mcookie: 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/bin/mcookie - from package: util-linux-ng

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

On Debian possible default full paths are:

/usr/bin/mcookie - from package: util-linux

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

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