I have just installed koha 3016.04 on ubuntu 12.04. But after creating staff patron I am unable to log in.

If by "created a staff patron" you mean "created a patron using the 'staff' patron category," that is not sufficient to allow access to the staff client. You'll need to log in as the database administrator and set the appropriate permissions for that patron: http://manual.koha-community.org/3.16/en/patronpermissions.html -- Owen -- Web Developer Athens County Public Libraries http://www.myacpl.org