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<chapter id="admin">
  <title>Kea Database Administration</title>

  <section id="kea-database-version">
    <title>Databases and Database Version Numbers</title>

    <para>
      Kea stores leases in one of several supported databases.
      As future versions of Kea are released, the structure of those
      databases will change. For example, Kea currently only stores
      lease information: in the future, additional data - such as host
      reservation details - will also be stored.
    </para>

    <para>
      A given version of Kea expects a particular structure in
      the database.  It ensures this by checking the version of the
      database it is using.  Separate version numbers are maintained for
      backend databases, independent of the version of Kea itself. It
      is possible that the backend database version will stay the same
      through several Kea revisions. Likewise, it is possible that the
      version of backend database may go up several revisions during a
      Kea upgrade.  Versions for each database are independent, so an
      increment in the MySQL database version does not imply an increment
      in that of PostgreSQL.
    </para>

    <para>
      Backend versions are specified in
      a <replaceable>major.minor</replaceable> format. The minor
      number is increased when there are backward compatibile changes
      introduced.  For example, the addition of a new index. It is
      desirable, but not mandatory to to apply such a change; you
      can run on older database version if you want to. (Although, in
      the example given, running without the new index may be at the
      expense of a performance penalty.) On the other hand, the major
      number is increased when an incompatible change is introduced,
      for example an extra column is added to a table. If you try to
      run Kea software on a database that is too old (as signified by
      mismatched backend major version number), Kea will refuse to run:
      administrative action will be required to upgrade the database.
    </para>
  </section>

  <section id="kea-admin">
    <title>The kea-admin Tool</title>

    <para>
      To manage the databases, Kea provides the
      <command>kea-admin</command> tool. It is able to initialize
      a new database, check its version number, and perform a
      database upgrade.
    </para>

    <para>
      <command>kea-admin</command> takes two mandatory
      parameters: <command>command</command> and
      <command>backend</command>. Additional, non-mandatory options
      may be specified. Currently supported commands are:

      <itemizedlist>
        <listitem>
          <simpara>
            <command>lease-init</command> &mdash;
            Initializes a new lease database. Useful during first
            Kea installation. The database is initialized to the
            latest version supported by the version of the software.
          </simpara>
        </listitem>

        <listitem>
          <simpara>
            <command>lease-version</command> &mdash;
            Reports the lease database version number. This is
            not necessarily equal to the Kea version number as
            each backend has its own versioning scheme.
          </simpara>
        </listitem>

        <listitem>
          <simpara>
            <command>lease-upgrade</command> &mdash;
            Conducts a lease database upgrade. This is useful when
            upgrading Kea.
          </simpara>
        </listitem>
      </itemizedlist>

      <command>backend</command> specifies the backend type. Currently
      supported types are:

      <itemizedlist>
        <listitem>
          <simpara>
            <command>memfile</command> &mdash; Lease information is
            stored on disk in a text file.
          </simpara>
        </listitem>

        <listitem>
          <simpara>
            <command>mysql</command> &mdash;
            Lease information is stored in a MySQL relational
            database.
          </simpara>
        </listitem>

        <listitem>
          <simpara>
            <command>pgsql</command> &mdash;
            Lease information is stored in a PostgreSQL relational
            database.
          </simpara>
        </listitem>
      </itemizedlist>

      Additional parameters may be needed, depending on your setup
      and specific operation: username, password and database name or
      the directory where specific files are located. See appropriate
      manual page for details (<command>man 8 kea-admin</command>).
    </para>
  </section>

  <section>
    <title>Supported Databases</title>

    <section>
      <title>memfile</title>

      <para>
        There are no special initialization steps necessary
        for the memfile backend.  During the first run, both
        <command>kea-dhcp4</command> and <command>kea-dhcp6</command>
        will create an empty lease file if one is not
        present. Necessary disk write permission is required.
      </para>
      <!-- @todo: document lease file upgrades once they are implemented in kea-admin -->
    </section>

    <section>
      <title>MySQL</title>

      <para>
        The MySQL database must be properly set up if you want Kea to
        store information in MySQL. This section can be safely ignored
        if you chose to store the data in other backends.
      </para>


      <section id="mysql-database-create">
        <title>First Time Creation of Kea Database</title>

        <para>
          If you are setting the MySQL database for the first time,
          you need to create the database area within MySQL and set up
          the MySQL user ID under which Kea will access the database.
          This needs to be done manually: <command>kea-admin</command>
          is not able to do this for you.
        </para>

        <para>
          To create the database:

          <orderedlist>
            <listitem>
              <para>
                Log into MySQL as "root":
<screen>
$ <userinput>mysql -u root -p</userinput>
Enter password:
mysql>
</screen>
              </para>
            </listitem>

