fdk: 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/fdk - from package: plastimatch

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

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