>    One question related to changing SYSDBA password for the

first time without using gsec.

>    I noticed that, as you have no other database than

security3.fdb, you must connect to it,

>    but for doing so you can't

use remote connections ( not even localhost )

  Correct

>    and, as you access directly to the database file, you must run isql-fb as root.

  Why do you think so ? You should be member of "firebird" group, created by installer.

No need to be a root. Never.