wmacpi: 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/wmacpi - from package: wmacpi

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

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