# apt-get install libssl-dev 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: libssl-dev : Depends: libssl1.0.0 (= 1.0.1t-1+deb8u6) but 1.0.2k-1~bpo8+1 is to be installed Recommends: libssl-doc but it is not going to be installed E: Unable to correct problems, you have held broken packages.
# apt-cache policy libssl-dev libssl-dev: Installed: (none) Candidate: 1.0.1t-1+deb8u6 Version table: 1.0.2k-1~bpo8+1 0 400 http://httpredir.debian.org/debian/ jessie-backports/main amd64 Packages 1.0.1t-1+deb8u6 0 900 http://security.debian.org/ jessie/updates/main amd64 Packages 1.0.1t-1+deb8u5 0 900 http://httpredir.debian.org/debian/ jessie/main amd64 Packages
100 <= P < 500 causes a version to be installed unless there is a version available belonging to some other distribution or the installed version is more recent
500 <= P < 990 causes a version to be installed unless there is a version available belonging to the target release or the installed version is more recent
# lsb_release -a No LSB modules are available. Distributor ID: Debian Description: Debian GNU/Linux 8.7 (jessie) Release: 8.7 Codename: jessie # cat /etc/apt/preferences Package: * Pin: release a=stable Pin-Priority: 900 Package: * Pin: release a=jessie-backports Pin-Priority: 400
It seems that my priorities are pinned correctly, notwithstanding
apt-get is trying to install version from the
# apt-cache policy libssl1.0.0 libssl1.0.0: Installed: 1.0.2k-1~bpo8+1 Candidate: 1.0.2k-1~bpo8+1 Version table: *** 1.0.2k-1~bpo8+1 0 100 /var/lib/dpkg/status 1.0.1t-1+deb8u6 0 990 http://security.debian.org/ jessie/updates/main amd64 Packages 1.0.1t-1+deb8u5 0 990 http://httpredir.debian.org/debian/ jessie/main amd64 Packages
I think I now understand what is the problem.