When upgrading a Debian 8 system I encountered the following error:
Setting up procps (2:3.3.9-9+deb8u1) ... Job for systemd-sysctl.service failed. See 'systemctl status systemd-sysctl.service' and 'journalctl -xn' for details. invoke-rc.d: initscript procps, action "start" failed. dpkg: error processing package procps (--configure): subprocess installed post-installation script returned error exit status 1 Errors were encountered while processing: procps E: Sub-process /usr/bin/dpkg returned an error code (1)
sysctl loads its own file from /etc/sysctl.d and additional ones from /usr/lib/sysctl.d. I checked these files and found an error in a variable that the kernel would not allow to be set during virtual machine restrictions. I changed the line and the updates worked again.