guess: 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 - from package: nvram-wakeup

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

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