sisu5: 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/sisu5 - from package: sisu

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

Error in other languages:
sisu5: bevel nie gevind nie
sisu5: comandă negăsită
sisu5: comando não encontrado
sisu5: commande introuvable
sisu5: command not found
sisu5: käsku ei ole
sisu5: không tìm thấy lệnh
sisu5: komanda nerasta
sisu5: Kommando nicht gefunden.
sisu5: kommandot finns inte
sisu5: komut yok
sisu5: nie znaleziono polecenia
sisu5: níor aimsíodh an t-ordú
sisu5: no se encontró la orden
sisu5: no s'ha trobat l'ordre
sisu5: opdracht niet gevonden
sisu5: parancs nem található
sisu5: perintah tidak ditemukan
sisu5: príkaz nenájdený
sisu5: příkaz nenalezen
sisu5: команда не найдена
sisu5: командата не е открита
sisu5: 命令找不到
sisu5: コマンドが見つかりません