oprof_start: 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/oprof_start - from package: oprofile-gui
/usr/bin/oprof_start - from package: oprofile

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

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