/usr/lib/ is in firebird2.1-server-common 2.1.4.18393-0.ds2-6build1.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/firebird/
/usr/lib/firebird/2.1/
/usr/lib/firebird/2.1/UDF/
/usr/lib/firebird/2.1/UDF/fbudf.sql
/usr/lib/firebird/2.1/UDF/ib_udf.sql
/usr/lib/firebird/2.1/UDF/ib_udf2.sql
/usr/lib/firebird/2.1/bin/
/usr/lib/firebird/2.1/bin/qli
/usr/lib/firebird/2.1/bin/nbackup
/usr/lib/firebird/2.1/bin/isql
/usr/lib/firebird/2.1/bin/gsec
/usr/lib/firebird/2.1/bin/gfix
/usr/lib/firebird/2.1/bin/gdef
/usr/lib/firebird/2.1/bin/gbak
/usr/lib/firebird/2.1/bin/gstat
/usr/lib/firebird/2.1/security2.fdb
/usr/lib/firebird/2.1/run
/usr/lib/firebird/2.1/firebird.log
/usr/lib/firebird/2.1/aliases.conf
/usr/lib/firebird/2.1/help