Question: This morning linux-image-3.5.0-26-generic was installed during a software update. On my laptop this proved to be unusable after 10 minutes. I changed to linux-image-3.5.0-24-generic and all seems fine. I have updated the default grub2 selection to the 24-generic. How can I lock the default grub selection to this value so subsequent updates don't overwrite and make themselves default?

Answer: 
you can use this tool, Grub Customizer. To download,
Open terminal and type:

> 
> sudo add-apt-repository ppa:danielrichter2007/grub-customizer [enter]
> 
> 
> sudo apt-get update [enter]
> 
> 
> sudo apt-get install grub-customizer [enter]
> 
> 
> 

Open dash and search grub customizer, and run it. Edit configuration with this tool.it's easy . Go to General Settings to edit the default, time boot etc

![enter image description here](https://i.stack.imgur.com/pH0ux.png)
I just searched and found this file:

```
/etc/default/grub

```

Command `grub-mkconfig` (or `update-grub`) uses this file for default values. Try editing line `GRUB_DEFAULT=0` to `GRUB_DEFAULT=1`.