On 2023-04-03 12:52, bad sector wrote:
> On 3/22/23 07:42, Carlos E.R. wrote:
>> On 2023-03-22 12:01, bad sector wrote:
>>> On 3/21/23 23:55, Malcolm wrote:
>>>> On Tue, 21 Mar 2023 21:23:40 -0400
>>>> bad sector <forgetski@INVALID.net> wrote:
>>>> <snip>
>>>>
>>>>> But none of this is getting me any closer to getting a handle on the
>>>>> difference between 1 & 3 in the OP, or on the need to use the system
>>>>> partition as a "Boot Partition" when there already is a definitive
>>>>> "BIOS Boot" partition. I figure a little more verbose help bubbles on
>>>>> that dialog would be useful.
>>>> Hi
>>>> BIOS Boot (type pmbr_boot) is need when using Legacy Boot and a gpt
>>>> disk.
>>>
>>> I do have a GPT disk and having no need for EFI I do use legacy boot
>>
>> Yes, you do need it.
>
> The BIOS-Boot yes, not that other horror

Man, it doesn't harm to have an empty 500 MB partition there.

>
>> You actually need the "Bios Boot" partition, usually of 8 MiB size,
>> because you are using legacy boot.
>
> While in the disk root world, would Truncated-MBR not be a much better
> name for Protected-MBR? In fact Truncated-Root-Sector would be even
> better seeing that MBR doesn't say much but Root-Sector does.

It is not truncated. You are free to use it fully, but you can cause
disasters.

It is not protected-mbr, but protective-mbr.

>
>>
>> And YaST will also insist, with good reasons, despite your
>> protestations, that you need an ESP partition, which you call EFI
>> partition (it is "EFI system partition, that is, ESP). Just let YaST
>> create it. It is quite small, and if you actually need it next decade
>> and don't have it, you will grind your teeth.
>
> Next decade I might well be grinding and not just my teeth anyway :-)
>
> I use fdisk of gfdisk or whatever to partition my disks because I want
> partitions to be exactly sized with identical block numbers so that (if
> needed) one system can be just dd'd to another partition. Gui
> partitioners have a very long way to go to get me aboard especially if
> their *microcancer-coefficient* leans heavily toward the 'virtualise
> everything and keep the user in the mushromm factory by keeping him in
> the dark and feeding him manure'.

That doesn't contradict what I said in the least.

--
Cheers, Carlos.

On 4/3/23 14:24, Carlos E.R. wrote:
> On 2023-04-03 12:52, bad sector wrote:
>> On 3/22/23 07:42, Carlos E.R. wrote:
>>> On 2023-03-22 12:01, bad sector wrote:
>>>> On 3/21/23 23:55, Malcolm wrote:
>>>>> On Tue, 21 Mar 2023 21:23:40 -0400
>>>>> bad sector <forgetski@INVALID.net> wrote:
>>>>> <snip>
>>>>>
>>>>>> But none of this is getting me any closer to getting a handle on the
>>>>>> difference between 1 & 3 in the OP, or on the need to use the system
>>>>>> partition as a "Boot Partition" when there already is a definitive
>>>>>> "BIOS Boot" partition. I figure a little more verbose help bubbles on
>>>>>> that dialog would be useful.
>>>>> Hi
>>>>> BIOS Boot (type pmbr_boot) is need when using Legacy Boot and a gpt
>>>>> disk.
>>>>
>>>> I do have a GPT disk and having no need for EFI I do use legacy boot
>>>
>>> Yes, you do need it.
>>
>> The BIOS-Boot yes, not that other horror
>
> Man, it doesn't harm to have an empty 500 MB partition there.

Probably entirely futile given the current state of the art but I was
tought early on not to leave any place on a disk that doesn't carry the
risk of of a defrag storm or similar hiding-place destruction by
overwrite. Since the diskware never allocates bad sectors anyway, this
used to mean not leaving any space that is not formatted and somehow
(=unpredictably) in use.

>>> You actually need the "Bios Boot" partition, usually of 8 MiB size,
>>> because you are using legacy boot.
>>
>> While in the disk root world, would Truncated-MBR not be a much better
>> name for Protected-MBR? In fact Truncated-Root-Sector would be even
>> better seeing that MBR doesn't say much but Root-Sector does.
>
> It is not truncated. You are free to use it fully, but you can cause
> disasters.
>
> It is not protected-mbr, but protective-mbr.

