drawbuffer-modes: 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/lib64/piglit/bin/drawbuffer-modes - from package: piglit

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

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