gnome-power-manager: 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/gnome-power-manager - from package: gnome-power-manager

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

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