mrd6: 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/sbin/mrd6 - from package: mrd6

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

Error in other languages:
mrd6: bevel nie gevind nie
mrd6: comandă negăsită
mrd6: comando não encontrado
mrd6: commande introuvable
mrd6: command not found
mrd6: käsku ei ole
mrd6: không tìm thấy lệnh
mrd6: komanda nerasta
mrd6: Kommando nicht gefunden.
mrd6: kommandot finns inte
mrd6: komut yok
mrd6: nie znaleziono polecenia
mrd6: níor aimsíodh an t-ordú
mrd6: no se encontró la orden
mrd6: no s'ha trobat l'ordre
mrd6: opdracht niet gevonden
mrd6: parancs nem található
mrd6: perintah tidak ditemukan
mrd6: príkaz nenájdený
mrd6: příkaz nenalezen
mrd6: команда не найдена
mrd6: командата не е открита
mrd6: 命令找不到
mrd6: コマンドが見つかりません