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A metapackage, as used by CDDs, is a Debian package that contains:
Dependencies on other Debian packages (essential)
Use "Depends" for packages that are definitely needed for all basic stuff of the CDD in question.
The packages that are listed as "Recommends" in the tasks file should be installed on the machine where the metapackage is installed and which are needed to work on a specific task.
Use "Suggests" for others of lesser importance that might be possibly useful, or non-free packages. When a package is not available for the target distribution at metapackage build time the "Recommends" is turned into a "Suggests" to enable a flawless installation of the metapackage.
Menu entries (recommended)
Place these in
/etc/cdd/<cdd>/menu/<pkg-name>
Maintain these via role based tools
Configuration stuff (optional)
debconf
questions or pre-seeding
cfengine
scripts (or similar see Enhancing basic technologies
regarding Custom Debian Distributions, Section 9.4)
Special metapackages:
<cdd>-tasks
: Contains information for
tasksel
<cdd>-config
: Special configurations, basic stuff
for user menus
Metapackages are small packages with nearly no contents. The main feature of
this type of package is its dependencies on other packages. The naming of
metapackages follows the pattern <cdd>-<task>
where <cdd> stands for the short name of a Custom Debian
Distribution, e.g. junior
for Debian Jr. or med
for
Debian-Med, and <task> means the certain task inside the
Custom Debian Distribution, e.g. puzzle or bio.
Examples:
junior-puzzle
Debian Jr. Puzzles
education-tasks
Tasksel files for SkoleLinux systems
med-bio
Debian-Med micro-biology packages
When using metapackages, no research for available software inside Debian is necessary. It would not be acceptable for normal users to have to browse the descriptions of the whole list of the 10000 packages in Debian to find everything they need. So, metapackages are an easy method to help users to find the packages that are interesting for their work quickly.
If the author of a metapackage includes several packages with similar functionality, an easy comparison between software covering the same task is possible.
Moreover, the installation of a metapackage ensures that no package that is necessary for the intended task can be removed without explicit notice that also the metapackage has to be removed. This helps non specialist administrators to keep the installation fit for the specialized users.
By defining conflicts with some other packages inside the metapackage, it is possible to ensure that a package that might conflict for some reasons for the intended task can not be installed at the same time as the metapackage is installed.
All in all, metapackages enable an easy installation from scratch, and keep the effort required for administration low.
Besides the simplification of installing relevant packages by dependencies
inside metapackages, these packages might contain special configuration for the
intended task. This might either be accomplished by pre-seeding
debconf
questions, or by modifying configuration files in a
postinst
script. It has to be ensured that no changes that have
been done manually by the administrator will be changed by this procedure. So
to speak, the postinst
script takes over the role of a local
administrator.
A "traditional" weakness of Free Software projects is missing
documentation. To fix this, Custom Debian Distributions try to provide
relevant documentation to help users to solve their problems. This can be done
by building *-doc
packages of existing documentation, and by
writing extra documentation, like manpages, etc. By supplying documentation,
Custom Debian Distributions fulfil their role in addressing the needs of
specialised users, who have a great need for good documentation in their native
language.
Thus, translation is a very important thing to make programs more useful for
the target user group. Debian has established a Debian Description Translation
Project
, which has the goal to translate package descriptions.
There is a good chance this system could also be used for other types of
documentation, which might be a great help for Custom Debian Distributions.
In short, there are no special tools available to handle metapackages nicely. But there are some tricks that might help, for the moment.
apt-cache
The program apt-cache
is useful to search for relevant keywords in
package descriptions. With it, you could search for a certain keyword
connected to your topic (for instance "med") and combine
it reasonably with grep
:
~> apt-cache search med | grep '^med-' med-bio - Debian-Med micro-biology packages med-common-dev - Debian-Med Project common files for developing... med-dent - Debian-Med package for dental practice client med-doc - Debian-Med documentation packages med-imaging - Debian-Med imaging packages med-imaging-dev - Debian-Med packages for medical image develop... med-tools - Debian-Med several tools med-bio-contrib - Debian-Med micro-biology packages (contrib an... med-common - Debian-Med Project common package med-cms - Debian-Med content management systems
This is not really straightforward, and absolutely unacceptable for end users.
