Instalação firebird 3.0 (Ubuntu 18.04 LTS)

adduser: The user `firebird' already exists, but is not a system user. Exiting.
dpkg: erro ao processar o pacote firebird3.0-server (--configure):
installed firebird3.0-server package post-installation script subprocess returned error exit status 1
A processar 'triggers' para ureadahead (0.100.0-20) ...
A processar 'triggers' para systemd (237-3ubuntu10.3) ...
Erros foram encontrados durante o processamento de:
firebird3.0-server
E: Sub-process /usr/bin/dpkg returned an error code (1)