cracker: 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 CentOS possible default full paths are:

/usr/libexec/crack/bin/cracker - from package: crack

You may install the required package with command yum install {package}

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