I am trying to boot Ubuntu 16.04 LTS as live system from the official ISO image without GUI. In previous versions, the text or textonly boot parameter could be added to the boot options. However, this possibility seems not working for the 16.04 release anymore.
Is there another option of booting without a GUI?
The problem why simply adding the text kernel parameter in GRUB to the live Ubuntu's boot options no longer works since 15.04 is actually our good old friend and enemy systemd once again. It ignores this option and just normally boots to its default target, which is graphical.target for a desktop GUI. For text mode, you would need multi-user.target though.
After a bit of research, I found out that it is indeed possible to specify the systemd target to load as kernel parameter at boot time in GRUB, it is:
systemd.unit=multi-user.target
Append that to the kernel boot options instead of text as you used to do in older releases and you should be fine.
Sources: Arch Wiki: systemd and "Non-graphical boot with systemd" on Unix&Linux
