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Metapackages</a></span></dt><dd><dl><dt><span class="sect2"><a href="ch06.html#defmetapackages">6.1.1. Metapackage definition</a></span></dt><dt><span class="sect2"><a href="ch06.html#collection">6.1.2. Collection of specific software</a></span></dt><dt><span class="sect2"><a href="ch06.html#categorisation">6.1.3. Packages showing up in more than one metapackage</a></span></dt><dt><span class="sect2"><a href="ch06.html#configuration">6.1.4. Adapted configuration inside metapackages</a></span></dt><dt><span class="sect2"><a href="ch06.html#documentation">6.1.5. Documentation packages</a></span></dt></dl></dd><dt><span class="sect1"><a href="ch06.html#mp_handling">6.2. Handling of metapackages</a></span></dt><dd><dl><dt><span class="sect2"><a href="ch06.html#cmdline">6.2.1. Command line tools</a></span></dt><dt><span class="sect2"><a href="ch06.html#text_ui">6.2.2. Text user interfaces</a></span></dt><dt><span class="sect2"><a href="ch06.html#gui">6.2.3. Graphical user interfaces</a></span></dt><dt><span class="sect2"><a href="ch06.html#web_if">6.2.4. Web interfaces</a></span></dt><dt><span class="sect2"><a href="ch06.html#future_handling">6.2.5. Future handling of metapackages</a></span></dt></dl></dd><dt><span class="sect1"><a href="ch06.html#userroles">6.3. User roles</a></span></dt><dd><dl><dt><span class="sect2"><a href="ch06.html#menu_tools">6.3.1. User menu tools</a></span></dt></dl></dd><dt><span class="sect1"><a href="ch06.html#devtools">6.4. Development tools</a></span></dt><dt><span class="sect1"><a href="ch06.html#namespace">6.5. Dealing with name space pollution</a></span></dt></dl></div><div class="sect1"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="metapackages"></a>6.1. Metapackages</h2></div></div></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a name="defmetapackages"></a>6.1.1. Metapackage definition</h3></div></div></div><p>
A metapackage, as used by Blends, is a Debian package that contains:
</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>Dependencies on other Debian packages (essential)</p><div class="variablelist"><dl class="variablelist"><dt><span class="term">Depends</span></dt><dd><p>Use "Depends" for packages that are definitely needed
for all basic stuff of the Blend in question.</p></dd><dt><span class="term">Recommends</span></dt><dd><p>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.</p></dd><dt><span class="term">Suggests</span></dt><dd><p>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.</p></dd></dl></div></li><li class="listitem"><p>Menu entries (recommended)</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: circle; "><li class="listitem"><p>Place these in <code class="filename">/etc/blends/</code><code class="varname"><blend></code>
<code class="varname">/menu/</code><code class="varname"><pkg-name></code>
</p></li><li class="listitem"><p>Maintain these via role based tools</p></li></ul></div></li><li class="listitem"><p>Configuration stuff (optional)</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: circle; "><li class="listitem"><p><span class="orgname">debconf</span> questions or pre-seeding</p></li><li class="listitem"><p><span class="orgname">cfengine</span> scripts (or similar see <a class="xref" href="ch09.html#EnhancingTechnology" title="9.4. Enhancing basic technologies regarding Debian Pure Blends">Section 9.4, “Enhancing basic technologies regarding Debian Pure Blends”</a>)</p></li></ul></div></li><li class="listitem"><p>Special metapackages:</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: circle; "><li class="listitem"><p><code class="varname"><blend></code>-<span class="package">tasks</span>:
Contains information for <span class="orgname">tasksel</span></p></li><li class="listitem"><p><code class="varname"><blend></code>-<span class="package">config</span>:
Special configurations, basic stuff for user menus</p></li></ul></div></li></ul></div><p>
</p><p>
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
<code class="varname"><blend></code>-<code class="varname"><task></code>
where <code class="varname"><blend></code> stands for the short name of a Debian
Pure Blend, e.g. <span class="package">junior</span> for Debian
Jr. or <span class="package">med</span> for Debian Med,
and <code class="varname"><task></code> means the certain task inside the Blend,
e.g. puzzle or bio.
