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dbconfig-common
documentation
dbconfig-common
in your packages
there are three things you will have to do as a package maintainer if you want
to use dbconfig-common
: provide the database code/scripts to setup
the data base, source the maintainer script libraries and launch
dbconfig-common
. dbconfig-common
will take care of
everything else, include all debconf related questions, database/database-user
creation, upgrade/remove/purge logic, et c. after all, the goal of
dbconfig-common
is to make life easier for both the local admin
and the package maintainer :)
in the postinst, prerm, and postrm scripts for
your package, you will need to source the libraries which perform most of the
work for you (you do not need to do so in your preinst script). if
you are not currently using debconf in your package, you will be now, and the
debconf libraries need to be sourced first. you will need to depend on debconf
explicitly, and either use dh_installdebconf or otherwise install your
config script into your deb file if you're not already doing so.
for example, here's an what it should look like in a postinst script
for an imaginary foo-mysql
package:
#!/bin/sh # postinst maintainer script for foo-mysql # source debconf stuff . /usr/share/debconf/confmodule # source dbconfig-common stuff . /usr/share/dbconfig-common/dpkg/postinst.mysql dbc_go foo-mysql $@ # ... rest of your code ...
dbc_go is a function defined in every maintainer script hook to
execute the appropriate code based on which maintainer script is being run.
note that it is passed two arguments. foo-mysql
, the name of the
package (there's sadly no clean way to figure this out automatically), and
$@ (the arguments which were passed to the maintainer script).
note that if your package does not use debconf, you will need to explicitly
install the config script in your package. the easiest way to do so
is to call dh_installdebconf from debian/rules
. XXX: add a note
about how to ignore the lintian warnings about missing templates files.
There are three directories in which you can place code for installing the databases of your package:
/usr/share/dbconfig-common/data/PACKAGE/install/DBTYPE
/usr/share/dbconfig-common/data/PACKAGE/install-dbadmin/DBTYPE
/usr/share/dbconfig-common/scripts/PACKAGE/install/DBTYPE
where PACKAGE is the name of the package, DBTYPE is the type of data (mysql, postgresql, et c).
The first directory is for the majority of situations, in which the database can be constructed from it's native language (SQL for mysql/postgresql, for example). The data will be fed to the underlying database using the credentials of the database user. The second directory is like the first directory, but will be run using the credentials of the database administrator. Warning: use of this second directory should only be done when there are excerpts of database code that must be run as the database administrator (such as some language constructs in postgresql) and should otherwise be avoided. The third location is for databases that require a more robust solution, in which executable programs (shell/perl/python scripts, or anything else) can be placed.
This code will only be executed on new installs and reconfiguration of failed
installs. In the case of SQL databases, in the data directory you would find
the simple create and insert statements needed to create tables and populate
the database. You do not need to create the underlying database, only
populate it. The scripts directory contains shell/perl/python/whatever
scripts, which are passed the same arguments as dbc_go. If you need
database connection information (username, password, etc) in your scripts, you
can source the /bin/sh
format package config file, or you can
instruct dbconfig-common
to generate one in your programming
language of choice (see the advanced tips section).
if files exist in both data and scripts, they will both be executed in an unspecified order.
that's it! the rest of what needs to be done is handled by
dbconfig-common
, which should keep all the work (and bugs) in one
place. happy packaging! Of course, it's recommended you take a quick look
through the rest of the document, just to get an idea of other things that
dbconfig-common
can do for you in case you have special needs.
your database application will probably require a username and password in
order to function. every package that uses dbconfig-common
already has a /bin/sh includable format config file, but it may be more
convenient to have something in the native language of the package. for
example, packaging a php/mysql web app would be a lot easier if there were
already a file existing with all the information in php includable format.
using dbconfig-common
, you can do this with little effort. in
your postinst script, define the variable
dbc_generate_include to a value that follows the form
format:location where format is one of the supported
output formats of dbconfig-generate-include (list them with -h) and
location is the absolute location where you want your config file to go. there
are also some extra variables dbc_generate_include_owner,
dbc_generate_include_perms, and dbc_generate_include_args
which do what you would expect them to. note: you will be responsible for
removing this file in your postrm script. when your scripts
are run, this environment variable will be exported to your scripts, as well as
a variable dbc_config_include which has the same value, but with the
leading format: stripped away for convenience.
dbconfig-common
into an existing package
If your package is already part of debian, dbconfig-common
provides some support to load pre-existing settings from a specified config by
setting two variables: dbc_first_version and
dbc_load_include.
