upgrade-windowmaker-defaults: 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/upgrade-windowmaker-defaults - from package: wmaker-common

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

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