How to remove prompt for ejecting cd on ubuntu 16.04 iso

Question

I'm trying to create an iso that runs a script and turns off the machine (based off of the instructions listed by Peter Pudlak here).

With a few tweaks, everything seems to work on a ubuntu 16.04 iso. However, when I power off the machine, I'm prompted to eject the cd on shutdown. The machine does not power off until I manually hit enter. I'm trying to automate this process and can't manually hit enter when prompted. Is there a way to either

1. Force turning off the machine without hitting this prompt or
2. Customizing the iso further so that it doesn't have this behavior?

This article explains how to do what I want, but the files that it lists in step 6 are not part of a ubuntu 16.04 desktop iso. Any pointers would be appreciated.

Answer 1

After obtaining the base system for the Ubuntu ISO, edit the file /etc/rc0.d/S89casper and make the following modifications:

# eject -p -m /cdrom >/dev/null 2>&1

# [ "$prompt" ] || return 0
## Add the following line: 
return 0

# XXX - i18n
# MSG="Please remove the disc and close the tray (if any) then press ENTER: "

# Modify 
/sbin/usplash_write "TIMEOUT 86400"

# To read 
/sbin/usplash_write "TIMEOUT 0"

See: https://askubuntu.com/a/87508/214875

Answer 2

In the Ubuntu 16.04 Live CD, the script that ejects the CD and waits for the keypress seems to be /sbin/casper-stop.

It's probably better not to delete the script, but if you comment out the lines plymouth watch-keystroke > /dev/null and read x < /dev/console, they should prevent the system from waiting for the Enter key.