xscreensaver-gl-helper: 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/bin/xscreensaver-gl-helper - from package: xscreensaver-gl-base

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

On Debian possible default full paths are:

/usr/bin/xscreensaver-gl-helper - from package: xscreensaver-gl

You may install the required package with command apt-get install {package}

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