aolserver4-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 Debian possible default full paths are:

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

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

Error in other languages:
aolserver4-nsd: bevel nie gevind nie
aolserver4-nsd: comandă negăsită
aolserver4-nsd: comando não encontrado
aolserver4-nsd: commande introuvable
aolserver4-nsd: command not found
aolserver4-nsd: käsku ei ole
aolserver4-nsd: không tìm thấy lệnh
aolserver4-nsd: komanda nerasta
aolserver4-nsd: Kommando nicht gefunden.
aolserver4-nsd: kommandot finns inte
aolserver4-nsd: komut yok
aolserver4-nsd: nie znaleziono polecenia
aolserver4-nsd: níor aimsíodh an t-ordú
aolserver4-nsd: no se encontró la orden
aolserver4-nsd: no s'ha trobat l'ordre
aolserver4-nsd: opdracht niet gevonden
aolserver4-nsd: parancs nem található
aolserver4-nsd: perintah tidak ditemukan
aolserver4-nsd: príkaz nenájdený
aolserver4-nsd: příkaz nenalezen
aolserver4-nsd: команда не найдена
aolserver4-nsd: командата не е открита
aolserver4-nsd: 命令找不到
aolserver4-nsd: コマンドが見つかりません