glx-swap-singlebuffer: 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/glx-swap-singlebuffer - from package: piglit

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

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