debian: 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:

/var/lib/Crack/bin/debian - from package: crack-md5
/var/lib/Crack/bin/debian - from package: crack

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

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