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Re: Grub module to return partuuid of a device such as (hd0, gpt1) at bo
From: |
Thomas Schmitt |
Subject: |
Re: Grub module to return partuuid of a device such as (hd0, gpt1) at boot time |
Date: |
Sun, 14 Aug 2016 20:24:08 +0200 |
Hi,
i riddled over UEFI appendix A:
> > Do you mean that one has to interpret the statement of UEFI 2.4
> > "All EFI GUIDs (Globally Unique Identifiers) have the format described
> > in RFC 4122 [...]
> > It should also be noted that TimeLow, TimeMid, TimeHighAndVersion fields
> > in the EFI are encoded as little endian."
> > as
> > The text format of EFI GUIDs is the same as in RFC 4122, but the binary
> > representation is byte-swapped at the first 4, 2, and 2 bytes.
Andrei Borzenkov wrote:
> Yes. See other mail I just sent :)
I have to give in, since i am not in the position to raise protest against
Intel et.al. because of obfuscating english language. :))
> > Value "modification-date" produces a low
> > quality GUID from the value set by option --modification-date=.
> How? Time base UUID (Version 1) requires "node data"
I am aware that the result is a poor fake of an UUID. Its time granularity
is below any standard. No site id. So i let it pose as random.
The reason for offering it is to reduce the number of parameters which
one has to remember for reproducibly producing an ISO.
(--modification-date= must be used in any case to override the automatic
"now" timestamping of the ISO filesystem.)
> > The partition GUIDs will be generated in a reproducible way by exoring a
> > little-endian 32 bit counter with the disk GUID beginning at byte offset 9.
> Not sure I follow - what counter?
Partition number. I shall clarify this in the API.
In result the GUID byte strings of a grub-mkrescue GPT will look like
GPT disk GUID : 2303cd2a73c7424aa29825632da7f446
GPT partition GUID : 1 2303cd2a73c7424aa29925632da7f446
GPT partition GUID : 2 2303cd2a73c7424aa29a25632da7f446
GPT partition GUID : 3 2303cd2a73c7424aa29b25632da7f446
GPT partition GUID : 4 2303cd2a73c7424aa29c25632da7f446
In current xorriso, the first partition GUID is the original random
and disk GUID is derived from it as last one:
GPT disk GUID : 6d359a15f8763e47b9ee78207025c200
GPT partition GUID : 1 6d359a15f8763e47b9ea78207025c200
...
GPT partition GUID : 4 6d359a15f8763e47b9e978207025c200
> My copy of 2.4 RevC still does not mention IEEE 802
I have a PDF with title
Unified Extensible Firmware Interface Specification
Version 2.4 Errata B
April, 2014
In appendix A, table 218, row "Node" i read:
"Byte Offset: 10"
"Byte Length: 6"
"Description:
The spatially unique node identifier. This can be based
on any IEEE 802 address obtained from a network
card. If no network card exists in the system, a
cryptographic-quality random number can be used."
> Yes it could be more clear.
They should pay you a reward for compensating this flaw.
Have a nice day :)
Thomas
- Grub module to return partuuid of a device such as (hd0, gpt1) at boot time, Steve Kenton, 2016/08/12
- Re: Grub module to return partuuid of a device such as (hd0, gpt1) at boot time, adrian15, 2016/08/13
- Re: Grub module to return partuuid of a device such as (hd0, gpt1) at boot time, Andrei Borzenkov, 2016/08/13
- Re: Grub module to return partuuid of a device such as (hd0, gpt1) at boot time, Steve Kenton, 2016/08/13
- Re: Grub module to return partuuid of a device such as (hd0, gpt1) at boot time, Andrei Borzenkov, 2016/08/14
- Re: Grub module to return partuuid of a device such as (hd0, gpt1) at boot time, Thomas Schmitt, 2016/08/14
- Re: Grub module to return partuuid of a device such as (hd0, gpt1) at boot time, Andrei Borzenkov, 2016/08/14
- Re: Grub module to return partuuid of a device such as (hd0, gpt1) at boot time, Thomas Schmitt, 2016/08/14
- Re: Grub module to return partuuid of a device such as (hd0, gpt1) at boot time, Thomas Schmitt, 2016/08/14
- Re: Grub module to return partuuid of a device such as (hd0, gpt1) at boot time, Andrei Borzenkov, 2016/08/14
- Re: Grub module to return partuuid of a device such as (hd0, gpt1) at boot time,
Thomas Schmitt <=
- Re: Grub module to return partuuid of a device such as (hd0, gpt1) at boot time, Andrei Borzenkov, 2016/08/14
- Re: Grub module to return partuuid of a device such as (hd0, gpt1) at boot time, Steve Kenton, 2016/08/14
- Adding partition guid/uuid to the probe command for use with Linux kernel command line root=PARTUUID=$guid, Steve Kenton, 2016/08/14
- Re: Adding partition guid/uuid to the probe command for use with Linux kernel command line root=PARTUUID=$guid, Andrei Borzenkov, 2016/08/15
- Re: Adding partition guid/uuid to the probe command for use with Linux kernel command line root=PARTUUID=$guid, Steve Kenton, 2016/08/15
- Re: Grub module to return partuuid of a device such as (hd0, gpt1) at boot time, Michael Zimmermann, 2016/08/14
- Re: Grub module to return partuuid of a device such as (hd0, gpt1) at boot time, Andrei Borzenkov, 2016/08/14
Re: Grub module to return partuuid of a device such as (hd0, gpt1) at boot time, Steve Kenton, 2016/08/13