arb_sample_shading-builtin-gl-num-samples: 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/arb_sample_shading-builtin-gl-num-samples - from package: piglit

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

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