Can not start the oracle enterprise manager

I am new to oracle and also new to linux.
With the help of lots of people i manages somehow to install 10g on debian.

But now I can not start the enterprise manager.

neinstein@han:~$ su - oracle
Password:
oracle@han:~$ emctl start dbconsole
TZ set to Europe/Berlin
Environment variable ORACLE_SID not defined. Please define it.
oracle@han:~$

I added the following line in /home/oracle/.bash_profile
export ORACLE_SID=mydb

then I entered this again: emclt start dbconsole

oracle@han:~$ emctl start dbconsole
TZ set to Europe/Berlin
OC4J Configuration issue. /home/oracle/product/10.1.0/Db_1/oc4j/j2ee/OC4J_DBConsole_localhost.localdomain_mydb not found.
oracle@han:~$

Now what do i do? I am stuck following this tutorial:
http://www.oracle.com/technology/obe/2day_dba/gettingstarted/gettingstarted.htm