wakeonlan: 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/wakeonlan - from package: wakeonlan

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

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