gdnsd: 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 Debian possible default full paths are:

/usr/sbin/gdnsd - from package: gdnsd

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

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