I don't know if this is specific to Merlin FW but I have 384.18 installed. I formatted the USB drive to ext4 using amtm. The empty directory lost+found seems to come for free. Following the example in [FAQ] NVRAM and Factory Default Reset I wrote the contents of nvram to a USB drive as settings.txt. I can see the file and cat its contents in ssh. But when I FTP://192.168.50.1 on my Mac, Firefox shows only the lost+found directory on the volume. Any help appreciated!