Netkernel comes with HSQLDB as its onboard small database.
There are however several other posibilities for small "no fuss" databases.
My personal favorite one is sqlite.

In order to get sqlite working from within Netkernel you first need the
SQLite JDBC driver. You can find it on http://www.zentus.com/sqlitejdbc/
I've found tested the "Pure Java" one. Drop the jar
(sqlitejdbc-v037-nested at this moment) into the lib directory of your
application (for example in modules\workbench\lib if you want it available
in all the workbench applications.

Reboot Netkernel.

What remains is your configRDBMS.xml which looks like this :

<config>   <rdbms>     <jdbcDriver>org.sqlite.JDBC</jdbcDriver>     <jdbcConnection>jdbc:sqlite:/db/test.db</jdbcConnection>   </rdbms> </config>

Didnt I say "no fuss" ? Sqlite has no concept of users or all of that :-). But
it does comply with the SQL standards.

Enjoy.
Gynwer