ddns-confgen: 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/ddns-confgen - from package: bind

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

On Debian possible default full paths are:

/usr/sbin/ddns-confgen - from package: bind9

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

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