dfg2dfg: 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/dfg2dfg - from package: spass

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

Error in other languages:
dfg2dfg: bevel nie gevind nie
dfg2dfg: comandă negăsită
dfg2dfg: comando não encontrado
dfg2dfg: commande introuvable
dfg2dfg: command not found
dfg2dfg: käsku ei ole
dfg2dfg: không tìm thấy lệnh
dfg2dfg: komanda nerasta
dfg2dfg: Kommando nicht gefunden.
dfg2dfg: kommandot finns inte
dfg2dfg: komut yok
dfg2dfg: nie znaleziono polecenia
dfg2dfg: níor aimsíodh an t-ordú
dfg2dfg: no se encontró la orden
dfg2dfg: no s'ha trobat l'ordre
dfg2dfg: opdracht niet gevonden
dfg2dfg: parancs nem található
dfg2dfg: perintah tidak ditemukan
dfg2dfg: príkaz nenájdený
dfg2dfg: příkaz nenalezen
dfg2dfg: команда не найдена
dfg2dfg: командата не е открита
dfg2dfg: 命令找不到
dfg2dfg: コマンドが見つかりません