Or alternatively just issue sudo usermod -aG netdev oracle using an administrative account, in your case tsegay. You can set this in System tools > Users and Groups > oracle > Advanced Settings > User Privileges > Connect to wireless and ethernet networks. If the listener status is still not OK, ensure that the oracle user is a member of a network-allowed group, in case of Lubuntu it's the group netdev. It's better to permanently keep those 3 exports in oracle's.
ORACLE 10G INSTALLATION ON LINUX INSTALL
After installing I tried to start it with the command below.
I have installed oracle 10g on a ubuntu 10.x, This is my first time installation.