rt-app: 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/rt-app - from package: rt-app

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

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