ara: 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/ara - from package: ara

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