cpufreq-aperf: 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/bin/cpufreq-aperf - from package: cpufrequtils

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

On Debian possible default full paths are:

/usr/bin/cpufreq-aperf - from package: cpufrequtils

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

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