On Debian based systems (Debian, Ubuntu, Univention Corporate Server),
database configuration can be done with help of the dbconfig system.

  * Package: dbconfig-common
  * Documentation: https://www.debian.org/doc/manuals/dbconfig-common/

Install/update scenarios:
  * fresh install
  * preinstalled 2001
  * preinstalled 2002
  * 12: 2001 -> 2002, 13: 2001 -> 2002: update from 12 to 13

Behavior:
  * config file: /etc/dbconfig-common/bareos.conf
  * sql files stored at
    * /usr/share/dbconfig-common/data/bareos-database-common/upgrade/pgsql/2001
    * /usr/share/dbconfig-common/data/bareos-database-common/upgrade/pgsql/2002
    * /usr/share/dbconfig-common/data/bareos-database-common/install/pgsql

Upgrade:
  * bareos-database-common.postinst
    * every file from /usr/share/dbconfig-common/data/bareos-database-common/upgrade/DATABASE/*, that is larger than parameter $2 (package version of replaced package) will be installed.
        * even if the filename "is larger" than current package version
        * dbconfig does not store the installed version. It uses only the old and the current package version.
    * in Bareos, different branches can each do a database version update, example:
      * 12.4.6: 2001
      * 12.4.7: 2002
      * 12.4.8: 2003
      * 13.2.2: 2001
      * 13.2.3: 2002
      * 13.2.4: 2003
      * using standard dbconfig this could result in following
        * updating from 12.4.6 to 13.2.3 would result in a database update from
          * 2001 (12.4.6) -> 2002 (12.4.7) -> 2003 (12.4.8) -> 2001 (13.2.2) ... => failure
    * Bareos modifies the dbconfig behavior by not working with package versions, but database versions:
      * bareos-database-common.config, bareos-database-common.postinst:
        * instead of passing parameter $2 (old package version), this gots translated to database version with the help of a map file (versions.map).
           * with the help of this, every database schema update is only be done once
    * how to handle package update from version without dbconfig to version with it?
      Bareos dbconfig will be introduced with some version >= 14.1.0.
      The latest database version for 12.4 and 13.2 will be 2002.
      Therefore we claim, that the first version using db_config will be 2003, even if it is only 2002. Using this, all existing database updates get applied.
        if dpkg --compare-versions "$param2_orig" lt "14.1.0"; then
            dbc_first_version="2003"
            ...
        fi

Database Permissions by dbconfig:

PostgreSQL:
    bareos will be the database owner

Testing:
# bareos-database-dbconfig
#   ~/dbconf
#     fakeroot debian/rules binary
#  /var/lib/dpkg/info/*.postinst ...
/var/log/dbconfig-common/dbc.log

eval "`dbconfig-generate-include /etc/dbconfig-common/bareos-database-common.conf`"



Behavior
========

noninteractive
==============

export DEBIAN_FRONTEND=noninteractive
echo "bareos-database-common bareos-database-common/mysql/admin-pass select linuxlinux" | debconf-set-selections

postgresql
==========

  * install
    * /etc/dbconfig-common/bareos-database-common.conf created
    * db: setup
  * update from 12.4:
    * updates db_version from 2001 to 2002.
  * update from 13.2:
    * db_version is already 2002. It detects, nothing to do.
  * update dbconfig already configured
