copy_buffer_coherency: 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_buffer_coherency - from package: piglit

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

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