</p><p>
Examples:
</p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><span class="package">junior-puzzle</span></span></dt><dd><p>Debian Jr. Puzzles</p></dd><dt><span class="term"><span class="package">education-tasks</span></span></dt><dd><p>Tasksel files for SkoleLinux systems</p></dd><dt><span class="term"><span class="package">med-bio</span></span></dt><dd><p>Debian Med micro-biology packages</p></dd></dl></div><p>
</p></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a name="collection"></a>6.1.2. Collection of specific software</h3></div></div></div><p>
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 20000 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.
</p><p>
If the author of a metapackage includes several packages with similar
functionality, an easy comparison between software covering the same task is
possible.
</p><p>
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.
</p><p>
All in all, metapackages enable an easy installation from scratch, and
keep the effort required for administration low.
</p></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a name="categorisation"></a>6.1.3. Packages showing up in more than one metapackage</h3></div></div></div><p>
This seems to be an FAQ: If a package <span class="package">A</span> is in the list of
dependencies of metapackage <span class="package">m</span> is it allowed or reasonable to
add it to the list of dependencies of metapackage <span class="package">n</span>?
</p><p>
The answer is: Why not?
</p><p>
The "overlap" is no problem because we do not want to build
an exclusive categorisation which might be hard to understand for our
users. Metapackages are like "normal" packages: Nobody
would assume that because package <span class="package">x</span> depends from package
<span class="package">libc</span> no other package is allowed to add <span class="package">libc</span> to its
depends. So why not adding a dependency to more than one metapackage if
it is just useful for a certain task?
</p><p>
The important thing is to support our users. A specific user wants to
solve a certain task (and thus installs a certain metapackage). The
question whether some Dependencies are also mentioned in a different
metapackage is completely useless for this task. So in fact we do
<span class="emphasis"><em>not</em></span> build a categorisation tree but build pools of useful
software for certain tasks which can definitely have overlaps.
</p><p>
To give a certain example which was asked by a member of Debian
Multimedia team: A user who is seeking for his optimal sound player is
not served best if we "hide" an application from his view by
including it into sound recorders exclusively. While chances might be
good that a sound recorder is not as lightweight as a pure player the
user will find out this quickly if he is looking for only a
lightweight player - but perhaps he becomes happy later about the
"added value" of his favourite player if it also is able to record
sound.
</p></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a name="configuration"></a>6.1.4. Adapted configuration inside metapackages</h3></div></div></div><p>
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 <span class="orgname">debconf</span> questions, or by
modifying configuration files in a <span class="package">postinst</span> 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
<span class="package">postinst</span> script takes over the role of a local
administrator.
</p></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a name="documentation"></a>6.1.5. Documentation packages</h3></div></div></div><p>
A "traditional" weakness of Free Software projects is missing
documentation. To fix this, Debian Pure Blends try to provide
relevant documentation to help users to solve their problems. This
can be done by building <span class="package">*-doc</span> packages of existing
documentation, and by writing extra documentation, like manpages, etc.
By supplying documentation, Debian Pure Blends fulfil their role in
addressing the needs of specialised users, who have a great need for
good documentation in their native language.
</p><p>
Thus, translation is a very important thing to make programs more
useful for the target user group. Debian has established
a <a class="ulink" href="http://ddtp.debian.net/" target="_top">Debian Description
Translation Project</a>, 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
Debian Pure Blends.
</p></div></div><div class="sect1"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="mp_handling"></a>6.2. Handling of metapackages</h2></div></div></div><p>
In short, there are no special tools available to handle metapackages
nicely. But there are some tricks that might help, for the moment.
