hadd: 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/hadd - from package: root

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

On Debian possible default full paths are:

/usr/bin/hadd - from package: root-system-bin

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

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