Once Oracle XE has been installed, and /etc/init.d/oracle-xe configure executed, I had some problems connecting the database, namely: ORA-12528: TNS:listener: all appropriate instances are blocking new connections. In my case, I did:
chown oracle:dba /usr/lib/oracle/xe/app/oracle/product/10.2.0/server/dbs /etc/init.d/oracle-xe stop su oracle export PATH=$PATH:$ORACLE_HOME/bin createdb.sh
This destroys the database created with /etc/init.d/oracle-xe configure, and creates a new one, with oracle as the password for the SYS and SYSTEM users. After exiting to root, and starting Oracle, now the management application listens correctly on the vserver IP address, and I can connect to the database with sqlplus. Meanwhile, the email for the confirmation of registration for the Oracle XE forum is still not arrived.
