Allow rescue media to be created on a GPT disk


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Omoeba
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Since BIOS is largely obsolete, users should be able to create a rescue media on a GPT disk because a MBR disk is not necessary for UEFI.
Edited 12 December 2019 5:07 AM by Omoeba
jphughan
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Just for the sake of accuracy, even though laptops have been sold with UEFI support and UEFI OS installations for a few years now, BIOS is not "largely obsolete" by any stretch of the imagination -- especially among businesses and particularly on servers.  Businesses represent a major chunk of Macrium's customer base.  If you doubt this, notice that there's only one edition of Reflect targeted at individual users, while there are 3 for businesses -- plus the additional licensing options for the latter (Technician's License and System Deployment License), the ancillary management products such as Site Manager and MultiSite, and the option to subscribe to ongoing support that isn't available for the Home version.

Additional relevant data:
  • Macrium has said recently that they still have a large customer base running Server 2003, which uses the Windows XP kernel.  Those systems obviously use BIOS booting.
  • There is still a huge installed base of Windows 7 and Server 2008 R2, large enough that Microsoft is now offering businesses the option to purchase access to security updates for those OSes through the end of 2022.  Those OSes are almost always installed in Legacy BIOS mode because they don't take advantage of any UEFI capabilities, in fact they retain some Legacy BIOS dependencies even in UEFI mode, which means they don't work on a "pure UEFI" system.  The Windows 7 install media actually doesn't even support (partial) UEFI booting without manual modification.  The only reason to install those OSes in UEFI mode would be if you wanted an OS disk larger than 2TB, but that would be rare especially on those OSes.
  • While UEFI systems don't require MBR, they work with it just fine.
Concerns with supporting GPT targets:
  • The only meaningful use case for Rescue Media on a GPT disk would be if you wanted a Rescue Media partition on an external hard drive, but it is a dangerous practice to put your Rescue Media on a device that is always online.
  • If Rescue Media Builder supported targeting GPT disks, then if a user chose to build onto their external hard drive, they would see a prompt from Rescue Media Builder indicating that their external hard drive did not currently contain a suitable partition for Rescue Media and asking if they wanted to format their hard drive to resolve that.  The vast majority of users would not accept that, or worse, some users might click OK not realizing what was going to happen.  That is a large risk just to put Rescue Media somewhere that you arguably shouldn't put it in the first place.  And if you don't think users would accidentally erase their whole external hard drive this way, the recently released Reflect 7.2.4325 added a new checkbox that users had to tick to confirm that they wanted to overwrite their target disk/partitions during a clone or image restore operation before they could click Continue, because apparently the popup warning dialog saying that the specified partitions would be erased if users clicked Continue wasn't enough to stop some people.
  • If a user is technical enough to understand those risks and wants to do this anyway, then they are very likely technical enough to set up Rescue Media on a GPT device manually, which is already possible.  In fact the overwhelming majority of cases would require manual setup ANYWAY because again, an external hard drive out of the box isn't going to have a small FAT32 partition for Rescue Media.  So unless the user was ok having their whole drive wiped for Rescue Media Builder to set that up, they'd have to do it themselves.  The only people I can think of who might be ok with Rescue Media Builder wiping their disk are those who do this as soon as they get a new external drive, i.e. before putting any other data onto it.  But that won't be very many people.
When flash drives larger than 2TB become the norm, GPT support will be necessary.  But until then, adding support for GPT targets seems like it would introduce unnecessary risk, while only delivering a benefit to a small handful of people in a small number of use cases -- and again the benefit of having Rescue Media on an external hard drive is arguably a risk unto itself.


Edited 12 December 2019 8:28 PM by jphughan
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jphughan - 12 December 2019 4:13 PM
Just for the sake of accuracy, even though laptops have been sold with UEFI support and UEFI OS installations for a few years now, BIOS is not "largely obsolete" by any stretch of the imagination -- especially among businesses and particularly on servers.  Businesses represent a major chunk of Macrium's customer base.  If you doubt this, notice that there's only one edition of Reflect targeted at individual users, while there are 3 for businesses -- plus the additional licensing options for the latter (Technician's License and System Deployment License), the ancillary management products such as Site Manager and MultiSite, and the option to subscribe to ongoing support that isn't available for the Home version.

