I'm running Ubuntu 13.10. I wanted to change the GRUB timeout by editing the /etc/default/grub file. But there was no such file in my system.
On startup the GRUB menu is displayed and I'm not experiencing any boot problems. If this file was so important for booting, why am I nit experiencing any boot problems?
Reinstall the package and hope for the best:
sudo apt-get --reinstall install grub-pc
Actually the file is not critical for the boot, just to configure the boot when you execute sudo update-grub. If the file doesn't exist, then all values are default ones, like you didn't set them up.
just copy example from /usr/share/grub/default/grub:
sudo cp /usr/share/grub/default/grub /etc/default/
If you really only want to know "why this works", the answer is that LiveCD Ubuntu that you used for installation had this unimportant for boot file \etc\default\grub.cfg, so created yours important for boot /boot/grub/grub.cfg using it.
