prepare-files-for-PXE-client: 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/share/drbl/sbin/prepare-files-for-PXE-client - from package: drbl

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

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