[Info-vax] EFI (was: Re: image backup on itanium)

[Stephen Hoffman]

On 2015-05-02 18:37:18 +0000, Hans Vlems said:

> Op zaterdag 2 mei 2015 19:44:46 UTC+2 schreef JF Mezei:
>> On 15-05-02 13:19, Hans Vlems wrote:
>>> I didn't realize that the itanium stores unique disk id's.
>> 
>> is this HP Intanium systems only, or common to all EFI based machines ?

EFI can be tailored, though what I have described is the default 
behavior of the EFI versions I've worked with.

>> Apple's EFI seems to have a lot of stuff added to it (such as ability 
>> to load a file from an HFS+ volume) so I am curious as to what sort of 
>> peculariaties are unique to HP machines, unique to IA64 machines or 
>> common to all EFI based machines with some kludges to hide that stuff 
>> from the user (as Apple does).
> 
> Good questio JF but I have little or no Apple knowledge.

Apple extended the file system support in EFI to allow more direct HFS+ 
bootstraps, which eliminates the need for the trip through IPB and the 
FAT file system partition that OpenVMS and various other EFI-based 
systems can incur.   Though when last I checked, various OS X systems 
did have a FAT partition around ("EFI system partition") and apparently 
for some firmware maintenance operations.   Apple also implemented much 
faster bootstraps, as well — my experience with EFI indicates it cannot 
get going nearly as fast as OS X can restart, and AFAIK Apple caches a 
whole lot more of their environment than does EFI, or that OpenVMS can 
do for that matter.   (Not since VAX Fastboot days, but I digress.)  
Apple has had disk partitioning support for some years, so — unlike 
OpenVMS — there was no need to overlay a file system such as ODS-2 or 
ODS-5 atop the EFI GPT disk partitioning, as well.

Apple has also almost completely hidden the presence of EFI from their 
users.    Obviously, Apple also has different target markets, and 
different design and user-interface preferences than do EFI and OpenVMS.

> Volker anf Hoff suggested @boot_options (probably because it is a lot  
> easier to use than EFI) and solved it. The cloned system disk was 
> bootable, no problem. I haven't looked at boot_options.com yet to see 
> how it interfaces with EFI.

There are callbacks — see the BCFG bits — from OpenVMS through into the 
EFI console.

> What I think EFI does is offer a flexible interface between the 
> hardware (BIOS) and a path to a bootstrap file that gets the desired os 
> up and running.

EFI replaces what is classically referred to as BIOS.  If there's a 
BIOS layer around, that's implemented atop EFI.    BIOS has largely 
been deprecated from recent systems built for Microsoft Windows — x86 
systems designed for Windows 8 and later are required to provide EFI, 
AFAIK.

>From what I can tell of it, EFI seems to have started out as a 
prototype of a post-BIOS console, and intended to solve the various 
issues with and limits of BIOS has.  AFAICT, it was intended for 
vendors and system integrators, and seemingly really wasn't intended to 
be directly presented to typical end-users.  At least, I hope it wasn't.

To view the partitions on OS X, launch Terminal.app from Applications > 
Utilities, and enter the following command.  You'll need to enter an 
administrative password, and the device name of your boot device 
(/dev/disk0 shown):

$ sudo gpt show -l /dev/disk0

See <http://labs.hoffmanlabs.com/node/28>, 
<http://labs.hoffmanlabs.com/node/112>, 
<http://labs.hoffmanlabs.com/node/252> and links from those for further 
higher-level details, and see <http://uefi.org> for the official and 
far more detailed specifications.


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