Ok, I see what's happening here. The reason artful doesn't prompt is because /etc/localtime is prepopulated within the image:
$ tar tvf ubuntu-artful-core-cloudimg-amd64-root.tar.gz |grep zoneinfo lrwxrwxrwx root/root 0 2018-05-24 13:44 etc/localtime -> /usr/share/zoneinfo/UTC $ This is despite the fact that the tzdata package itself is not installed. In bionic, this symlink is not present: $ tar tvf ubuntu-bionic-core-cloudimg-amd64-root.tar.gz |grep zoneinfo $ This is in fact a deliberate change in bionic as part of the minimal image work; in livecd-rootfs live-build/auto/build: if [ "${SUBPROJECT:-}" = minimized ] \ && ! Chroot chroot dpkg -l tzdata 2>&1 |grep -q ^ii; then # workaround for tzdata purge not removing these files rm -f chroot/etc/localtime chroot/etc/timezone fi The behavior you're seeing in bionic is the *expected* behavior on a completely fresh install of the tzdata package. The reason you don't see this behavior in prior releases is that it's not truly a fresh install, and there is cruft left on the filesystem in the form of /etc/localtime. If /etc/localtime already exists, tzdata has no need to prompt instead of using the existing configuration on the system. If it doesn't exist, tzdata will ask debconf, which means a prompt by default. So your setting DEBIAN_FRONTEND=noninteractive, if you don't care about /etc/localtime and just tzdata to use the default, is the correct fix here. ** Changed in: tzdata (Ubuntu) Status: New => Invalid -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1773687 Title: [bionic] no unattended installation To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/tzdata/+bug/1773687/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs