cfkey: 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/lib/debug/usr/sbin/cfkey - from package: cfengine2-dbg
/usr/sbin/cfkey - from package: cfengine2

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

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