I don't really know what MBR is (seeing that that acronym doesn't even
hint at any physical description) but unlesss I missed something the
once exclusive root sector (a very definitive physical descriptor) is no
longer entirely reserved for booting so only a part of it may used for
that. To me that means truncated in use at least if not physically.

>>> And YaST will also insist, with good reasons, despite your
>>> protestations, that you need an ESP partition, which you call EFI
>>> partition (it is "EFI system partition, that is, ESP). Just let YaST
>>> create it. It is quite small, and if you actually need it next decade
>>> and don't have it, you will grind your teeth.
>>
>> Next decade I might well be grinding and not just my teeth anyway :-)
>>
>> I use fdisk of gfdisk or whatever to partition my disks because I want
>> partitions to be exactly sized with identical block numbers so that
>> (if needed) one system can be just dd'd to another partition. Gui
>> partitioners have a very long way to go to get me aboard especially if
>> their *microcancer-coefficient* leans heavily toward the 'virtualise
>> everything and keep the user in the mushromm factory by keeping him in
>> the dark and feeding him manure'.
>
> That doesn't contradict what I said in the least.

I would never want to contradict you because for one thing I have no use
for it but the last time I 'looked at' one of them GUI partitioners
(probably 20+ years ago) it did not cater to defining starting and
ending blocks. Maybe I should 'take another look' but I don't have any
use for that either :-)

On 2023-04-03 21:34, bad sector wrote:
> On 4/3/23 14:24, Carlos E.R. wrote:
>> On 2023-04-03 12:52, bad sector wrote:
>>> On 3/22/23 07:42, Carlos E.R. wrote:
>>>> On 2023-03-22 12:01, bad sector wrote:
>>>>> On 3/21/23 23:55, Malcolm wrote:
>>>>>> On Tue, 21 Mar 2023 21:23:40 -0400
>>>>>> bad sector <forgetski@INVALID.net> wrote:
>>>>>> <snip>
>>>>>>
>>>>>>> But none of this is getting me any closer to getting a handle on the
>>>>>>> difference between 1 & 3 in the OP, or on the need to use the system
>>>>>>> partition as a "Boot Partition" when there already is a definitive
>>>>>>> "BIOS Boot" partition. I figure a little more verbose help
>>>>>>> bubbles on
>>>>>>> that dialog would be useful.
>>>>>> Hi
>>>>>> BIOS Boot (type pmbr_boot) is need when using Legacy Boot and a gpt
>>>>>> disk.
>>>>>
>>>>> I do have a GPT disk and having no need for EFI I do use legacy boot
>>>>
>>>> Yes, you do need it.
>>>
>>> The BIOS-Boot yes, not that other horror
>>
>> Man, it doesn't harm to have an empty 500 MB partition there.
>
> Probably entirely futile given the current state of the art but I was
> tought early on not to leave any place on a disk that doesn't carry the
> risk of of a defrag storm or similar hiding-place destruction by
> overwrite. Since the diskware never allocates bad sectors anyway, this
> used to mean not leaving any space that is not formatted and somehow
> (=unpredictably) in use.
>
>
>>>> You actually need the "Bios Boot" partition, usually of 8 MiB size,
>>>> because you are using legacy boot.
>>>
>>> While in the disk root world, would Truncated-MBR not be a much
>>> better name for Protected-MBR? In fact Truncated-Root-Sector would be
>>> even better seeing that MBR doesn't say much but Root-Sector does.
>>
>> It is not truncated. You are free to use it fully, but you can cause
>> disasters.
>>
>> It is not protected-mbr, but protective-mbr.
>
> I don't really know what MBR is (seeing that that acronym doesn't even
> hint at any physical description) but unlesss I missed something the
> once exclusive root sector (a very definitive physical descriptor) is no
> longer entirely reserved for booting so only a part of it may used for
> that. To me that means truncated in use at least if not physically.

Well, wrong interpretation.

The MBR on a GPT partitioned disk is fully there, same as before, and
can not be used for something else.

A machine with traditional BIOS, using Linux, will boot from it, but
ignore its partition definitions it might have (it may warn about it).

A machine using UEFI will ignore it totally (but should complain if its
contents are incorrect).

