rng: 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/rng - from package: reportbug-ng

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

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