xacpi-simple: 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 Debian possible default full paths are:

/usr/bin/xacpi-simple - from package: chiark-utils-bin

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

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