grep-dctrl
The program grep-dctrl
is a grep for Debian package information,
which is helpful for extracting specific package details matching certain
patterns:
~> grep-dctrl ': med-' /var/lib/dpkg/available | \ grep -v '^[SIMAVF]' | \ grep -v '^Pri' Package: med-imaging Depends: paul, ctsim, ctn, minc-tools, medcon, xmedcon, med-common Description: Debian-Med imaging packages Package: med-dent Depends: debianutils (>= 2.6.2), mozilla-browser | www-browser, ... Description: Debian-Med package for dental practice client Package: med-bio Depends: bioperl, blast2, bugsx, fastdnaml, fastlink, garlic... Description: Debian-Med micro-biology packages Package: med-common Depends: adduser, debconf (>= 0.5), menu Description: Debian-Med Project common package Package: med-common-dev Depends: debconf (>= 0.5) Description: Debian-Med Project common files for developing ... Package: med-tools Depends: mencal, med-common Description: Debian-Med several tools Package: med-doc Depends: doc-linux-html | doc-linux-text, resmed-doc, med-co... Description: Debian-Med documentation packages Package: med-cms Depends: zope-zms Description: Debian-Med content management systems Package: med-imaging-dev Depends: libgtkimreg-dev, ctn-dev, libminc0-dev, libmdc2-dev... Description: Debian-Med packages for medical image development Package: med-bio-contrib Depends: clustalw | clustalw-mpi, clustalx, molphy, phylip, ... Description: Debian-Med micro-biology packages (contrib and ...
This is, like the apt-cache
example, also a bit
cryptic, and again is not acceptable for end users.
auto-apt
The program auto-apt
is really cool if you are running a computer
that was installed from scratch in a hurry, and are sitting at a tradeshow
booth preparing to do a demo. If you had no time to figure out which packages
you needed for the demo were missing so you could install all of them in
advance, you could use auto-apt
in the following manner to
guarantee that you have all of the files or programs you need:
~> sudo auto-apt update put: 880730 files, 1074158 entries put: 903018 files, 1101981 entries ~> auto-apt -x -y run Entering auto-apt mode: /bin/bash Exit the command to leave auto-apt mode. bash-2.05b$ less /usr/share/doc/med-bio/copyright Reading Package Lists... Done Building Dependency Tree... Done The following extra packages will be installed: bugsx fastlink readseq The following NEW packages will be installed: bugsx fastlink med-bio readseq 0 packages upgraded, 4 newly installed, 0 to remove and 183 ... Need to get 0B/1263kB of archives. After unpacking 2008kB wi... Reading changelogs... Done Selecting previously deselected package bugsx. (Reading database ... 133094 files and directories currently... Unpacking bugsx (from .../b/bugsx/bugsx_1.08-6_i386.deb) ... Selecting previously deselected package fastlink. Unpacking fastlink (from .../fastlink_4.1P-fix81-2_i386.deb) ... Selecting previously deselected package med-bio. Unpacking med-bio (from .../med-bio_0.4-1_all.deb) ... Setting up bugsx (1.08-6) ... Setting up fastlink (4.1P-fix81-2) ... Setting up med-bio (0.4-1) ... localepurge: checking for new locale files ... localepurge: processing locale files ... localepurge: processing man pages ... This package is Copyright 2002 by Andreas Tille <tille@debian.org> This software is licensed under the GPL. On Debian systems, the GPL can be found at /usr/share/common-... /usr/share/doc/med-bio/copyright
Just do your normal business - in the above example, less
/usr/share/doc/med-bio/copyright - and if the necessary package is not
yet installed, auto-apt
will care for the installation and proceed
with your command. While this is really cool, this is not really
intended for a production machine.
The short conclusion here is: There are no sophisticated tools that might be helpful to handle metapackages as they are used in Custom Debian Distributions - just some hacks using the powerful tools inside Debian.
dselect
This good old package handling tool provides no special help to handle metapackages in an elegant manner.
tasksel
The Debian task installer Tasksel
is the first interface for
package selection that is presented to the user when installing a new computer.
The End-user section should contain an entry for each Custom
Debian Distribution. This is currently the case for Debian-Jr.
Debian Task Installer v1.43 - (c) 1999-2003 SPI and others ————— Select tasks to install ————— –– End-user –––– [X] Debian Jr. [ ] Desktop environment [ ] Games [ ] Linux Standard Base [ ] X window system [ ] Office environment –– Hardware Support –––– [ ] Dialup internet [ ] Laptop [ ] Broadband internet connection –– Servers –––– [ ] DNS server [ ] File server [ ] Mail server [ ] Usenet news server [ ] SQL database [ ] Print server [ ] Conventional Unix server <Finish> <Task Info> <Help>
Unfortunately, there are some issues that prevent further Custom Debian
Distributions from being included in the tasksel
list, because the
dependencies of this task can affect what appears on the first installation CD.
