окно #1 
$ /opt/fb30trnk/bin/isql localhost/3333:/var/db/fb30/production30.fdb
Database:  localhost/3333:/var/db/fb30/production30.fdb
SQL> create user nikto password 'nikak';
SQL> commit;
SQL> revoke all on all from nikto;
Statement failed, SQLSTATE = 00000
Warning: ALL on ALL is not granted to NIKTO.
Warning: ALL on ALL is not granted to NIKTO.
SQL> quit;

$ /opt/fb30trnk/bin/isql /var/db/fb30/production30.fdb -user nikto -pas nikak
Database:  /var/db/fb30/production30.fdb, User: nikto
SQL> set list on;
SQL> select current_user,current_role from rdb$database;

USER                            NIKTO
ROLE                            NONE

SQL> commit;

 окно #2 
/opt/fb30trnk/bin/gfix -shut single -force 0 /var/db/fb30/production30.fdb
I/O error during "lock" operation for file "/var/db/fb30/production30.fdb"
-Error while trying to open file
-Resource temporarily unavailable
/opt/fb30trnk/bin/gstat -h /var/db/fb30/production30.fdb | grep -i 'attributes\|production30.fdb'
Database "/var/db/fb30/production30.fdb"
        Attributes -- пусто, нет фразы 'shutdown' или 'single'

ISQL Version: LI-T3.0.0.30889 Firebird 3.0 Alpha 2
Server version:
Firebird/Linux/AMD/Intel/x64 (access method), version "LI-T3.0.0.30889 Firebird 3.0 Alpha 2"
on disk structure version 12.0