rarcrack: 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/rarcrack - from package: rarcrack

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

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