So currently I have firebird 2.5 installed and running on Windows, working fine but performance is a bit slow.

I have installed 2.5 on Ubuntu, and I can connect to the current database with ISQL easily:

connect "192.168.155.112:C:\database\database.FDB" user 'SYSDBA' password 'adminpassword';

So I stopped the firebird services on the Windows server, copied the file to the Ubuntu server, and in isql tried to run:

SQL> connect "localhost:/var/lib/firebird/2.5/data/database.FDB" user 'SYSDBA' password 'adminpassword';
Statement failed, SQLSTATE = m
file /var/lib/firebird/2.5/data/database.FDB is not a valid database

Note I have so far tried:

~$ sudo adduser `id -un` firebird
[sudo] password for luke:
The user `luke' is already a member of `firebird'.

As well as

# chown firebird /var/lib/firebird/2.5/data/database.fdb

With no luck, if anyone has any idea as to why I might be getting this error, I would be very grateful :)

I am not sure if Super or Classic was used on Windows, however I have tried using both on Ubuntu with the same error message. Windows server version 2.5.6, same version on Linux