This problem would be even greater if all Custom Debian Distributions were
added, and so a different solution has to be found here. (See #186085
.) In principle,
tasksel
is a good tool for easy installation of Custom Debian
Distributions.
aptitude
This is a better replacement for dselect
, and has some useful
support for searching for and grouping of packages. While this is not bad, it
was not intended for the purpose of handling Custom Debian Distributions, and
thus there could be some better support to handle metapackages more cleverly.
Short conclusion: There is a good chance metapackages could be handled nicely by the text based Debian package administration tools, but this is not yet implemented.
Debian Woody does not contain a really nice graphical user interface for the Debian package management system. But the efforts to support users with an easy to use tool have increased, and so there there will be some usable options in Sarge.
gnome-apt
This is the native GNOME flavour of graphical user interfaces to apt. It has a nice Search feature that can be found in the Package menu section. If for instance the packages of the Debian Jr. project come into the focus of interest a search for "junior-*" will show up all related packages including their descriptions. This will give a reasonable overview about metapackages of the project.
synaptic
Even more sophisticated and perhaps the best choice for users of Custom Debian
Distributions. Synaptic
has a nice filter feature, which makes it
a great tool here. Moreover synaptic
is currently the only user
interface that supports Debian Package Tags (see Debian Package Tags, Section 9.3).
kpackage
This is the user interface of choice for KDE lovers. Regarding its features (with exception of Debian Package Tags) it is similar to both above.
Short conclusion: As well as the text based user interfaces these tools are quite usable but need enhancements to be regarded as powerful tools for Custom Debian Distributions.
Web search
Debian has a web interface that can be used to search for certain substrings in package names. For instance if you are searching the meta packages of Debian-Med you could point your favourite Browser to
http://packages.debian.org/cgi-bin/search_packages.pl?keywords=med-\|[amp
]\|subword=1
As a result you will get a list of all Debian-Med packages.
Package Tracking System
The Package Tracking System is a really great tool that provides essential information about packages. Regarding Custom Debian Distributions it can help if you know the Debian user name of the developer who is responsible for the metapackages:
The other way to use the Package Tracking System is to search for packages starting with a certain letter:
But the list that is obtained by this method is much larger than it would be useful for a good overview.
So the conclusion is - we just need better support here for Custom Debian Distributions.
list-junior.sh
The package junior-doc
contains a script
/usr/share/doc/junior-doc/examples/scripts/list-junior.sh
that
checks for the installed packages of a Custom Debian Distribution and builds a
simple web page describing these packages. (The BTS contains a patch to let
this script work also for other Custom Debian Distributions.)
Short conclusion: Some very basic things can be done with the web interfaces described above but techniques have to be developed to provide useful information about each Custom Debian Distribution.
Obviously there are no nifty tools as you might know them from Debian available
yet. The user interfaces for apt-get
have to be enhanced
drastically to make them easy enough to make them useful in the hands of an end
user. This might implicitly mean that we need some additional control fields
in dpkg
to implement reasonable functionality. The following
items are target of future development:
Searching for existing metapackages
Overview about dependencies of these metapackages
Enhancing tools like aptitude
, synaptic
, etc.
Special tasksel
section
Web tools that keep metapackage information up to date
Furthermore it is necessary to find a set of keywords for each Custom Debian Distribution and write a tool to search these keywords comfortable. The best way to accomplish this might be to make use of Debian Package Tags, which is a quite promising technique.
Tools that grep the apt cache directly for metapackages have to be written or rather the available tools for this should be patched for this actual functionality.
As stated above specialists have only interest in a subset of the available software on the system they are using. In an ideal world, this would be the only software that is presented in the menu. This would allow the user to concentrate on his real world tasks instead of browsing large menu trees with entries he does not understand.
To accomplish this, a technique has to be implemented that allows to define a
set of users who get a task-specific menu while getting rid of the part of
software they are not interested in. Moreover this has to be implemented for
certain groups of users of one Custom Debian Distribution, which are called
"roles". There are several techniques available to manage user
roles. Currently in the field of Custom Debian Distributions a UNIX group
based role system is implemented. This means, that a user who belongs to a
certain group of a Custom Debian Distribution is mentioned in the
/etc/group
file in the appropriate group and gets a special user
menu that is provided for exactly this group.
Strictly speaking it is not the best solution to conflate a configuration mechanism, which users see with menus, with access control, i.e. unix groups. It might be confusing, and wastes the limited number of groups to which a user can belong. On the other hand this is a solution that works for the moment, and has no real negative impact on the general use of the system. The benefit of using unix groups is that there is a defined set of tools provided to handle user groups. This makes life much easier; there is no practical limit to the number of groups to which a user may belong for the existing Custom Debian Distributions at this time.
