triangle-guardband-viewport: command not found

Have You tried accessing the binary with the full path?

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH

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/triangle-guardband-viewport - from package: piglit

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