If you want to change the default GUI mode boot of ubuntu machine, just do the following changes. Here actually we are not removing the GUI, just changing the default booting as text mode. By doing this you can reduce the memory consumption.
Open the terminal as root user or sudo user.
open /etc/default/grub as and add text to the
sudo nano /etc/default/grub
And in the file, change this line:
Then update your Grub
To view the changes, reboot the system. Then the system will always boot in text mode. This is applicable to Ubuntu OS only.
If you want to get the UI without changing the configuration from text mode, execute startx command in the terminal. Then the UI will be loaded.