gen-nonzero-unit: 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/gen-nonzero-unit - from package: piglit

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

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