</p><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a name="cmdline"></a>6.2.1. Command line tools</h3></div></div></div><p>
</p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><span class="orgname">apt-cache</span></span></dt><dd><p>
The program <span class="orgname">apt-cache</span> 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
"<span class="package">med</span>") and combine it reasonably with <span class="package">grep</span>:</p><div class="informalexample"><pre class="programlisting">
~> apt-cache search med | grep '^med-'
med-bio - Debian Med micro-biology packages
med-bio-dev - Debian Med micro-biology development packages
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-common - Debian Med Project common package
med-cms - Debian Med content management systems
</pre></div><p>
This is <span class="emphasis"><em>not really straightforward</em></span>, and
absolutely unacceptable for end users.
</p></dd><dt><span class="term"><span class="package">grep-dctrl</span></span></dt><dd><p>
The program <span class="package">grep-dctrl</span> is a grep for Debian package
information, which is helpful for extracting specific package details
matching certain patterns:</p><div class="informalexample"><pre class="programlisting">
~> 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-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-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 ...
</pre></div><p>
This is, like the <span class="package">apt-cache</span> example, <span class="emphasis"><em>also
a bit cryptic</em></span>, and again is not acceptable for end users.
</p></dd><dt><span class="term"><span class="package">auto-apt</span></span></dt><dd><p>
The program <span class="package">auto-apt</span> 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
<span class="package">auto-apt</span> in the following manner to guarantee that you
have all of the files or programs you need:</p><div class="informalexample"><pre class="programlisting">
~> 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
</pre></div><p>
Just do your normal business - in the above example, <code class="filename">less
/usr/share/doc/med-bio/copyright</code> - and if the necessary
package is not yet installed, <span class="package">auto-apt</span> will care for
the installation and proceed with your command. While this is
really cool, this is <span class="emphasis"><em>not really intended for a production
machine</em></span>.
</p></dd></dl></div><p>
The short conclusion here is: <span class="emphasis"><em>There are no sophisticated tools
that might be helpful to handle metapackages as they are used in
Debian Pure Blends - just some hacks using the powerful tools inside
Debian.</em></span>
</p></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a name="text_ui"></a>6.2.2. Text user interfaces</h3></div></div></div><p>
</p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><span class="orgname">tasksel</span></span></dt><dd><p>
The Debian task installer <span class="package">Tasksel</span> is the first
interface for package selection that is presented to the user when
installing a new computer. The <span class="package">End-user</span> section should
contain an entry for each Debian Pure Blend.
Unfortunately, there are some issues that prevent Blends
from being included in the <span class="package">tasksel</span> list,
because the dependencies of this task can affect what appears on
the first installation CD. This problem would be even greater if
all Blends were added, and so a different solution has
to be found here. (See <a class="ulink" href="http://bugs.debian.org/186085" target="_top">#186085</a>.)
In principle, <span class="package">tasksel</span> is a good
tool for easy installation of Blends.
</p><p>
As a workaround for this problem the <span class="package">blends-dev</span>
framework creates a package <span class="package">BLEND-tasks</span> which contains
a <span class="package">tasksel</span> control file. If you install this package
all tasks of the Blend will be added to the default list of tasks
inside <span class="package">tasksel</span>. So a solution for Blend specific
installation media might be to just remove the default tasksel
list and provide the Blends own tasks exclusively.
</p></dd><dt><span class="term"><span class="package">aptitude</span></span></dt><dd><p>
This is a better replacement for <span class="package">dselect</span>, 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 Debian Pure Blends, and thus there could be some better
support to handle metapackages more cleverly.</p></dd></dl></div><p>
Short conclusion: <span class="emphasis"><em>There is a good chance metapackages could be
handled nicely by the text based Debian package administration tools,
but this is not yet implemented.</em></span>
</p></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a name="gui"></a>6.2.3. Graphical user interfaces</h3></div></div></div><p>
Debian <span class="emphasis"><em>Woody</em></span> 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.
