ldnsd: 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/ldnsd - from package: ldns

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

On Debian possible default full paths are:

/usr/bin/ldnsd - from package: ldnsutils

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

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