Changing the default boot option with GRUB2

Gone are the days of the nice /boot/grub/menu.lst file, but with new tools comes new features.

Changing the default boot item

In Grub2 you can change the default boot entry by editing the /etc/default/grub file.
In this file you’ll see something like this near the top:

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=""

The first line above tells Grub to boot the first boot entry by default (menu item with index 0).

You can simply change this to menu entry you prefer, but whenever you make any change to this file you need to run the following command to make the changes take effect:

$> sudo update-grub

Changing the default boot entry from the command line

A new feature that Grub2 provides is to change this option dynamically from the command-line.

In order for this to work, instead of setting the GRUB_DEFAULT option to the desired index, set it to saved instead, like this:

GRUB_DEFAULT=saved

And run update-grub to make the changes take effect:

Now you can use the grub-set-default and the grub-reboot commands.

Both commands take the index of the boot entry you want as a command line argument:

$> grub-set-default <entry>

This command will permanently set the default boot entry to the index specified on the command line, useful if you tend to change the default regularly.

$> grub-reboot <entry>

This command will reboot the machine and boot into the specified boot entry, but only that once. The following boot will use the default.