why-cpulimit: 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/bin/why-cpulimit - from package: why

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

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