firmdl3: 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 Debian possible default full paths are:

/usr/bin/firmdl3 - from package: brickos

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

Error in other languages:
firmdl3: bevel nie gevind nie
firmdl3: comandă negăsită
firmdl3: comando não encontrado
firmdl3: commande introuvable
firmdl3: command not found
firmdl3: käsku ei ole
firmdl3: không tìm thấy lệnh
firmdl3: komanda nerasta
firmdl3: Kommando nicht gefunden.
firmdl3: kommandot finns inte
firmdl3: komut yok
firmdl3: nie znaleziono polecenia
firmdl3: níor aimsíodh an t-ordú
firmdl3: no se encontró la orden
firmdl3: no s'ha trobat l'ordre
firmdl3: opdracht niet gevonden
firmdl3: parancs nem található
firmdl3: perintah tidak ditemukan
firmdl3: príkaz nenájdený
firmdl3: příkaz nenalezen
firmdl3: команда не найдена
firmdl3: командата не е открита
firmdl3: 命令找不到
firmdl3: コマンドが見つかりません