gsec: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On CentOS possible default full paths are:

/usr/bin/gsec - from package: firebird

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/gsec - from package: firebird2.5-classic-common
/usr/bin/gsec - from package: firebird2.5-super

You may install the required package with command apt-get install {package}

Error in other languages:
gsec: bevel nie gevind nie
gsec: comandă negăsită
gsec: comando não encontrado
gsec: commande introuvable
gsec: command not found
gsec: käsku ei ole
gsec: không tìm thấy lệnh
gsec: komanda nerasta
gsec: Kommando nicht gefunden.
gsec: kommandot finns inte
gsec: komut yok
gsec: nie znaleziono polecenia
gsec: níor aimsíodh an t-ordú
gsec: no se encontró la orden
gsec: no s'ha trobat l'ordre
gsec: opdracht niet gevonden
gsec: parancs nem található
gsec: perintah tidak ditemukan
gsec: príkaz nenájdený
gsec: příkaz nenalezen
gsec: команда не найдена
gsec: командата не е открита
gsec: 命令找不到
gsec: コマンドが見つかりません