</p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><span class="package">gnome-apt</span></span></dt><dd><p>This is the native GNOME flavour of graphical user interfaces
to apt. It has a nice <span class="package">Search</span> feature that can be
found in the <span class="package">Package</span> menu section. If for instance
the packages of the Debian Jr. project come into the focus of
interest a search for "<span class="package">junior-*</span>" will show
up all related packages including their descriptions. This
will give a reasonable overview about metapackages of the
project.</p></dd><dt><span class="term"><span class="package">synaptic</span></span></dt><dd><p>Even more sophisticated and perhaps the best choice for users
of Debian Pure Blends. <span class="package">Synaptic</span> has a nice
filter feature, which makes it a great tool here.
Moreover <span class="package">synaptic</span> is currently the only user
interface that supports Debian Package Tags
(see <a class="xref" href="ch09.html#debtags" title="9.3. Debian Package Tags">Section 9.3, “Debian Package Tags”</a> ).</p></dd><dt><span class="term"><span class="package">kpackage</span></span></dt><dd><p>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.</p></dd></dl></div><p>
Short conclusion: <span class="emphasis"><em>As well as the text based user interfaces
these tools are quite usable but need enhancements to be regarded as
powerful tools for Debian Pure Blends.</em></span>
</p></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a name="web_if"></a>6.2.4. Web interfaces</h3></div></div></div><p>
</p><div class="variablelist"><dl class="variablelist"><dt><span class="term">Tasks pages</span></dt><dd><p>The tasks pages probably provide the best overview about
the actual work which is done in a Debian Pure Blend. These
pages are automatically generated by reading the tasks files
(see <a class="xref" href="apa.html#debian_control" title="A.1.2. debian/control">Section A.1.2, “<code class="filename">debian/control</code>”</a> ) and verifying the existence
of the packages that are mentioned as dependencies. On the
resulting web page the packages are listed with some meta
information and the description of the package. As user
oriented pages they are translated into more than 10
languages while translated means, the navigation text of the
page generating code is using <span class="package">gettext</span> which
enables translation (the work is not yet completely done for
all languages) but even more importantly the descriptions of
the packages are translated as well by using the information
from
<a class="ulink" href="http://ddtp.debian.net/" target="_top">Debian Description Translation Project</a>.
</p><p>These tasks pages are available via
</p><div class="informalexample"><pre class="programlisting">
http://blends.debian.org/BLEND/tasks
</pre></div><p>
where <span class="package">BLEND</span> has to be replaced by the name of the
Blend. Currently these pages are available for the Blends:
</p><div class="informalexample"><pre class="programlisting">
accessibility, edu, gis, junior, lex, med, science, debichem
</pre></div><p>
In short: If you want to know more about a specific Blend
go to its task page and have a look what is listed there.
</p></dd><dt><span class="term">Bugs pages</span></dt><dd><p>The more developer oriented bugs pages try to match the
scope of the tasks pages mentioned above but there is no
description of the packages given but rather the bugs that
are reported in the Debian Bug Tracking System (BTS) are
listed there. This is a quite valuable source of information
if somebody is interested in increasing the quality of a
Blend: Fixing bugs is always welcome and listing all relevant
bugs at a single place is a nice way to detect problems
quickly.
</p><p>These bugs pages are available via
</p><div class="informalexample"><pre class="programlisting">
http://blends.debian.org/BLEND/bugs
</pre></div><p>
where <span class="package">BLEND</span> has to be replaced by the name of the
Blend. Currently these pages are available for the Blends:
</p><div class="informalexample"><pre class="programlisting">
accessibility, edu, gis, junior, lex, med, science, debichem
</pre></div><p>
In short: If you want to help enhancing the quality of a
specific Blend go to its bug page and start working on the
bugs listed there.
</p></dd><dt><span class="term"><a class="ulink" href="http://packages.debian.org/" target="_top">Web search</a></span></dt><dd><p>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</p><p>
<em><span class="remark">FIXME: & is sometimes broken!!!
