dnsyo: 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/dnsyo - from package: dnsyo

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

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