Additional relevant data:
  • Macrium has said recently that they still have a large customer base running Server 2003, which uses the Windows XP kernel.  Those systems obviously use BIOS booting.
  • There is still a huge installed base of Windows 7 and Server 2008 R2, large enough that Microsoft is now offering businesses the option to purchase access to security updates for those OSes through the end of 2023.  Those OSes are almost always installed in Legacy BIOS mode because they don't take advantage of any UEFI capabilities, in fact they retain some Legacy BIOS dependencies even in UEFI mode, which means they don't work on a "pure UEFI" system.  The Windows 7 install media actually doesn't even support (partial) UEFI booting without manual modification.  The only reason to install those OSes in UEFI mode would be if you wanted an OS disk larger than 2TB, but that would be rare especially on those OSes.
  • While UEFI systems don't require MBR, they work with it just fine.
Concerns with supporting GPT targets:
  • The only meaningful use case for Rescue Media on a GPT disk would be if you wanted a Rescue Media partition on an external hard drive, but it is a dangerous practice to put your Rescue Media on a device that is always online.
  • If Rescue Media Builder supported targeting GPT disks, then if a user chose to build onto their external hard drive, they would see a prompt from Rescue Media Builder indicating that their external hard drive did not currently contain a suitable partition for Rescue Media and asking if they wanted to format their hard drive to resolve that.  The vast majority of users would not accept that, or worse, some users might click OK not realizing what was going to happen.  That is a large risk just to put Rescue Media somewhere that you arguably shouldn't put it in the first place.  And if you don't think users would accidentally erase their whole external hard drive this way, the recently released Reflect 7.2.4325 added a new checkbox that users had to tick to confirm that they wanted to overwrite their target disk/partitions during a clone or image restore operation before they could click Continue, because apparently the popup warning dialog saying that the specified partitions would be erased if users clicked Continue wasn't enough to stop some people.
  • If a user is technical enough to understand those risks and wants to do this anyway, then they are very likely technical enough to set up Rescue Media on a GPT device manually, which is already possible.  In fact the overwhelming majority of cases would require manual setup ANYWAY because again, an external hard drive out of the box isn't going to have a small FAT32 partition for Rescue Media.  So unless the user was ok having their whole drive wiped for Rescue Media Builder to set that up, they'd have to do it themselves.  The only people I can think of who might be ok with Rescue Media Builder wiping their disk are those who do this as soon as they get a new external drive, i.e. before putting any other data onto it.  But that won't be very many people.
When flash drives larger than 2TB become the norm, GPT support will be necessary.  But until then, adding support for GPT targets seems like it would introduce unnecessary risk, while only delivering a benefit to a small handful of people in a small number of use cases -- and again the benefit of having Rescue Media on an external hard drive is arguably a risk unto itself.


Hi JP,

This is a very interesting reply. I very often learn something from reading your posts.I do not want to hijack this thread, but I would l like to make a side-step from the original topic (I do not see how I could do it differently).

You write "Those OSes are almost always installed in Legacy BIOS mode because they don't take advantage of any UEFI capabilities, in fact they retain some Legacy BIOS dependencies even in UEFI mode, which means they don't work on a "pure UEFI" system." I am curious whether you could elaborate just a bit more. I do know that Windows 7 does not support secure boot. The reason for asking is, first, that I am curious (I have learned everything about computers and Windows just by reading and trying). Second, because on one computer I have converted the Windows 7 x64 MBR installation to a UEFI installation using TeraByte OS Deployment Tool Suite which comes with Boot-It Bare Metal and has a script that does this in less than 30 seconds. The reason for doing so was that I could run Windows 7 from a 4TB drive. I would like to know if there are some aspects of this change which I should be aware of. F.i. I have never prepared a Windows 7 installation DVD for UEFI. Could that be an issue when needed, because the installation DVD also functions as a rescue DVD? A few years ago I have prepared an installation DVD with USB 3.0 drivers slipstreamed following detailed instructions I had found online, but that is the only time I did something like that. The converted UEFI installation has been working fine ever since I changed it from MBR a couple of months ago, with the exception that sometimes it could not come out of hibernation (Windows Resume Loader error). The solution to that was to set the motherboard to boot from UEFI only and not allow Legacy Option ROMs.

Thanks in advance for your answer.

