nstat: 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/nstat - from package: iproute

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

On Debian possible default full paths are:

/usr/bin/nstat - from package: iproute2

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

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