yadifad: 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/yadifad - from package: yadifa

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

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