Pim

Edited 12 December 2019 6:58 PM by Pim
jphughan
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Hey @pimjoosten

Happy to elaborate.  As you say, Windows 7 does not support Secure Boot, but it goes a bit further than that.  Windows 7 also requires that you keep UEFI CSM (Compatibility Support Module) enabled.  This option on Dell systems is called "Legacy Option ROMs", and it's worth pointing out that you cannot enable this without first disabling Secure Boot.  The normal reason you would enable that option on a UEFI system would be if you wanted to be able to freely switch between booting UEFI environments and Legacy BIOS environments without having to switch your BIOS configuration settings back and forth each time.  Whereas setting your system to Legacy boot mode disables UEFI boot support, and setting your system to UEFI mode without also enabling this option disables Legacy BIOS support, setting your system to UEFI mode with this option enabled allows it to support both boot modes simultaneously (albeit without Secure Boot).  Some systems automatically enable this UEFI CSM option if you disable Secure Boot, by the way.

Typically an OS that supports UEFI does not require UEFI CSM to enabled, even if it does not have a signed bootloader that would allow it to support Secure Boot.  Most Linux distros are like this, for example.  Windows 7 is not like that.  If you configure your system for UEFI boot, disable Secure Boot, and then also disable UEFI CSM/Legacy Option ROMs (assuming your system actually allows you to set this configuration), you will likely find that a Windows 7 UEFI installation will fail to boot, because it needs access to those Legacy Option ROMs even in UEFI mode.  At least that's been my experience.  This is why Windows 7 cannot be booted on a Hyper-V Gen 2 VM, even after disabling Secure Boot, because Hyper-V Gen 2 VMs are "pure UEFI", i.e. no access to UEFI CSM.  Quoting from this Microsoft article:

Q: Why are 64-bit versions of Windows Server 2008 R2 and Windows 7 not supported as generation 2 guest operating systems?
A: Although Windows Server 2008 R2 and Windows 7 support UEFI, they depend on a programmable interrupt controller (PIC), which is not present in generation 2 virtual machine hardware.


The practical impact of this is minimal, unless you want to install Windows 7 onto a disk larger than 2TB and your system doesn't allow UEFI CSM, in which case you're stuck.  But the end result is that the overwhelming majority of Windows 7 and Server 2008 R2 systems in use today are set up for Legacy BIOS booting, and since there are still a lot of those installations in the wild, it's difficult to argue that Legacy BIOS is obsolete.

Edited 12 December 2019 7:45 PM by jphughan
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Hi JP,

First of all my apologies for my late reply. I had to deal with some urgent issues first (a.o. a BSOD not related to Reflect) before I could write a reply.

Again very interesting information you have written. Thanks for that, I have learned something again. In your original reply to the OP you also wrote "The Windows 7 install media actually doesn't even support (partial) UEFI booting without manual modification.". However, I understood that installing Windows 7 by default supports a UEFI installation (see e.g. this MS blog post). Could you explain why you wrote that? Because of what you wrote I thought that using an installation DVD as a rescue medium could be problematic. I am curious whether that could be the case.

Thanks again,

Pim

jphughan
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The UEFI spec defines \EFI\boot\Bootx64.efi as a default bootloader file path. UEFI-bootable environments tend to have their bootloader file at that path because systems that use one-time boot menus will search devices for a bootloader file at that path to determine whether a given device contains a bootable environment. Of course it’s not mandatory to use that path in order to achieve UEFI booting (the Windows Boot Manager file used on Windows installations on hard drives doesn’t use that, for example), but if your bootable environment uses some other path, then it’s more work to get your UEFI system to boot from that environment. Windows Setup takes care of registering that non-standard path into the UEFI firmware, but you generally wouldn’t want to use a non-standard path on a flash drive because having to register a non-standard path to boot a temporary attached device would be a bit arduous.

Well....the UEFI bootloader file on default Windows 7 install media does not use the standard path. Its bootloader is located under (if memory serves) \EFI\Microsoft\Boot and it isn’t named Bootx64.efi. It’s an easy enough fix in that you just copy the file to the default folder and rename it, and now your USB Win7 media supports UEFI booting to the extent that Windows 7 can, but it’s not the default setup. DVDs and ISOs admittedly may be different because those entities have boot record pointers built into them. When you run the OSCDIMG tool included in the Windows ADK to create a bootable ISO from source files, one of the parameters you can specify is the path to the bootdata files for BIOS and UEFI booting, so the default path may not matter there. But I can’t test that because I don’t have any systems with optical drives anymore, and the only place I’d boot an ISO would be Hyper-V, which doesn’t support UEFI booting the Windows 7 kernel anyway for the reasons I mentioned above.

But if you can get it to start, then I see no problem using it as a rescue tool.
Edited 26 December 2019 4:01 PM by jphughan
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Thanks again for your reply. It was valuable information again. Most contributions on the internet (even the one from Microsoft I linked in my previous post) never discuss this issue. I had to do a thorough search to come up with the issue you described.

