def2a: 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/def2a - from package: alliance

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

Error in other languages:
def2a: bevel nie gevind nie
def2a: comandă negăsită
def2a: comando não encontrado
def2a: commande introuvable
def2a: command not found
def2a: käsku ei ole
def2a: không tìm thấy lệnh
def2a: komanda nerasta
def2a: Kommando nicht gefunden.
def2a: kommandot finns inte
def2a: komut yok
def2a: nie znaleziono polecenia
def2a: níor aimsíodh an t-ordú
def2a: no se encontró la orden
def2a: no s'ha trobat l'ordre
def2a: opdracht niet gevonden
def2a: parancs nem található
def2a: perintah tidak ditemukan
def2a: príkaz nenájdený
def2a: příkaz nenalezen
def2a: команда не найдена
def2a: командата не е открита
def2a: 命令找不到
def2a: コマンドが見つかりません