sisu-txt: 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/sisu-txt - from package: sisu

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

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