cfn-hup: 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/cfn-hup - from package: heat-cfntools

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

On Debian possible default full paths are:

/usr/bin/cfn-hup - from package: heat-cfntools

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

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