<a class="ulink" href="http://packages.debian.org/cgi-bin/search_packages.pl?keywords=med-&subword=1" target="_top">http://packages.debian.org/cgi-bin/search_packages.pl?keywords=med-&subword=1</a>
^^^^^
</span></em>
<a class="ulink" href="http://packages.debian.org/cgi-bin/search_packages.pl?keywords=med-&subword=1" target="_top">http://packages.debian.org/cgi-bin/search_packages.pl?keywords=med-&subword=1</a>
</p><p>
As a result you will get a list of all Debian Med packages.</p></dd><dt><span class="term"><a class="ulink" href="http://qa.debian.org/developer.php" target="_top">Package Tracking System</a></span></dt><dd><p>
The Package Tracking System is a really great tool that
provides essential information about packages. Most Debian
Pure Blends are using a mailing list address as Maintainer of
their key packages which includes the metapackages. This so
called team maintenance of packages is on one hand very handy
from a developers point of view on the other hand it enables
using the Package Tracking System to get a quick overview:
</p><div class="variablelist"><dl class="variablelist"><dt><span class="term">Debian Jr:</span></dt><dd><p>
<a class="ulink" href="http://qa.debian.org/developer.php?login=debian-jr@lists.debian.org" target="_top">http://qa.debian.org/developer.php?login=debian-jr@lists.debian.org</a>
</p></dd><dt><span class="term">Debian Med:</span></dt><dd><p>
<a class="ulink" href="http://qa.debian.org/developer.php?login=debian-med-packaging@lists.alioth.debian.org" target="_top">http://qa.debian.org/developer.php?login=debian-med-packaging@lists.alioth.debian.org</a>
</p></dd><dt><span class="term">Debian Edu:</span></dt><dd><p>
<a class="ulink" href="http://qa.debian.org/developer.php?login=debian-edu@lists.debian.org" target="_top">http://qa.debian.org/developer.php?login=debian-edu@lists.debian.org</a>
</p></dd><dt><span class="term">Debian Science:</span></dt><dd><p>
<a class="ulink" href="http://qa.debian.org/developer.php?login=debian-science-maintainers@lists.alioth.debian.org" target="_top">http://qa.debian.org/developer.php?login=debian-science-maintainers@lists.alioth.debian.org</a>
</p></dd></dl></div><p>
Hint: If you append the option <span class="package">&ordering=3</span> you
might get some sectioning of this page according to the
metapackage categories. This result is approached by a tool
which subscribes all dependent packages to the group
maintenance address and adds a section according to a
metapackage name.
</p><p>
The other way to use the Package Tracking System is to search
for packages starting with a certain letter:
</p><div class="variablelist"><dl class="variablelist"><dt><span class="term">Debian Jr:</span></dt><dd><p>
<a class="ulink" href="http://packages.qa.debian.org/j" target="_top">http://packages.qa.debian.org/j</a></p></dd><dt><span class="term">Debian Med:</span></dt><dd><p>
<a class="ulink" href="http://packages.qa.debian.org/m" target="_top">http://packages.qa.debian.org/m</a></p></dd></dl></div><p>
But the list that is obtained by this method is much larger
than it would be useful for a good overview.
</p></dd><dt><span class="term"><span class="package">list-junior.sh</span></span></dt><dd><p>The package <span class="package">junior-doc</span> contains a script
<code class="filename">/usr/share/doc/junior-doc/examples/scripts/list-junior.sh</code>
that checks for the installed packages of a Blend and builds
a simple web page describing these packages. (The BTS
contains a patch to let this script work also for other
Blends.)</p></dd></dl></div><p>
Short conclusion: <span class="emphasis"><em>The Debian Pure Blends provide some nice web
tools for a whole set of packages for a certain working field that
provide a better overview than the usual Debian tools that are
basically dealing with single packages..</em></span>
</p></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a name="future_handling"></a>6.2.5. Future handling of metapackages</h3></div></div></div><p>
Obviously there are no nifty tools as you might know them from Debian
available yet. The user interfaces for <span class="package">apt-get</span> 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 <span class="package">dpkg</span> to implement
reasonable functionality. The following items are target of future
development:
</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>Searching for existing metapackages</p></li><li class="listitem"><p>Overview about dependencies of these metapackages</p></li><li class="listitem"><p>Enhancing tools like <span class="package">aptitude</span>,
<span class="package">synaptic</span>, etc.</p></li><li class="listitem"><p>Special <span class="package">tasksel</span> section</p></li><li class="listitem"><p>Web tools that keep metapackage information up to
date</p></li></ul></div><p>
</p><p>
Furthermore it is necessary to find a set of keywords for each Debian
Pure Blend 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.
