iwpriv: 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:

/sbin/iwpriv - from package: wireless-tools

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

On Debian possible default full paths are:

/sbin/iwpriv - from package: wireless-tools

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

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