cf-key: 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/sbin/cf-key - from package: cfengine

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

On Debian possible default full paths are:

/usr/sbin/cf-key - from package: cfengine3
/usr/lib/debug/usr/sbin/cf-key - from package: cfengine3-dbg

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

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