glx-get-context-id: command not found

Have You tried accessing the binary with the full path?

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-get-context-id - from package: piglit

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