How do I ask apt-get to skip any interactive post-install configuration steps?
You can do a couple of things for avoiding this. Setting the DEBIAN_FRONTEND variable to noninteractive and using -y flag. For example:
export DEBIAN_FRONTEND=noninteractive
apt-get -yq install [packagename]
If you need to install it via sudo, use:
sudo DEBIAN_FRONTEND=noninteractive apt-get -yq install [packagename]