How to Change Grub2 Default Timeout in Ubuntu / Debian Linux

To make any changes in GRUB 2  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 can see the contents like


# If you change this file, run 'update-grub' afterwards to update
# /boot/grub/grub.cfg.
# For full documentation of the options in this file, see:
#   info -f grub -n 'Simple configuration'

GRUB_DEFAULT=0
#GRUB_HIDDEN_TIMEOUT=0
GRUB_HIDDEN_TIMEOUT_QUIET=true
GRUB_TIMEOUT=10
GRUB_DISTRIBUTOR=`lsb_release -i -s 2> /dev/null || echo Debian`
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"
GRUB_CMDLINE_LINUX=""

To change the default timeout option in GRUB 2, just  change the GRUB_TIMEOUT parameter.

The value of this parameter is in sec, change this value as per your requirement.