dbc_load_include should be specified in the config script and be of the format format:inputfile. format is one of the languages understood by dbconfig-load-include, and inputfile is either the config file in format language, or a script file in format language that otherwise determines the values and sets them.
dbc_first_version should be specified in both the config
and postinst scripts, and should contain the first version
in which dbconfig-common
was introduced. when the package is
installed, if it is being upgraded from a version less than this value it will
attempt to bootstrap itself with the values.
occassionaly, the upstream authors will modify the underlying databases between versions of their software. for example, in mysql applications column names may change, move to new tables, or the data itself may need to be modified in newer upstream versions of a package.
in order to cope with this, a second set of directories exists for providing packagers ways to modify the databases during package upgrades:
/usr/share/dbconfig-common/data/PACKAGE/upgrade/DBTYPE/VERSION
/usr/share/dbconfig-common/data/PACKAGE/upgrade-dbadmin/DBTYPE/VERSION
/usr/share/dbconfig-common/scripts/PACKAGE/upgrade/DBTYPE/VERSION
where VERSION is the version at which the upgrade should be applied.
when a package upgrade occurs, all instances of VERSION which are
newer than the previously installed version will be applied, in order. there
is also an automatically included set of safeguards and behaviour provided by
dbconfig-common
, so as the packager you shouldn't need to worry
about most of the error-handling.
as with installation, scripts will be passed the same cmdline arguments as were passed to dbc_go.
sometimes, a particular package may support multiple database types. this is common with perl or php based web applications, which frequently use some form of database abstraction layer (pear DB for php, the DBD family for perl).
dbconfig-common
provides support for such applications in a
relatively straightforward fashion, allowing the local admin to select which
database type to use when configuring a database for a package
to take advantage of this feature, you will want to use the "generic" maintainer script hooks, and additionally hint the debconf config script with the types of databases your package supports. for example, the postinst script would now look like this:
#!/bin/sh # postinst maintainer script for foo-mysql # source debconf stuff . /usr/share/debconf/confmodule # source dbconfig-common stuff . /usr/share/dbconfig-common/dpkg/postinst dbc_go foo-mysql $@ # ... rest of your code ...
The config script would contain an additional variable called "dbc_dbtypes", which is a comma-seperated list of supported database types:
#!/bin/sh # config maintainer script for foo-mysql # source debconf stuff . /usr/share/debconf/confmodule # we support mysql and pgsql dbc_dbtypes="mysql, pgsql" # source dbconfig-common stuff . /usr/share/dbconfig-common/dpkg/config dbc_go foo-mysql $@ # ... rest of your code ...
dbconfig-common
has a set of pre-defined default values for most
of the questions with which it prompts the user, most of which are variations
on the name of the package. however, as a packager you can override some these
values and set defaults that you feel are more appropriate, as well as
otherwise modify the behavior of some parts of dbconfig-common
.
the following table lists the variables you can hint in your config
script, as well as some other variables you can use to have a finer level of
control over dbconfig-common
. you must use these variables
exactly (and only) where directed in this table.
name to use when connecting to database (defaults to: package name)
name of database resource to which to connect (defaults to: package name)
database types supported by the package (defaults to: empty)
format:outputfile pair for an extra config to be generated by dbconfig-generate-include. (defaults to: empty)
set the owner:group of include files generated by dbconfig-generate-include (defaults to: empty)
set the permissions of include files generated by dbconfig-generate-include (defaults to: empty)
arguments passed directly to dbconfig-generate-include (defaults to: empty)
the first version in which dbconfig-common
was introduced in the
package (defaults to: empty)
format:includefile pair for a config to be read in by dbconfig-load-include (defaults to: empty)
arguments passed directly to dbconfig-load-include (defaults to: empty)
dbconfig-common
in the event that your package is having trouble working with
dbconfig-common
, the first thing you should try is to export and
set the shell variable dbc_debug to a nonempty value before
installing your package. this will provide a slightly larger amount of
information about what's going on.
in the event that this does not provide enough information, the next thing to
do will provide much, much, more information; enough that you will probably
want to redirect stderr into a temporary output file. in the file
/usr/share/dbconfig-common/dpkg/common
, uncomment the set
-x line near the top of the file. this will show you all the shell
commands and logic as they are executed. if you have a good idea of where the
problem is occurring, you can also insert your own set -x lines
elsewhere followed by set +x lines to reduce the amount of input.
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dbconfig-common
documentation