the boot parameter can't be recognized by ubiquity

[vmware-gos-Yuhua]

I spent a lot of time on automatic install for ubuntu desktop 18.04 iso but failed.

The boot option in isolinux/txt.cfg is:

default live-install
label live-install
  menu label ^Install Ubuntu
  kernel casper/vmlinuz
  append file=/cdrom/myubuntu.seed priority=critical languagechooser/language-name=English countrychooser/shortlist=US localechooser/supported-locales=en_US.UTF-8 boot=casper automatic-ubiquity initrd=/casper/initrd quiet splash noprompt ---

It alway stay in the first page with options "Try Ubuntu." and "Install Ubuntu".

I am not sure why the ubiquity can't recognize the boot parameter. Even if something wrong with the file myubuntu.seed. At lease it shouldn't stay in the first install page.

Would you please provide me the detail configuration on how to start the unattended install for ubuntu desktop ?

Thanks very much!