powertop: 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/powertop - from package: powertop

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

On Debian possible default full paths are:

/usr/sbin/powertop - from package: powertop

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

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