glsl-deriv-varyings: 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-deriv-varyings - from package: piglit

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

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