fbsvcmgr: 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/fbsvcmgr - from package: firebird

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

On Debian possible default full paths are:

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

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

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