sup: command not found

Have You tried accessing the binary with the full path?

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH

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/sup - from package: sup

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