This will still fail if a package upgrade prompts for a change to a configuration file. You can force it to keep existing files and therefore not ask. The comma

This will still fail if a package upgrade prompts for a change to a configuration file. You can force it to keep existing files and therefore not ask. The command I use is: DEBIAN_FRONTEND=noninteractive apt-get -y -o Dpkg::Options::="--force-confdef" -o Dpkg::Options::="--force-confold" install blah wibble (This also works for "upgrade" as well as "install".)