>
>
>
>>>> And YaST will also insist, with good reasons, despite your
>>>> protestations, that you need an ESP partition, which you call EFI
>>>> partition (it is "EFI system partition, that is, ESP). Just let YaST
>>>> create it. It is quite small, and if you actually need it next
>>>> decade and don't have it, you will grind your teeth.
>>>
>>> Next decade I might well be grinding and not just my teeth anyway :-)
>>>
>>> I use fdisk of gfdisk or whatever to partition my disks because I
>>> want partitions to be exactly sized with identical block numbers so
>>> that (if needed) one system can be just dd'd to another partition.
>>> Gui partitioners have a very long way to go to get me aboard
>>> especially if their *microcancer-coefficient* leans heavily toward
>>> the 'virtualise everything and keep the user in the mushromm factory
>>> by keeping him in the dark and feeding him manure'.
>>
>> That doesn't contradict what I said in the least.
>
> I would never want to contradict you because for one thing I have no use
> for it but the last time I 'looked at' one of them GUI partitioners
> (probably 20+ years ago) it did not cater to defining starting and
> ending blocks. Maybe I should 'take another look' but I don't have any
> use for that either :-)

I'm not saying any of that. Use whatever tool you wish, create the
partitions specifying exact amount of LBAs and you can clone them just fine.

I'm saying that YaST will want an ESP partition and/or a "Bios Boot"
partition. I say "do not interfere". Let those partitions be, do not
complain.

--
Cheers, Carlos.

On Mon, 3 Apr 2023 15:34:20 -0400
bad sector <forgetski@invalid.org> wrote:

<snip>
> >
> > It is not protected-mbr, but protective-mbr.
>
> I don't really know what MBR is (seeing that that acronym doesn't
> even hint at any physical description) but unlesss I missed something
> the once exclusive root sector (a very definitive physical
> descriptor) is no longer entirely reserved for booting so only a part
> of it may used for that. To me that means truncated in use at least
> if not physically.
>
<snip>
Hi
Master Boot Record where the boot code goes on a dos type disk that
could be hacked, hence the move to gpt and protected mbr boot location.

--
Cheers Malcolm °¿° (Linux Counter #276890)
Tumbleweed 20230402 | GNOME Shell 44.0 | 6.2.9-1-default
HP Z440 | Xeon E5-2690 V3 X24 @ 2.60GHz | Nvidia Quadro T400/Tesla P4
up 9:32, 3 users, load average: 0.08, 0.27, 0.28

On 2023-04-03 23:16, Malcolm wrote:
> On Mon, 3 Apr 2023 15:34:20 -0400
> bad sector <forgetski@invalid.org> wrote:
>
> <snip>
>>>
>>> It is not protected-mbr, but protective-mbr.
>>
>> I don't really know what MBR is (seeing that that acronym doesn't
>> even hint at any physical description) but unlesss I missed something
>> the once exclusive root sector (a very definitive physical
>> descriptor) is no longer entirely reserved for booting so only a part
>> of it may used for that. To me that means truncated in use at least
>> if not physically.
>>
> <snip>
> Hi
> Master Boot Record where the boot code goes on a dos type disk that
> could be hacked, hence the move to gpt and protected mbr boot location.
>

??????

You can write anything into the MBR, it is not protected in any manner.

It is called "protective MBR", and it is there simply to protect ancient
software that do not understand GPT disks from causing damage to the
disk by altering its partitions. The ancient software is fooled into
thinking it it is dealing with a normal disk with MBR.

<https://answers.microsoft.com/en-us/windows/forum/all/uefi-based-pc-protective-mbr-what-is-it/0fc7b558-d8d4-4a7d-bae2-395455bb19aa>

<https://en.wikipedia.org/wiki/Master_boot_record>

<https://en.wikipedia.org/wiki/GUID_Partition_Table#Protective_MBR_(LBA_0)>

«Protective MBR (LBA 0)

For limited backward compatibility, the space of the legacy Master Boot
Record (MBR) is still reserved in the GPT specification, but it is now
used in a way that prevents MBR-based disk utilities from misrecognizing
and possibly overwriting GPT disks. This is referred to as a protective
MBR.[11]

