Oracle Express 10g Installation Ubuntu

Otherwise OS/APP is not supported, is a good scenario for testing purposes
Basic steps:

ocm@achtung:~$ sudo dpkg -i oracle-xe_10.2.0.1-1.0_i386.deb
....boring... not remarkable...
ocm@achtung:~$ **sudo /etc/init.d/oracle-xe configure**

Oracle Database 10g Express Edition Configuration
-------------------------------------------------
This will configure on-boot properties of Oracle Database 10g Express
Edition.  The following questions will determine whether the database should
be starting upon system boot, the ports it will use, and the passwords that
will be used for database accounts.  Press <Enter> to accept the defaults.
Ctrl-C will abort.

Specify the HTTP port that will be used for Oracle Application Express [8080]:

Note if you dont want to enable the http admin acccess you can set to 0 now or later, which disables this feature. We assigned to 8888 for showing later how to disable.
We continue:
Specify a port that will be used for the database listener [1521]:

Specify a password to be used for database accounts.  Note that the same
password will be used for SYS and SYSTEM.  Oracle recommends the use of
different passwords for each database account.  This can be done after
initial configuration:
Confirm the password:

Do you want Oracle Database 10g Express Edition to be started on boot (y/n) [y]:n

Starting Oracle Net Listener...Done
Configuring Database...Done
Starting Oracle Database 10g Express Edition Instance...Done
Installation Completed Successfully.
To access the Database Home Page go to "http://127.0.0.1:8888/apex"

We asign also the default 1521 for listener, and disable init at boot.
Lets try to login using sqlplus:
ocm@achtung:~$ sqlplus SYS/password@localhost:1521/XE as SYSDBA
SQL*Plus: Release 10.2.0.1.0 - Production on Tue Mar 13 16:12:58 2012
Copyright (c) 1982, 2005, Oracle.  All rights reserved.

Connected to:
Oracle Database 10g Express Edition Release 10.2.0.1.0 - Production
SQL>

Maybe is a good moment to give a look at securing-oracle
After done, you can Oracle manage users