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I have a dual Windows 7/Ubuntu system which I almost always boot into Windows. When I boot into Ubuntu it makes memtest the default boot menu option. Whilst this is annoying I could live with it if I were able to change the default back from the grub command line available from the boot menu. I don't want to have to boot into Ubuntu to fix this problem every time.

I am able to find the grub config file and can see the contents (sort of) by using:

cat (hd0,5)/boot/grub/grub.cfg

(although this only shows me the 'tail' not the whole file).

and the command:

configfile (hd0,5)/boot/grub/grub.cfg

executes this configuration (again).

Is it possible to edit this file from the grub command line?

The grub (1.99) manual suggests that I can use the Environment Block to:

set the default menu entry based on what was selected the last time

which may fix my problem but I can't find any examples of their use... Can I somehow use the save_env and load_env commands?

Note: I have grub version 1.98

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3 Answers

up vote 8 down vote accepted
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No, there is no way to change the default boot menu from the grub command line. The easiest way to do this is by booting into Linux.

Next time you boot, look at the order of boot options. Let's say you want to make Windows the default boot option, note down the line it is on, i.e. the 4th or whatever.

Edit /etc/default/grub

Find the line -

GRUB_DEFAULT=0

Subtract 1 from the number you noted above, let's it was 4 and change the text to read

GRUB_DEFAULT=3


Run update-grub2 from the shell.

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Can I do this from the grub command line (accessed from the boot screen)? How do I edit the file from there? –  Matthew Murdoch Sep 27 '11 at 12:52
    
You can't make the changes I described without booting into linux. If you can't boot the installed system, you can use a live cd. –  bryan Sep 28 '11 at 5:16
1  
So the answer to my original question is 'No (it is not possible)'? –  Matthew Murdoch Sep 28 '11 at 8:18
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Using the Super Grub Disk is easier than using a live CD.

See this tutorial : GRUB 2 recovery.

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To change the default boot of Backtrack 5 R3 to Windows 7 or any other OS then you must first make a note of what line in the list the option is on as you will need it in step 2. My Windows 7 boot option is on Line 5. Let's open the file we need to edit;

root@bt:~# gedit /boot/grub/grub.cfg

Then find the following line (it's on line 12 in mine)

set default="0"

Now subtract 1 from your chosen boot menu line i asked you to remember earlier, mine was on line 5 so i change the "0" to a "4"

set default="4"

Now click on save, then close down everything you have open and restart your computer to check it has worked, you should now find your chosen boot option highlighted.

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