A single partition of type EEh, encompassing the entire GPT drive (where
"entire" actually means as much of the drive as can be represented in an
MBR), is indicated and identifies it as GPT. Operating systems and tools
which cannot read GPT disks will generally recognize the disk as
containing one partition of unknown type and no empty space, and will
typically refuse to modify the disk unless the user explicitly requests
and confirms the deletion of this partition. This minimizes accidental
erasures.[11] Furthermore, GPT-aware OSes may check the protective MBR
and if the enclosed partition type is not of type EEh or if there are
multiple partitions defined on the target device, the OS may refuse to
manipulate the partition table.[12]

If the actual size of the disk exceeds the maximum partition size
representable using the legacy 32-bit LBA entries in the MBR partition
table, the recorded size of this partition is clipped at the maximum,
thereby ignoring the rest of the disk. This amounts to a maximum
reported size of 2 TiB, assuming a disk with 512 bytes per sector (see
512e). It would result in 16 TiB with 4 KiB sectors (4Kn), but since
many older operating systems and tools are hard coded for a sector size
of 512 bytes or are limited to 32-bit calculations, exceeding the 2 TiB
limit could cause compatibility problems.[11]»

--
Cheers, Carlos.

On 4/3/23 17:44, Carlos E.R. wrote:
> On 2023-04-03 23:16, Malcolm wrote:
>> On Mon, 3 Apr 2023 15:34:20 -0400
>> bad sector <forgetski@invalid.org> wrote:
>>
>> <snip>
>>>>
>>>> It is not protected-mbr, but protective-mbr.
>>>
>>> I don't really know what MBR is (seeing that that acronym doesn't
>>> even hint at any physical description) but unlesss I missed something
>>> the once exclusive root sector (a very definitive physical
>>> descriptor) is no longer entirely reserved for booting so only a part
>>> of it may used for that. To me that means truncated in use at least
>>> if not physically.
>>>
>> <snip>
>> Hi
>> Master Boot Record where the boot code goes on a dos type disk that
>> could be hacked, hence the move to gpt and protected mbr boot location.
>
> ??????
>
> You can write anything into the MBR, it is not protected in any manner.

You can write anything to any part of any disk. I'm no guru or even a
lowercase geek but it seems to me that MBR is not a place, it's a code;
the 'place' is the 'root sector', there never was a place that was the
MBR although many have used the term in that sense. That's my take on it
anyway, I'm open to enlightment.

From a security point of view the idea is (or WAS back in the day) to
never leave any place of 'guaranteed-survivability' on any medium for
uninvited code and it's in this sense that I'm not sure why I would want
to have an EFI partition that I do not need unless I wiped it every
minute. Today far more sophisticated methods exist but that doesn't make
old-school defenses useless.

On 2023-04-04 15:01, bad sector wrote:
> On 4/3/23 17:44, Carlos E.R. wrote:
>> On 2023-04-03 23:16, Malcolm wrote:
>>> On Mon, 3 Apr 2023 15:34:20 -0400
>>> bad sector <forgetski@invalid.org> wrote:
>>>
>>> <snip>
>>>>>
>>>>> It is not protected-mbr, but protective-mbr.
>>>>
>>>> I don't really know what MBR is (seeing that that acronym doesn't
>>>> even hint at any physical description) but unlesss I missed something
>>>> the once exclusive root sector (a very definitive physical
>>>> descriptor) is no longer entirely reserved for booting so only a part
>>>> of it may used for that. To me that means truncated in use at least
>>>> if not physically.
>>>>
>>> <snip>
>>> Hi
>>> Master Boot Record where the boot code goes on a dos type disk that
>>> could be hacked, hence the move to gpt and protected mbr boot location.
>>
>> ??????
>>
>> You can write anything into the MBR, it is not protected in any manner.
>
> You can write anything to any part of any disk. I'm no guru or even a
> lowercase geek but it seems to me that MBR is not a place, it's a code;

It is a place, its name is MBR. Not "root sector". MBR is not a code.
However, the MBR contains both a partition table and some code. That
doesn't make it "code".

> the 'place' is the 'root sector', there never was a place that was the
> MBR although many have used the term in that sense. That's my take on it
> anyway, I'm open to enlightment.
>
> From a security point of view the idea is (or WAS back in the day) to
> never leave any place of 'guaranteed-survivability' on any medium for
> uninvited code and it's in this sense that I'm not sure why I would want
> to have an EFI partition that I do not need unless I wiped it every
> minute. Today far more sophisticated methods exist but that doesn't make
> old-school defenses useless.
>
>
>
>

--
Cheers, Carlos.