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Re: dual grub install?

From: Chris Murphy
Subject: Re: dual grub install?
Date: Thu, 7 Jun 2012 11:57:27 -0600

On Jun 7, 2012, at 6:50 AM, Tom Davies wrote:

> There were 2 points about Cds/Dvds as recovery media.  
> 1.  An old fella keeps a £2 coin in his bus-pass wallet in case he loses his 
> bus-pass and needs to pay for the ticket.  
> 2.  If you need to reinstall Windows then you need the Recovery Media to work 
> otherwise you will have to buy a fresh Install Media which costs around 
> £100-£200.

Newer versions of Apple firmware supports network booting from the internet. So 
even if the drive is FUBAR, replaced with a blank disk, and you don't have any 
install media, you can still boot and install a replacement OS. This is better 
than craptastic CD/DVD media. It's better than USB sticks too which get lost, 
but obviously it is a slow recovery method.

One of the few advantages of EFI over BIOS.

> In addition most non-Windows systems allow you to set-up LiveCd/Dvd, LiveUsb 
> or whatever you want.

Last summer's Mac OS 10.7 release is the first that has a kinda sorta live boot 
environment. It's limited to a handful of applications: Disk Utility, Safari, 
OS installer, password reset, firmware lock tool, and terminal. There is no 
navigable desktop environment so no means of launching other apps. So I'd say 
most Linux distros offer a liveCD/DVD. I don't even know how common this is for 
FreeBSD or OpenSolaris/Indiana.

But a big point of Live media is the "try me" mentality. That's missing by both 
MS and Apple, who mutually (but independently) question the notion of running 
any other operating system.

> Each and every partition on the boot-drive can have a boot-loader BUT the MBR 
> can only point to one of them.

Putting all or part of core.img into partition boot sectors is not recommended 
with GRUB2. Recommended is either MBR gap where partition 1 starts at sector 
2048, leaving enough room in the gap for core.img between the MBR and partition 
1. Or for GPT disks, using BIOS Boot partition type, size 1MB.

And with UEFI hardware, all of this is completely different.

> Apparently quite a few people that have to maintain pcs install grub purely 
> to avoid having to rely on the flaky Windows one even on machines that really 
> do only have Windows.  

UEFI hardware that comes with Windows 8 pre-installed will have Secure Boot 
enabled. You'll have to disable Secure Boot in order to use GRUB2 EFI as a boot 
loader the way you use it today. If you want to take advantage of Secure Boot 
to avoid boot loader attacks now in the wild, you'll need a way to have the 
boot loader, kernel, and modules signed. This is non-trivial, especially for 
those who role their own kernels. Dynamic GRUB2 module loading also would have 
to be disabled in a Secure Boot context, or it's possible the module being 
loaded is actually malware and then the whole point of Secure Boot is 

> The way i would deal with it is to edit the config files
> so that Grub defaults into the right version of Windows.  I think the 
> "Default =" starts counting 0, 1, 2 so probably you will want it to boot line 
> 1 of the grub menu, or maybe line 2 i'm not sure.  

You are better off adding:
GRUB_DEFAULT="Title of the system you want to boot"

to /etc/default/grub

And running grub-mkconfig. You can't always be assured that the entry you want 
as default will be in a particular ordered slot. But you can be assured of its 

Chris Murphy

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