drbl-syslinux-netinstall: 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/sbin/drbl-syslinux-netinstall - from package: drbl

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