GRUB 2 is the next generation of GNU GRUB, using version numbers 1.90 and above. GRUB 2 is a complete rewrite. The most important goal is to make GNU GRUB cleaner, safer, more robust, more portable and more powerful.
If you're already familiar with GRUB Legacy, you'll find that the GRUB 2 configuration file is similar in broad strokes, but it varies in many details. You should be aware of alternative means of configuring GRUB 2, as well.
To make any changes the way GRUB 2 works you need to edit the main GRUB 2 configuration file located in /etc/default/ folder, you can edit it by running the following command from terminal:
sudo gedit /etc/default/grub you should see the content very similar to this ....
# If you change this file, run 'update-grub' afterwards to update
# /boot/grub/grub.cfg.
GRUB_DEFAULT=0
#GRUB_HIDDEN_TIMEOUT=0
GRUB_HIDDEN_TIMEOUT_QUIET=true
GRUB_TIMEOUT=7
GRUB_DISTRIBUTOR=`lsb_release -i -s 2> /dev/null || echo Debian`
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"
GRUB_CMDLINE_LINUX=""
# Uncomment to enable BadRAM filtering, modify to suit your needs
# This works with Linux (no patch required) and with any kernel that obtains
# the memory map information from GRUB (GNU Mach, kernel of FreeBSD ...)
#GRUB_BADRAM="0x01234567,0xfefefefe,0x89abcdef,0xefefefef"
# Uncomment to disable graphical terminal (grub-pc only)
#GRUB_TERMINAL=console
# The resolution used on graphical terminal
# note that you can use only modes which your graphic card supports via VBE
# you can see them in real GRUB with the command `vbeinfo'
GRUB_GFXMODE=640x480
# Uncomment if you don't want GRUB to pass "root=UUID=xxx" parameter to Linux
#GRUB_DISABLE_LINUX_UUID=true
# Uncomment to disable generation of recovery mode menu entries
#GRUB_DISABLE_LINUX_RECOVERY="true"
# Uncomment to get a beep at grub start
#GRUB_INIT_TUNE="480 440 1"
Change default Timeout:
To change the default timeout option in GRUB 2, you just need to change the GRUB_TIMEOUT parameter. The value of this parameter is in sec, change this value as per your requirement.
Change the default boot option:
To change the default boot option in GRUB 2, you just need to change the GRUB_DEFAULT parameter. 0 is the first entry, so if you want Windows to be your default boot option which is, say at, 5th position in the grub menu, then you just need to change the GRUB_DEFAULT value to 4 and save the file and close it. Save the file after making all the required changes and from the terminal run the following command
sudo update-grub
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