openbox-menu: 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/openbox-menu - from package: openbox-menu

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

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