discus: 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/discus - from package: discus

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

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