Save ISO image to a linux box, which you have sudo or root access
Because you need to mount ISO image to extract the content and modified it..
Mount ISO image and make a copy to modify
Next is to mount ISO image using loop mount so that we can access the files inside ISO image.
Since ISO image mount is typically read only, we need to make a copy from ISO mounting directory.
Please use either root or sudo to do the following commands.
Modify SYSLINUX boot config and Linux boot kernel config
Ubuntu ISO image uses [syslinux] (http://www.syslinux.org/) as bootloader. By default, it uses VGA as graphic output.
We need disable graphic and make it goes to serial port/console ttyS0 by modifying files:
Remake ISO image using mkisofs
Boot ISO image in headless box to install
Burn ISO image into CD, and boot ISO image in a headless box through CDROM, connect serial/console port with speed 115200, wow!
Following the usual installation steps to complete installation.
After installation is complete, boots!
Ubuntu server can be installed in a headless box, which has even less 2GB disk space.