arara: 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/arara - from package: texlive-extra-utils

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

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