acpihelp: 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/acpihelp - from package: acpica-tools

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

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