~ubuntu-branches/ubuntu/maverick/tasksel/maverick

The interface uses debconf for consistency with the rest of the Debian

installer.

On startup, the tasksel program will read all *.desc files in

/usr/share/tasksel/ for information about what tasks are available. The

tasks will be presented in a simple list selection screen with their short

descriptions.

On exit, tasksel executes the appropriate command to install the selected

packages. If the -t option is given, then tasksel prints out the command

line to use to stdout instead. All other messages are printed to stderr.

To get a new task added to Debian, please file a bug report on tasksel.

Debian derived distributions can add a new .desc file to

/usr/share/tasksel/ to add additional tasks, or modify/divert

debian-tasks.desc to remove tasks.

The file format is a rfc-822 style stanza, with fields named Task, Section,

Description (which should include an extended description), Key, Packages, 

Enhances, Test- and Relevance fields. Here is an example:

Task: graphical-games

Section: user

Relevance: 10

Description: Graphical games

 This task provides a variety of graphical games. Old-school unix games are

 not included.

Key:

 x-window-system-core

Packages: list

 quake

 myst

 monkey-island

The Key field lists packages that are essential to the task. If those

packages are not available, then the task will not be available either. It

need not list all the packages in the task, if some only serve to make it

better when they are available.

The Packages field tells how to get a complete list of packages that are in

the task. In the example above, it uses the "list" method, which is defined

in /usr/lib/tasksel/packages/list. This simple method just lets you list

the packages you want to include in the task in the following lines.

All Key packages will be also be selected for installation when a task is

installed.

In Debian, we mostly use the "task-fields" method, which is built into

tasksel, and looks for Task fields in the control data of available

packages, that list the name of the task. Another available method is

"standard", which just installs all standard priority packages, and another

is "manual", which, as a special case, runs aptitude interactively to

select what to install.

It's also possible to define other methods, by adding programs to

/usr/lib/tasksel/packages/. Then list the name of the program as the first

word of the task field, and it will be run and passed the name of the task as

its first parameter and any further lines of the task field as its other

parameters, and should output a list of packages in that task. The "list"

method described above is a simple example of such a program.

There is support for automatically installing tasks based on test programs.

If a task has a Test-* field, then a program in /usr/lib/tasksel/tests/

will be run. For example Test-lang fields cause /usr/lib/tasksel/tests/lang

to be run. The test is passed first the name of the task, and then the

contents of the field as parameters. The exit code of the test controls

what to do with the task:

0 - do not display, but do install task

1 - do not display task 

2 - display task, marked for installation

3 - display task, not marked for installation

One use of these tests is in automatically selecting a language task

appropriate for the user's locale, and hiding the rest. The lang test

handles this by comparing the value of the Test-lang field of a task with

the locale setting. Tests could also be used for things like automatically

installing hardware support tasks on systems with the right hardware.

There is support for tasks that enhance other tasks. If a task has a

Enhances field, then it should only be installed if all the tasks

listed as in that field are installed. For example, a french-desktop task

enchances a system that has both the french and desktop tasks, and will be

automatically installed on such a system but not others. Such tasks are

hidden from the menu.

If two tasks both enhance the same task (ie, gnome-desktop and kde-desktop

enhancing desktop), but only one should be selected, this can be

accomplished by adding Test-* fields.

If a task is important enough that it should go near the top of its

section, give it a relevance of 9 or 10. If a task is not likely to be

used, give it a relevance of 1. Default is 5.

tasksel also supports preinst, postinst, prerm, and postrm scripts for

tasks. These are run before a task is installed, and after it is removed as

with the dpkg scripts. These scripts sould be installed in

/usr/lib/tasksel/info/, for example, /usr/lib/tasksel/info/desktop.preinst.

Currently they are passed no parameters, but this might change later. These

scripts should take care not to output anything to stdout. You are not

encouraged to use these scripts to install any packages, as in some

situations apt can hang prompting for a CD switch if run from one of these

scripts.