Installing Firebird on Debian (Jessie in my case) gave a problem: after installing and starting the server I was not able to connect to the database server:
Your user name and password are not defined. Ask your database administrator to set up a Firebird login.
using the sysdba password I entered in the installation dialog.
Unfortunately it seems the installation procedure has a bug, and does not accept the entered password, but attributes a random password. This random password can you find in the file
The connect with this random password succeedes and you can change your password afterwards – but you must change it with both the Firebird administration tools and inside this file.
The password can be changed with the gsec tool:
gsec -user sysdba -password <password_from_SYSDBA.password>
modify sysdba -pw <your_new_password>
And another speciality for Debian:
The isql tool is called isql-fb