-- Install package without confirm and keep old config file:
apt-get install -o Dpkg::Options::="--force-confold" --force-yes -y ntp
-- Remove hold package:
- List hold packge:
dpkg --get-selections | grep hold - Remove hold
echo "package_name install" | dpkg --set-selections
More information: https://raphaelhertzog.com/2010/09/21/debian-conffile-configuration-file-managed-by-dpkg/