I apologize for all these apt-related questions. I have rtfm'd on this ad nauseam. For years, literally.
Still, I'm routinely rendered utterly helpless by this sort of thing: % sudo apt-get -qq update % sudo apt-get -qq upgrade % sudo apt-get -qq dist-upgrade % sudo apt-get install ffmpeg Reading package lists... Done Building dependency tree Reading state information... Done Some packages could not be installed. This may mean that you have requested an impossible situation or if you are using the unstable distribution that some required packages have not yet been created or been moved out of Incoming. The following information may help to resolve the situation: The following packages have unmet dependencies: ffmpeg : Depends: libavcodec-ffmpeg56 (>= 7:2.7) but it is not going to be installed or libavcodec-ffmpeg-extra56 (>= 7:2.7) but it is not going to be installed Depends: libavdevice-ffmpeg56 (>= 7:2.6) but it is not going to be installed Depends: libavfilter-ffmpeg5 (>= 7:2.4) but it is not going to be installed Depends: libavformat-ffmpeg56 (>= 7:2.6) but it is not going to be installed E: Unable to correct problems, you have held broken packages. Where does one begin troubleshooting out such problems? Thanks in advance for any help. kj PS: # /etc/apt/apt.conf APT::Default-Release "jessie"; # /etc/apt/preferences Package: /^r-/ Pin: release n=stretch Pin-Priority: 995 # /etc/apt/sources.list deb http://http.us.debian.org/debian jessie main contrib non-free deb http://http.us.debian.org/debian jessie-updates main contrib deb http://security.debian.org jessie/updates main contrib non-free deb-src http://http.us.debian.org/debian jessie main contrib deb-src http://http.us.debian.org/debian jessie-updates main contrib deb-src http://security.debian.org jessie/updates main contrib non-free deb http://http.us.debian.org/debian stretch main contrib non-free deb-src http://http.us.debian.org/debian stretch main contrib deb http://download.videolan.org/pub/debian/stable / # needed for libdvdcss2 (see http://www.videolan.org/developers/libdvdcss.html) I have made no changes to my /etc/apt/apt.conf.d/, /etc/apt/preferences.d, and /etc/apt/sources.list.d/ that I'm aware of. The last two of these directories are empty. The first one contains % ls -l /etc/apt/apt.conf.d -rw-rw-r-- 1 root root 82 Nov 22 13:45 00CDMountPoint -rw-rw-r-- 1 root root 40 Nov 22 13:45 00trustcdrom -rw-rw-r-- 1 root root 643 Nov 22 13:45 01autoremove -rw-r--r-- 1 root root 981 Dec 19 09:44 01autoremove-kernels -rw-rw-r-- 1 root root 243 Nov 22 13:45 20dbus -rw-rw-r-- 1 root root 141 Nov 22 13:45 20listchanges -rw-rw-r-- 1 root root 1040 Nov 22 13:45 20packagekit -rw-rw-r-- 1 root root 3945 Nov 22 13:45 50unattended-upgrades -rw-rw-r-- 1 root root 182 Nov 22 13:45 70debconf