switch-pxe-bg-mode: command not found

Have You tried accessing the binary with the full path?

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH

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/switch-pxe-bg-mode - from package: drbl

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