guess-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 Debian possible default full paths are:

/usr/sbin/guess-helper - from package: nvram-wakeup

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

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