fragment-center: 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/fragment-center - from package: piglit

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

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