ra: 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
/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/ra - from package: argus-client

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