Bug#606930: apt CDROM method fails if more than one package is required from a CDROM

I think I'm still hitting this issue 10 years later. On Ubuntu 18.04.1 I was trying to add the 18.04.2 CD as a source to upgrade from. It would seem to work and I could upgrade single packages, but if I would do an upgrade I would get "File not found" for every package even though the paths being referenced were correct. The "cdrom://" protocol being sort of obtuse really made debugging it difficult. I randomly noticed in my output from "apt-config dump": Acquire::cdrom::mount "/media/cdrom/"; even though apt-cdrom automatically mounted the disk to "/media/apt". I decided to try symlinking "/media/cdrom" to "/media/apt" and it started working properly!

So it appears that there's some disconnect in apt between "/media/apt" and "/media/cdrom" and when to look at each, or "Acquire::cdrom::mount" is not getting updated when apt-cdrom is being ran. A similar issue was posted here - https://www.linuxquestions.org/questions/debian-26/problems-with-apt-cdrom-add-command-866761/

Hope this helps.

-Jesse