Uefi and porteus 3.0

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brokenman
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Re: Uefi and porteus 3.0

Post#31 by brokenman » 15 Sep 2014, 18:48

I understand you only want to talk about flash devices, but the problem is we simply can't assume that a user will install Porteus only to a flash device. It is a portable distro that we report to be installable on all devices. This includes optical, SSD, SCSI, HDI and flash.
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Re: Uefi and porteus 3.0

Post#32 by Ed_P » 15 Sep 2014, 19:57

brokenman wrote:we simply can't assume that a user will install Porteus only to a flash device.
Can't Porteus determine a device type? If the device is sdbx or higher it implies it's not the machine's hard drive does it not? Or check it's size and if it's 64 MB or less allow the format option to be skipped? (I'm not aware of any machines build in the past 10 yrs with hard drives that small. Years ago yes but not in this century.)

And to be clear I'm talking about your UEFI install script not the standard Porteus install script.
Ed

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Re: Uefi and porteus 3.0

Post#33 by brokenman » 16 Sep 2014, 01:25

Simply put ... a hybrid MBR is not going to happen. For now we will have to stick with just a plain MBR that loads Porteus (on a FAT32 partition :cry: ) that is big enough for windows to use as storage. This means it will be bootable in both EFI and BIOS systems and windows 7/vista should have no problem seeing the device. People with 2T+ devices will need to use a GPT to get full benefits. Thanks fanthom. Case closed.
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Re: Uefi and porteus 3.0

Post#34 by Ed_P » 16 Sep 2014, 13:26

brokenman wrote:Simply put ... a hybrid MBR is not going to happen.
For the record, the approach I use did not create a "hybrid MBR" or a "protected MBR", it uses the MBR that the Porteus Install app creates. It then uses GDISK's option to create the GUID Partition Table (GPT) from the MBR. Nothing in the MBR is changed.
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Re: Uefi and porteus 3.0

Post#35 by brokenman » 17 Sep 2014, 21:39

If you created an MBR together with a GPT then you are looking at a hybrid MBR. That's what hybrid means. Also, I am pretty sure if you run gdisk and create a GPT then it will convert the MBR into a protective MBR. You can see in gdisk when you first run it that the device has an MBR only. Then after running it you will see a GPT and a 'protective MBR'. As for what the exact difference between the two is, well, I'm not sure.

In any case the method we will use won't use a GPT. As far as I know only windows needs a GPT to boot from. Most linux-like systems will happily boot from a standard FAT32 partition without a GPT. I'm putting together an installer that I will pass on for testing. More challenging than I anticipated. :wall:
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Re: Uefi and porteus 3.0

Post#36 by donald » 17 Sep 2014, 22:30

--> protective mbr <--
This MBR defines exactly one partition that takes up the entire disk as unknown partition type.
This prevents that old operating systems and partitioning/mbr tools which do not support GPT,
can cause damage.
Therefore it is called "protective".. 8)

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Re: Uefi and porteus 3.0

Post#37 by brokenman » 18 Sep 2014, 02:11

Confirmed.
"The protective MBR is an MBR that defines a single partition entry (of type 0xEE) that covers the entire area of the disk used by GPT structures and partitions. It is designed to prevent GPT-unaware programs from accidentally modifying a GPT disk."
(Apple TN2166)
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Re: Uefi and porteus 3.0

Post#38 by Ed_P » 18 Sep 2014, 03:04

The MBR partition on my Porteus UEFI flash drive is not type 0xEE.

Code: Select all

D:\Users\Ed\My Utilities\MBRfix>mbrfix /drive 1 driveinfo
Drive 1
Cylinders = 948
Tracks (heads) per cylinder = 255
Sectors per track = 63
Bytes per sector = 512
Disk size = 7797565440 (Bytes) = 7 (GB)

D:\Users\Ed\My Utilities\MBRfix>mbrfix /drive 1 listpartitions
# Boot Size (MB) Type
1 Yes      7440   11  WIN95 OSR2 32-bit FAT
2             0    0  None
3             0    0  None
4             0    0  None


It is not Protected, not changed by Gdisk, when it read it in creating the GPT table, and thus not a hybrid. It is just a plain old simple MBR record, created by the Porteus install utility, that works allowing older OS systems to read my UEFI Porteus booting flash drive, like now on my Windows 7 machine. :Yahoo!:

And while I haven't tried it yet I suspect USB capable TVs will be able to read it also.
Ed

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