Debconf: a configuration system for Debian packages

for unattended installations

Ansible module: http://docs.ansible.com/ansible/debconf_module.html

debconf-show

query the debconf database

$ debconf-show postfix
* postfix/main_mailer_type: 'Internet Site'
  postfix/chattr: false
* postfix/mailname: your.hostname.com
...

debconf-get-selections

output contents of debconf database

$ debconf-get-selections | grep postfix
postfix postfix/mailname    string  your.hostname.com
postfix postfix/main_mailer_type    string  'Internet Site'
...

debconf-set-selections

insert new values into the debconf database

$ echo "postfix postfix/mailname string your.hostname.com" | debconf-set-selections
$ echo "postfix postfix/main_mailer_type string 'Internet Site'" | debconf-set-selections
$ apt-get -y install postfix

single line noninteractive

$ DEBIAN_FRONTEND=noninteractive apt-get install postfix

dpkg-reconfigure

reconfigure an already installed package

$ dpkg-reconfigure debconf