< Previous | Contents | Next >
Preseeding makes use of the debconf framework. This framework is the preferred mechanism used in Ubuntu to interact with the user when configuring packages and also forms the heart of debian-installer. In the debconf framework questions or dialogs are based on templates. There are different types of templates for different types of questions. The actual questions are “generated” from templates at runtime; multiple questions can use the same template.
The following types of templates are relevant for preseeding.
• string: allows the user to type any value
• password: similar to string but the value typed is not displayed
• boolean: for yes/no or true/false type of questions
• select: allows the user to select one option from a list
• multiselect: allows the user to select zero, one or more options from a list
• note: used to display a message
In debian-installer templates are stored in a readable file
/var/cache/debconf/templates.dat. This file contains all fixed text and all translations. It can also contain a default value for the template. The fixed text can include variables that will be replaced at runtime.
Another readable file /var/cache/debconf/questions.dat is used to store the values for vari- ables and the answers given to questions. A question always refers to the template used to ask it. For obvious security reasons the values for questions of type “password” are stored in a separate, non-readable file in the same directory.