I am trying to convert some programs that were originally written for
Interbase (and are still used with Interbase). The programs connect to a
local database (in a directory of the local user), process millions of
records in a single transaction, and disconnect. I am using Firebird 2.1
on Ubuntu and can connect just fine with qli and isql using no password
or user. But when I try running the converted programs the connection is
refused with the message:

ISC STATUS:
-Your user name and password are not defined. Ask your database
administrator to set up a Firebird login.
Terminating...

Where can I find information about how connections to firebird databases
are authenticated?