However, I was unable to start the DVD in UEFI mode after placing bootmgfw.efi in \efi\boot\ and renaming it to bootx64.efi or, as you suggested, copy the the bootloader to \efi\boot\. I have tried many different source variations of bootmgfw.efi from the various instructions I could find, but I could not get the DVD to be recognised as a UEFI bootable DVD. It just did not show up in the boot menu of the UEFI firmware. I even copied it from a Dell Windows 7 DVD which had \efi\boot\bootx64.efi on it, but that also did not work.

I was about to give up when I tried the solution mentioned in this thread by Milind R. I copied the files on the Windows 7 x64 DVD I already had made with slipstreamed USB 3.0 drivers to a folder on my hard drive. Then I entered the command "oscdimg.exe -h -m -o -u2 -udfver102 -bootdata:2#p0,e,bq:\win7dvd\boot\etfsboot.com#pEF,e,bq:\win7dvd\efi\microsoft\boot\efisys.bin -lWin7SP1x64_EN-US_XHCI_UEFI q:\win7dvd q:\win7.iso" and that worked! Strangely, this DVD does not have a \efi\boot\ folder, but that may have to do with what you wrote about specifying the path to the bootdata files.
I do not have a detailed idea what I did, but I roughly understand what this command did. I am certain I would understand it if I invested some more time, but I have already invested so much time that right now I am just happy it works.

So now I have a Windows 7 x64 DVD with USB 3.0 drivers which is bootable on both BIOS and UEFI systems! Smile

jphughan
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Hey Pim,

Glad you worked it all out! I guess I was confused by your earlier post. When you wrote that your understanding was that Win7 DVDs supported a UEFI installation by default, I thought you’d already found that a default, unmodified Win7 ISO from Microsoft boots successfully in UEFI mode. So I was trying to account for why that might be possible even if Win7 install media doesn’t support UEFI booting from a flash drive without modifications. Are you saying that’s not the case? That surprises me because Windows Setup itself DOES support performing a UEFI installation — meaning you don’t have to perform a manual command-line install to achieve a Win7 UEFI installation — as long as you boot into Windows Setup itself in UEFI mode. But then it does seem odd that the application would support a UEFI installation while by default the install media doesn’t actually allow being booted into UEFI mode from a disc or flash drive....

In any case, when you say you modified the files in the ISO, what command were you previously running to package the modified files into a new ISO? Or do you have some utility that allows you to just reach directly into an ISO and make changes? I always extract the files from an ISO, modify as needed, and then use OSCDIMG with the correct parameters to package those files up again. And yes, the fact that the EF bootdata path points in that command specifically to the EFISys.bin file means the bootloader path doesn’t have to be the default. Although come to think of it, even the notes for Win10 ISOs specify to point to that file at that location, so maybe the Bootx64.efi default path only applies when booting from disk storage? Not sure. Sorry!
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Hi JP,

There is a combination of many things that caused some misunderstandings, also on my side. In your post from December 12 you wrote: “The Windows 7 install media actually doesn't even support (partial) UEFI booting without manual modification.” Perhaps you only meant a flash drive, but I understood from your remark that DVD’s do not work on UEFI either. In my case I tried booting a DVD I had prepared myself in 2016, with USB 3.0 drivers added. And indeed, this DVD would not even show up in the UEFI boot menu. So my suspicion was confirmed that a Windows 7 DVD just does not boot in UEFI mode, even though MS said and I had assumed otherwise because Windows 7 itself runs fine in (non-pure) UEFI.

On the internet I found similar experiences, e.g. this one and this one. I then started looking what to do about it starting with your suggestion to make certain that there was a \efi\boot\bootx64.efi file. But that did not work, how hard I tried. I now assume that this modification is only necessary when booting from a USB (flash) drive.

In 2016 I had slipstreamed USB 3.0 drivers using Daemon Tools to edit the iso and then save it again. Because it was successful on my systems I thought this was the way to go. However, I had only been using it for MBR/BIOS systems and my current UEFI system was converted from a BIOS system, without the need for an installation disk. I now conclude that in order to get a bootable UEFI disk, I cannot use Deamon Tools, but must use oscdimg (I never knew about this program until you pointed me to it). I just tested the original Windows 7 DVD (X17-59463) that I used for adding the USB 3.0 drivers and that one does boot fine in UEFI. The modified iso/DVD does not, it only boots in BIOS mode. Is my assumption correct that UEFI has stricter requirements than BIOS?
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