            <listitem>
              <para>
                Create the MySQL database:
<screen>
mysql> <userinput>CREATE DATABASE <replaceable>database-name</replaceable>;</userinput>
</screen>
                (<replaceable>database-name</replaceable> is the name
                you have chosen for the database.)
              </para>
            </listitem>

            <listitem>
              <para>
                Create the user under which Kea will access the database
                (and give it a password), then grant it access to the
                database tables:
<screen>
mysql> <userinput>CREATE USER '<replaceable>user-name</replaceable>'@'localhost' IDENTIFIED BY '<replaceable>password</replaceable>';</userinput>
mysql> <userinput>GRANT ALL ON <replaceable>database-name</replaceable>.* TO '<replaceable>user-name</replaceable>'@'localhost';</userinput>
</screen>
                (<replaceable>user-name</replaceable> and
                <replaceable>password</replaceable> are the user ID
                and password you are using to allow Keas access to the
                MySQL instance. All apostrophes in the command lines
                above are required.)
              </para>
            </listitem>

            <listitem>
              <para>
                At this point, you may elect to create the database
                tables. (Alternatively, you can exit MySQL and create
                the tables using the <command>kea-admin</command> tool,
                as explained below.)  To do this:
<screen>
mysql> <userinput>CONNECT <replaceable>database-name</replaceable>;</userinput>
mysql> <userinput>SOURCE <replaceable>path-to-kea</replaceable>/share/kea/scripts/mysql/dhcpdb_create.mysql</userinput>
</screen>
                (<replaceable>path-to-kea</replaceable> is the
                location where you installed Kea.)
              </para>
            </listitem>

            <listitem>
              <para>
                Exit MySQL:
<screen>
mysql> <userinput>quit</userinput>
Bye
$
</screen>
              </para>
            </listitem>
          </orderedlist>
        </para>

        <para>
          If you elected not to create the tables in step 4, you can do
          so now by running the <command>kea-admin</command> tool:
<screen>
$ <userinput>kea-admin lease-init mysql -u <replaceable>database-user</replaceable> -p <replaceable>database-password</replaceable> -n <replaceable>database-name</replaceable></userinput>
</screen>
          (Do not do this if you did create the tables in step 4.)
          <command>kea-admin</command> implements rudimentary checks:
          it will refuse to initialize a database that contains any
          existing tables. If you want to start from scratch, you
          must remove all data manually. (This process is a manual
          operation on purpose to avoid possibly irretrievable mistakes
          by <command>kea-admin</command>.)
        </para>
      </section>

      <section id="mysql-upgrade">
        <title>Upgrading a MySQL Database from an Earlier Version of Kea</title>

        <para>
          Sometimes a new Kea version may use newer database schema, so
          there will be a need to upgrade the existing database. This can
          be done using the <command>kea-admin lease-upgrade</command>
          command.
        </para>

        <para>
          To check the current version of the database, use the following command:
<screen>
$ <userinput>kea-admin lease-version mysql -u <replaceable>database-user</replaceable> -p <replaceable>database-password</replaceable> -n <replaceable>database-name</replaceable></userinput>
</screen>
          (See <xref linkend="kea-database-version"/> for a discussion
          about versioning.)  If the version does not match the minimum
          required for the new version of Kea (as described in the
          release notes), the database needs to be upgraded.
        </para>

        <para>
          Before upgrading, please make sure that the database is
          backed up.  The upgrade process does not discard any data but,
          depending on the nature of the changes, it may be impossible
          to subsequently downgrade to an earlier version.  To perform
          an upgrade, issue the following command:
<screen>
$ <userinput>kea-admin lease-upgrade mysql -u <replaceable>database-user</replaceable> -p <replaceable>database-password</replaceable> -n <replaceable>database-name</replaceable></userinput>
</screen>
        </para>
      </section>
    </section> <!-- end of MySQL sections -->

    <section>
      <title>PostgreSQL</title>

      <para>
        A PostgreSQL database must be set up if you want Kea to store
        lease and other information in PostgreSQL. This step can be
        safely ignored if you are using other database backends.
      </para>

      <section id="pgsql-database-create">
        <title>Manually Create the PostgreSQL Database and the Kea User</title>

        <para>
          The first task is to create both the lease database and the
          user under which the servers will access it. A number of steps
          are required:

          <orderedlist>
            <listitem>
              <para>
                Log into PostgreSQL as "root":
<screen>
$ <userinput>sudo -u postgres psql postgres</userinput>
Enter password:
postgres=#
</screen>
              </para>
            </listitem>

