nsd: 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 - from package: nsd

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

On Debian possible default full paths are:

/usr/sbin/nsd - from package: nsd
/usr/lib/aolserver4/bin/nsd - from package: aolserver4-daemon

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

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