I've been working in Debian for years, professionally for the last 8+ years, so I too was frustrated and not understanding why this was the case that 'aptitude' wasn't giving the files on this Sid system. I had to use 'apt-file search cupsd.conf' to verify I was installing the correct packages, but still no fix — 'aptitude' wasn't doing what I expected.
> It is the postinst of cups-daemon which arranges for cupsd.conf to be
> written to /etc/cups
Yes, and the postinst kept failing due to the cupds.conf file being missing. I no longer have the specific message and printing is a lot of work to re-set-up every time Cups decides to break my printing (which is often), and I understand that the Sid/Unstable branch shouldn't be used in mission-critical setups, but this is my desktop so I'm ok with some breakages. I've not reported bugs against cups because breaking things seems to be the norm. But against Aptitude, I figured that would be wanted to be known. I don't have the time or my wife the energy for me to uninstall and reinstall and reconfigure printers.
Cups packages, per the request, are:
"
root@bigboi:~# dpkg -l | grep cups
ii cups 1.6.2-10 amd64 Common UNIX Printing System(tm) - server
ii cups-browsed 1.0.34-3 amd64 OpenPrinting CUPS Filters - cups-browsed
ii cups-bsd 1.6.2-10 amd64 Common UNIX Printing System(tm) - BSD commands
ii cups-client 1.6.2-10 amd64 Common UNIX Printing System(tm) - client programs (SysV)
ii cups-common 1.6.2-10 all Common UNIX Printing System(tm) - common files
ii cups-daemon 1.6.2-10 amd64 Common UNIX Printing System(tm) - daemon
ii cups-filters 1.0.34-3 amd64 OpenPrinting CUPS Filters
ii cups-pk-helper 0.2.3-3 amd64 PolicyKit helper to configure cups with fine-grained privileges
ii cups-ppdc 1.5.3-2.15 amd64 Common UNIX Printing System(tm) - PPD manipulation utilities
ii cups-server-common 1.6.2-10 all Common UNIX Printing System(tm) - server common files
ii ghostscript-cups 9.05~dfsg-6.3 amd64 interpreter for the PostScript language and for PDF - CUPS filters
ii hplip-cups 3.13.4-1 all transitional dummy package for hpcups printer driver
ii libcups2:amd64 1.6.2-10 amd64 Common UNIX Printing System(tm) - Core library
ii libcupscgi1:amd64 1.6.2-10 amd64 Common UNIX Printing System(tm) - CGI library
rc libcupsdriver1:amd64 1.5.3-2.15 amd64 Common UNIX Printing System(tm) - Driver library
ii libcupsfilters1:amd64 1.0.18-2.1 amd64 OpenPrinting CUPS Filters - Shared library
ii libcupsimage2:amd64 1.6.2-10 amd64 Common UNIX Printing System(tm) - Raster image library
ii libcupsmime1:amd64 1.6.2-10 amd64 Common UNIX Printing System(tm) - MIME library
ii libcupsppdc1:amd64 1.6.2-10 amd64 Common UNIX Printing System(tm) - PPD manipulation library
ii printer-driver-hpcups 3.13.4-1+b1 amd64 HP Linux Printing and Imaging - CUPS Raster driver (hpcups)
ii python-cups 1.9.48-1.1 amd64 Python bindings for CUPS
ii python-cupshelpers 1.3.7-4 all Python utility modules around the CUPS printing system
"