Oracle Database Discussions

I installed Oracle DB 11g on Linux.
When the installation completed, I was able to create a new DB (using the DBCA tool), and connect to it from a client (Navicat).

I did however reboot my system, and now, nothing is started, I can't figure out how to start all of it.
The dbstart tool runs for 1 second (I gave it my ORACLE_BASE), starting some process that listens on port 1521, that's all.

Before the reboot, 1GB of RAM was used for the Oracle DB , now 5 MB, just for the tnslsnr.

My client tells me the listener doesn't know my SID. The DBCA tool also no longer wants to start.

What is it that I'm doing wrong? Thanks for helping out a starter!