default options and
> instances for all users in the /etc/cups/lpoptions file. Otherwise,
> the per-user defaults are managed in the ~/.cups/lpoptions file.

According to my experimentation, this is incorrect. When lpoptions is run as root, the file "/root/.cups/lpoptions" is updated (aka the personal default printer of root), not "/etc/cups/lpoptions" (aka the system-wide default printer).

I'm unsure whether this is a documentation bug or wrong behavior. I assume the later, because there seems to be no other option to set the system-wide default printer.

root@mi553-022:~# lsb_release -rd
Description: Ubuntu 20.04.3 LTS
Release: 20.04
root@mi553-022:~# apt-cache policy cups
cups:
  Installed: 2.3.1-9ubuntu1.1
  Candidate: 2.3.1-9ubuntu1.1
  Version table:
 *** 2.3.1-9ubuntu1.1 500
        500 http://ftp.luis.uni-hannover.de/ubuntu focal-updates/main amd64 Packages
        500 http://ftp.luis.uni-hannover.de/ubuntu focal-security/main amd64 Packages
        100 /var/lib/dpkg/status
     2.3.1-9ubuntu1 500
        500 http://ftp.luis.uni-hannover.de/ubuntu focal/main amd64 Packages
     2.2.7-1ubuntu2.8 500
        500 http://ftp.luis.uni-hannover.de/ubuntu bionic-security/main amd64 Packages