In the long run, this role system might even be enhanced to certain "levels" a user can have and here the UNIX groups approach will definitely fail and has to be replaced by other mechanisms. This will include the possibility to enable the user adjust his own level ("novice", "intermediate", "expert") while only the administrator is able to access the UNIX groups. On the other hand such kind of user level maintenance is not only a topic for Custom Debian Distributions but might be interesting for Debian in general.
Another point that speaks against using UNIX groups for role administration is the fact that local administrators are not in all cases competent enough to understand the UNIX role concept as a security feature and thus a real role concept including tools to maintain roles are needed in the future.
The handling of the user menus according to the groups is implemented in a flexible plugin system and other ways of handling groups (i.e. LDAP) should be easy to implement.
The Debian menu system cares for menu updates after each package installation.
To enable compliance with the role based menu approach it is necessary
to rebuild the user menu after each package installation or after adding new
users to the intended role. This can be done by using the
cdd-update-menus(8)
(see cdd-update-menus(8),
Section A.2.2) script from cdd-common
. It has to be said that
using cdd-update-menus
is not enough to change the menu of a user.
To accomplish this a call of the general update-menu
script for
every single user of a Custom Debian Distribution is necessary if this is not
done by the postinst
script of a metapackage. This can easily
been done if the configuration file of a Custom Debian Distribution
/etc/cdd/<cdd>/<cdd>.conf
contains the line
UPDATEUSERMENU=yes
It is strongly suggested to use the package cdd-dev
to build
metapackages of a Custom Debian Distribution that will move all necessary files
right into place if there exists a menu
directory with the menu
entries. Note, that the users ${HOME}/.menu
directory remains
untouched.
debconf
Using cdd-dev
it is very easy to build a
cdd-config
package that contains debconf
scripts to configure system users who should belong to the group of users of
the Custom Debian Distribution cdd. For example see the
med-common
package.
~> dpkg-reconfigure med-common Configuring med-common ---------------------- Here is a list of all normal users of the system. Now you can select those users who should get a Debian-Med user menu. 1. auser (normal user A) 6. fmeduser (med user F) 2. bmeduser (med user B) 7. glexuser (lex user G) 3. cjruser (jr user C) 8. hmeduser (med user H) 4. djruser (jr user D) 9. iadmin (administrator I) 5. eadmin (administrator E) 10. juser (normal user J) (Enter the items you want to select, separated by spaces.) :-! Please specify the Debian-Med users! 2 8
This example shows the situation when you dpkg-reconfigure
med-common
if med user B and med user H were
defined as users of Debian-Med previously and med user F should be
added to the group of medical staff. (For sure it is more convenient to use
the more comfortable interfaces to debconf
but the used SGML DTD
does not yet support screen
shots
.)
Building a metapackage is more or less equal for each meta package. This was
the reason to build a common source package cdd
that builds into
two binary packages
cdd-dev
Helpful tools to build metapackages from a set of template files. These tools are interesting for people who want to build metapackages in the style Debian-Edu and Debian-Med are currently doing this. The purpose of this package is to make maintenance of metapackages as easy as possible.
This package is described in detail in appendix Package cdd-dev
,
Section A.1.
cdd-common
This package provides some files that are common to meta packages of Common
Debian Distributions especially those that were built using the tools of the
package cdd-dev
. It introduces a method to handle system users in
a group named according to the name of the Custom Debian Distribution. The
user menu approach is explained in detail in User roles,
Section 6.3.
This package is described in detail in appendix Package
cdd-common
, Section A.2.
The usage of the tools that are contained in these packages are described now in detail.
The tool simple-cdd
is a limited though relatively easy tool to
create a customized debian-installer CD.
It includes simple mechanisms to create "profiles" that define common
system configurations, which can be selected during system installation.
Simple-cdd
also makes it easy to build CDs with language and
country settings pre-configured, or to use a 2.6 kernel by default.
This can be used to create a crude "Custom Debian Distribution" using
packages from debian, with pre-configuration of packages that use
debconf
. Custom configuration scripts can be specified to handle
packages that don't support debconf
pre-configuration.
Testing CD images with qemu
is also made simple with a provided
script.
It has only been tested with debian-cd
from sarge (other than
debpartial-mirror
), so if using a new debian-cd
or
debian-installer
, it may require some tweaks.
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Custom Debian Distributions
5 November 2008tille@debian.org