vp-combined-image-units: 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/vp-combined-image-units - from package: piglit

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

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