When I recently did my usual system update for the stable version Ubuntu GNOME, there were some updates pertaining to apt and the process failed when I executed the following command:
sudo apt-get upgrade
Usefully, some messages were issued and here’s a flavour:
Setting up apt (0.9.9.1~ubuntu3.1) …
ERROR: Can’t find the archive-keyring
Is the ubuntu-keyring package installed?
dpkg: error processing apt (--configure):
subprocess installed post-installation script returned error exit status 1
Errors were encountered while processing:
E: Sub-process /usr/bin/dpkg returned an error code (1)
Some searching on the web revealed that the problem was that there were no files in /usr/share/keyring when there should have been and I had not removed them myself so I have no idea how they disappeared. Various remedies were tried and any that needed software installed were non-starters because apt was disabled by the lack of keyring files. The workaround that restored things for me was to take a copy of the files in /usr/share/keyring from an Ubuntu GNOME 14.04 installation in a VirtualBox VM and copy them in to the same location in its Ubuntu GNOME 13.10 host. For those without such resources, I have packaged them in a zip file below. Other remedies like Y PPA also were suggested where I was reading but that software package needed installing beforehand so it was little use to me when the likes of Synaptic were disabled. If there are other remedies that do not involve an operating system re-installation, I would like to know about them too as well as possible causes for the file loss in the first place and how to avoid these.