            <listitem>
              <para>
                Create the database:
<screen>
postgres=#<userinput> CREATE DATABASE <replaceable>database-name</replaceable>;</userinput>
CREATE DATABASE
postgres=#
</screen>
                (<replaceable>database-name</replaceable> is the name
                you have chosen for the database.)
              </para>
            </listitem>

            <listitem>
              <para>
                Create the user under which Kea will access the database
                (and give it a password), then grant it access to the
                database:
<screen>
postgres=#<userinput> CREATE USER <replaceable>user-name</replaceable> WITH PASSWORD '<replaceable>password</replaceable>';</userinput>
CREATE ROLE
postgres=#
postgres=#<userinput> GRANT ALL PRIVILEGES ON DATABASE <replaceable>database-name</replaceable> TO <replaceable>user-name</replaceable>;</userinput>
GRANT
postgres=#
</screen>
              </para>
            </listitem>

            <listitem>
              <para>
                Exit PostgreSQL:
<screen>
postgres=# <userinput>\q</userinput>
Bye
$
</screen>
              </para>
            </listitem>

            <listitem>
              <para>
                Create the database tables using the new user's
                credentials and the dhcpdb_create.pgsql script supplied
                with Kea.  After entering the following command, you
                will be prompted for the new user's password. When the
                command completes you will be returned to the shell
                prompt. You should see output similar to following:
<screen>
$ <userinput>psql -d <replaceable>database-name</replaceable> -U <replaceable>user-name</replaceable> -f <replaceable>path-to-kea</replaceable>/share/kea/scripts/pgsql/dhcpdb_create.pgsql</userinput>
Password for user <replaceable>user-name</replaceable>:
CREATE TABLE
CREATE INDEX
CREATE INDEX
CREATE TABLE
CREATE INDEX
CREATE TABLE
START TRANSACTION
INSERT 0 1
INSERT 0 1
INSERT 0 1
COMMIT
CREATE TABLE
START TRANSACTION
INSERT 0 1
COMMIT
$
</screen>
                (<replaceable>path-to-kea</replaceable> is the location
                where you installed Kea.)
              </para>

              <para>
                If instead you encounter an error like:
<screen>
psql: FATAL:  no pg_hba.conf entry for host "[local]", user "<replaceable>user-name</replaceable>", database "<replaceable>database-name</replaceable>", SSL off
</screen>
                ... you will need to alter the PostgreSQL configuration.
                Kea uses password authentication when connecting to
                the database and must have the appropriate entries
                added to PostgreSQL's pg_hba.conf file.  This file is
                normally located in the primary data directory for your
                PostgreSQL server. The precise path may vary but the
                default location for PostgreSQL 9.3 on Centos 6.5 is:
                <filename>/var/lib/pgsql/9.3/data/pg_hba.conf</filename>.
              </para>

              <para>
                Assuming Kea is running on the same host as PostgreSQL,
                adding lines similar to following should be sufficient to
                provide password-authenticated access to Kea's database:
<screen>
local   <replaceable>database-name</replaceable>    <replaceable>user-name</replaceable>                                 password
host    <replaceable>database-name</replaceable>    <replaceable>user-name</replaceable>          127.0.0.1/32           password
host    <replaceable>database-name</replaceable>    <replaceable>user-name</replaceable>          ::1/128                password
</screen>
              </para>

              <para>
                Please consult your PostgreSQL user manual before making
                these changes as they may expose your other databases
                that you run on the same system.
              </para>
            </listitem>
          </orderedlist>
        </para>
      </section>

      <section>
        <title>Initialize the PostgreSQL Database Using kea-admin</title>

        <para>
          Support for PostgreSQL in <command>kea-admin</command> is
          currently not implemented.
        </para>
        <!-- @todo: document PgSQL upgrade once they are implemented in kea-admin -->
      </section>
    </section> <!-- end of PostgreSQL sections -->
    <section>
      <title>Limitations related to the use of the SQL databases</title>

      <para>
        The lease expiration time is stored in the SQL database for each lease
        as a timestamp value. Kea developers observed that MySQL database doesn't
        accept timestamps beyond 2147483647 seconds (maximum signed 32-bit number)
        from the beginning of the epoch. At the same time, some versions of PostgreSQL
        do accept greater values but the value is altered when it is read back.
        For this reason the lease database backends put the restriction for the
        maximum timestamp to be stored in the database, which is equal to the
        maximum signed 32-bit number. This effectively means that the current
        Kea version can't store the leases which expiration time is later than
        2147483647 seconds since the beginning of the epoch (around year 2038).
      </para>
    </section>
  </section> <!-- End of Database sections -->

</chapter>
