glx-import-context-single-process: 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-import-context-single-process - from package: piglit

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

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