</p><p>
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.
</p></div></div><div class="sect1"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="userroles"></a>6.3. User roles</h2></div></div></div><p>
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.
</p><p>
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 Blend, which are
called "roles". There are several techniques available to manage user
roles. Currently in the field of Debian Pure Blends a UNIX group
based role system is implemented. This means, that a user who belongs
to a certain group of a Blend is mentioned in
the <code class="filename">/etc/group</code> file in the appropriate group and gets a
special user menu that is provided for exactly this group.
</p><p>
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
<span class="emphasis"><em>practical</em></span> limit to the number of groups to which a user may
belong for the existing Debian Pure Blends at this time.
</p><p>
In the long run, this role system might even be enhanced to certain
"<span class="emphasis"><em>levels</em></span>" 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 Debian Pure Blends but might
be interesting for Debian in general.
</p><p>
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.
</p><p>
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.
</p><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a name="menu_tools"></a>6.3.1. User menu tools</h3></div></div></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a name="user-menus"></a>6.3.1.1. Using the Debian menu system</h4></div></div></div><p>
The Debian menu system cares for menu updates after each package
installation. To enable compliance with the <span class="emphasis"><em>role</em></span> 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
<span class="citerefentry"><span class="refentrytitle">blend-update-menus</span>(8)</span> (see
<a class="xref" href="apa.html#blend-update-menus" title="A.2.2. blend-update-menus(8)">Section A.2.2, “<span class="citerefentry"><span class="refentrytitle">blend-update-menus</span>(8)</span>”</a>) script from
<span class="package">blends-common</span>. It has to be said that using
<span class="orgname">blend-update-menus</span> is not enough to change the menu of a
user. To accomplish this a call of the general
<span class="orgname">update-menu</span> script for every single user of a Blend is
necessary if this is not done by the
<code class="filename">postinst</code> script of a metapackage. This can easily been
done if the configuration file of a Debian Pure Blend
<code class="filename">/etc/blends/</code><code class="varname"><blend></code>/<code class="varname"><blend></code><code class="filename">.conf</code> contains the
line
</p><div class="informalexample"><pre class="programlisting">
UPDATEUSERMENU=yes
</pre></div><p>
</p><p>
It is strongly suggested to use the
package <span class="package">blends-dev</span> to build metapackages of a
Debian Pure Blend that will move all necessary files right into place
if there exists a
<code class="filename">menu</code> directory with the menu entries. Note, that the users
<code class="filename">${HOME}/.menu</code> directory remains untouched.
</p></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a name="user-debconf"></a>6.3.1.2. Managing Debian Pure Blend users with <span class="orgname">debconf</span></h4></div></div></div><p>
Using <span class="package">blends-dev</span> it is very easy to build a
<code class="varname">blend</code><span class="package">-config</span> package that contains
<span class="orgname">debconf</span> scripts to configure system users who should
belong to the group of users of the Debian Pure Blend <code class="varname">blend</code>.
For example see the <span class="package">med-common</span> package.
</p><div class="informalexample"><pre class="programlisting">
~> 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
</pre></div><p>
This example shows the situation when you
<span class="package">dpkg-reconfigure</span> <span class="package">med-common</span> if
<code class="varname">med user B</code> and <code class="varname">med user H</code> were defined as users
of Debian Med previously and <code class="varname">med user F</code> should be added to
the group of medical staff. (For sure it is more convenient to use the
more comfortable interfaces to <span class="package">debconf</span> but the used
SGML DTD <a class="ulink" href="http://bugs.debian.org/140684" target="_top">does not yet
support screen shots</a>.)
