operf: 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/operf - from package: oprofile

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

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