On Jun 18, 2014, at 10:06 PM, Ganapatrao Kulkarni <gpkulka...@gmail.com> wrote:

> Hi All,
> 
> I am trying to boot GRUB present at HARD-DISK connected over PCI and in AHCI 
> mode.
> I am able to boot by setting default boot path as below.
> 
> gArmPlatformTokenSpaceGuid.PcdDefaultBootDevicePath|L"PciRoot(0x1)/Pci(0x0,0x0)/Sata(0x0,0x0,0x0)/HD(1,GPT,E3AE6975-BACE-464E-91E1-BB4FE9954047,0x800,0x31801)/\EFI\BOOT\BOOTAA64.EFI"
> 
> however, i see the Partition GUID(Partition unique GUID: 
> E3AE6975-BACE-464E-91E1-BB4FE9954047) which is part of path changes when ever 
> hard disk is repartitioned or created with partition.
> 
> are there any other way to set the default boot path which is consistent and 
> not depends on GUID.
> 

No but you can form the device path like: 
HD(1,GPT,E3AE6975-BACE-464E-91E1-BB4FE9954047,0x800,0x31801)/\EFI\BOOT\BOOTAA64.EFI”
 so that if the hard disk is moved around in the system you can still boot from 
it. 

There is no concept of C: or a magic sector in GPT. The 3rd party MBR boot 
managers where causing chaos back in the day as the all tried to grab the same 
hidden sectors on the disk. Also moving a disks location caused the system to 
fail to boot. So GPT was design to solve those problems. There is nothing on 
the disk that that indicates what is bootable, that info is stored in EFI NVRAM 
as it is platform policy. 

So when you install a new OS on your system you need to run some kind of 
install program to set the EFI NVRAM boot variable. 

The BDS processes the EFI boot variables, and it looks like that PCD is used to 
set a default value. What happens if no bootable variables resolve is platform 
policy. So you could implement a custom boot manager that does some magic. For 
example you could define a PartitionTypeGUID that represents an EFI Application 
(OS Loader) that helps the user select which partition on the disk should be 
bootable. Or you could set the platform policy to network boot if the hard 
drive boot fails, and have the system run an EFI Application that helps you 
setup (or provision) the boot options.

Thanks,

Andrew Fish

> thanks
> Ganapat
> 
> 
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HPCC Systems Open Source Big Data Platform from LexisNexis Risk Solutions
Find What Matters Most in Your Big Data with HPCC Systems
Open Source. Fast. Scalable. Simple. Ideal for Dirty Data.
Leverages Graph Analysis for Fast Processing & Easy Data Exploration
http://p.sf.net/sfu/hpccsystems
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