copy-pixels: 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/copy-pixels - from package: piglit

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

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