nsd-control: 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/nsd-control - from package: nsd

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

On Debian possible default full paths are:

/usr/sbin/nsd-control - from package: nsd

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

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