glsl-reload-source: 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/glsl-reload-source - from package: piglit

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

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