</p></div></div></div><div class="sect1"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="devtools"></a>6.4. Development tools</h2></div></div></div><p>
Building a metapackage is more or less equal for each meta
package. This was the reason to build a common source package
<span class="package">blend</span> that builds into two binary packages
</p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><span class="package">blends-dev</span></span></dt><dd><p>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.</p><p>This package is described in detail in appendix <a class="xref" href="apa.html#blends-dev" title="A.1. Package blends-dev">Section A.1, “Package <span class="package">blends-dev</span>”</a>.</p></dd><dt><span class="term"><span class="package">blends-common</span></span></dt><dd><p>This package provides some files that are common to meta
packages of Debian Pure Blends especially those that were
built using the tools of the package
<span class="package">blends-dev</span>. It introduces a method to handle
system users in a group named according to the name of the
Blend. The user menu approach is explained in detail
in <a class="xref" href="ch06.html#userroles" title="6.3. User roles">Section 6.3, “User roles”</a>.</p><p>This package is described in detail in appendix <a class="xref" href="apa.html#blends-common" title="A.2. Package blends-common">Section A.2, “Package <span class="package">blends-common</span>”</a>.</p></dd></dl></div><p>
The usage of the tools that are contained in these packages are
described now in detail.
</p></div><div class="sect1"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="namespace"></a>6.5. Dealing with name space pollution</h2></div></div></div><p>
Due to the fact that Blends might deal with quite specialised software
the user base is often quite small. In such use cases it happens that
some programs are using names that are used by other more frequently
used tools. For instance the Debian Med program <span class="package">plink</span>
has the same name as the program <code class="filename">plink</code> that belongs
to the ssh clone <span class="package">putty</span>. According to the Debian policy
both packages, <span class="package">putty</span> and <span class="package">plink</span> need
to be co-installable. Thus one tool has to be renamed.
</p><p>
Name space conflicts in Debian are usually solved by the principle that
whoever comes first has taken the name if there is no better agreement.
However, it makes sense to keep the original name chosen by upstream
for the more frequently used program - and here it might be that the
Blends packager steps back. There might be a chance to discuss with
upstream about a better name but there is no guarantee that this will be
successfully and thus there is another option for the Blends developer
to provide the original upstream name to the Blends users by circumventing
the file name conflict - at least for users of the <code class="filename">bash</code>
shell.
</p><p>
Since <span class="package">blends-dev >= 0.6.92.3</span> in the
<code class="varname">blend</code><span class="package">-config</span> a <code class="filename">bash</code>
init script is provided in
</p><div class="informalexample"><pre class="programlisting">
/etc/profile.d/<code class="varname"><BLEND-name></code>.sh
</pre></div><p>
This script is executed in login shells and checks for two things:
</p><p>
</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>
Does the path <code class="filename">/usr/lib/<code class="varname"><BLEND-name></code>/bin</code>
exist (since a package installs files there)?
</p></li><li class="listitem"><p>
Has the user starting the <code class="filename">bash</code> instance created a file
<code class="filename">$HOME/.blends</code> and is there a line featuring the name
of the Blend (in the example above "debian-med")
</p></li></ol></div><p>
</p><p>
If both conditions are fulfilled the PATH gets prepended by
<code class="filename">/usr/lib/<code class="varname"><BLEND-name></code>/bin</code>
and thus the tools residing in this directory were found first.
</p><p>
Moreover also MANPATH is prepended by
<code class="filename">/usr/lib/<code class="varname"><BLEND-name></code>/share/man</code>
to enable providing proper manpages to the binaries in the Blends private
PATH. Otherwise it might happen that a user might see a manpage of the
executable in <code class="filename">/usr/bin</code> which is not the first in the
search PATH any more. The location is a topic of further discussion since
manpages under <code class="filename">/usr/lib</code> are in conflict with FHS.
</p></div></div><div class="navfooter"><hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="ch05.html">Prev</a> </td><td width="20%" align="center"> </td><td width="40%" align="right"> <a accesskey="n" href="ch07.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Chapter 5. Distributions inside Debian </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> Chapter 7. How to start a Debian Pure Blend</td></tr></table></div></body></html>
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