Re: [gentoo-user] Dual booting Dell with Windows 7

[Peter Ruskin]

On Sunday 28 February 2010 23:51:21 Mick wrote:
> I have now succeeded at achieving what I wanted:  to use the
> Windows 7 boot manager (bootmgr.exe) which is the successor to
> NTLDR to chainload GRUB from it and so leave the Windows
> installation intact (at least until the warranty expires) ;-)
>
> I very briefly detail here the steps that I followed - if you
> need more please contact me and I will help if I can, or if I get
> some time I will sign up to edit a Wiki page.
>
> First the necessary WARNING:  You can render your MSWindows OS
> unbootable and without an installation CD things can get hairy.
>  So research the necessary steps to recover a borked MSWindows
> boot system using the facilities offered by the OEM *before* you
> start and use partimage to make a back up, just in case.
>
> There's two or three gotchas that make this more difficult than
> chainloading GRUB from NTLDR.exe under Win2k and WinXP:
>
> 1.  Disk and partition signatures in the MBR are used by Vista
> and Windows 7 to find the active boot partition of MSWindows.  If
> you move that partition then its disk offset changes and you
> start getting errors like "winload.exe..... is missing or
> corrupt", when what has actually happened is that the drive ID
> (partition signature) has changed and BCD doesn't know about it.
>
> 2.  OEMs use additional partitions to save installation images
> for recovery purposes and they often mark these as active boot
> partitions. The boomgr and BCD is consequently installed there as
> part of the installation script - but it doesn't clearly tell you
> this in the BCD file (that's the new boot.ini) unless you can
> decipher partition ID signatures.  Remove that recovery partition
> to save space and your MSWindows won't boot again.
>
> 3.  Windows 7 uses BitLocker on the IPL in the MBR and this may
> introduce additional complications - you mess with the MBR and
> then kiss goodbye to booting your MSWindows bloatware again.
>
> My solution worked by editing the BCD file using the native
> editor provided by MSWindows, the bcdedit command.  The
> winload.exe (which partly replaces NTLDR) is thereafter used
> normally to launch an image of the GRUB partition boot record and
> that of course knows where to jump to launch your Gentoo.
>  There's no need for 3rd party boot managers - there are two or
> three available like Neogrub which should do the same job by
> offering you a GUI, but if you are capable enough to install
> Gentoo then you can easily find your way around the BCD file with
> bcdedit.exe.
>
> The main steps to achieve this solution are:
>
> 1.  Install GRUB in your Linux /boot partition and capture an
> image of the partition boot record (it must be unmouted at the
> time):
>
> dd if=/dev/sda5 of=boot.lnx bs=512 count=1
>
> 2.  Copy the boot.lnx file to C:\boot.lnx
>
> 3.  Launch cmd.exe as administrator and call bcdedit /v which
> will show you something like this:
> ====================================================
> C:\Windows\system32>bcdedit /v
>
> Windows Boot Manager
> --------------------
> identifier              {9dea862c-5cdd-4e70-acc1-f32b344d4795}
> device                  partition=\Device\HarddiskVolume2
> path                    \bootmgr
> description             Windows Boot Manager
> locale                  en-US
> inherit                 {7ea2e1ac-2e61-4728-aaa3-896d9d0a9f0e}
> default                 {fda5ebf3-119b-11df-969c-f924691e8117}
> resumeobject            {5744906c-0bf4-11df-8e08-0026b920b49c}
> displayorder            {fda5ebf3-119b-11df-969c-f924691e8117}
>                         {fda5ebf6-119b-11df-969c-f924691e8117}
> toolsdisplayorder       {b2721d73-1db4-4c62-bf78-c548a880142d}
> timeout                 3
>
> Windows Boot Loader
> -------------------
> identifier              {fda5ebf3-119b-11df-969c-f924691e8117}
> device                  partition=C:
> path                    \Windows\system32\winload.exe
> description             Windows 7 Home Premium
> locale                  en-US
> recoverysequence        {5744906e-0bf4-11df-8e08-0026b920b49c}
> recoveryenabled         Yes
> osdevice                partition=C:
> systemroot              \Windows
> resumeobject            {5b312091-116a-11df-8b54-806e6f6e6963}
> ====================================================
>
> The first entry is the bootmgr, the second is MSWindows OS
> partition. First make a back up of the BCD file:
>
> C:\Windows\system32>bcdedit /export C:\BCD_backup
>
> Then create a new entry using bcdedit for the Linux boot image,
> by entering: ====================================================
> bcdedit /create /d "Gentoo Linux2" /application BOOTSECTOR
> The entry {fda5ebf7-119b-11df-969c-f924691e8117} was successfully
> created. ====================================================
>
> Cut and paste the partition ID in all the subsequent commands:
> ====================================================
> bcdedit /set {fda5ebf7-119b-11df-969c-f924691e8117} device boot
>
> bcdedit /set {fda5ebf7-119b-11df-969c-f924691e8117} path
> /boot.lnx
>
> bcdedit /set {fda5ebf7-119b-11df-969c-f924691e8117} locale en-US
> ====================================================
> If you don't get "The operation completed successfully." you know
> you've done something wrong.
>
> Then set it as last in the menu:
> ====================================================
> bcdedit /displayorder {fda5ebf7-119b-11df-969c-f924691e8117}
> /addlast The operation completed successfully.
> ====================================================
>
> and increase the delay before the menu automatically boots the
> default (leave the default as MSWindows until you prove that your
> Linux system can boot):
> ====================================================
>  bcdedit /timeout 10
> ====================================================
>
> Then run C:\Windows\system32>bcdedit /v to see what you have just
> made, at the bottom of the menu:
> ====================================================
> Real-mode Boot Sector
> ---------------------
> identifier              {fda5ebf6-119b-11df-969c-f924691e8117}
> device                  boot
> path                    \boot.lnx
> description             Gentoo Linux
> locale                  en-US
> ====================================================
>
> Now, this may not boot if your MSWindows boot drive is different
> to the MSWindows OS partition (as was in my case).  So, we need
> to point the bootmgr at the partition where the linux boot image
> resides, in my case C:
> ====================================================
> bcdedit /set {fda5ebf7-119b-11df-969c-f924691e8117} device
> partition=C: ====================================================
>
> Use the /v option to check all is good and reboot the machine.
> Hopefully, you will be greeted with a GRUB splash.  :-)

Thanks for the howto, Mick.  I followed it on my Windows Vista Home 
Premium 64; got "The operation completed successfully" all the way 
through, but on reboot I don't get a boot menu.

This doesn't matter much to me at the moment, as I use Acronis OSS 
Selector for boot manager, but this doesn't work on Windows 7, so 
my free update to Windows 7 is gathering dust.

-- 
Peter
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Gentoo Linux: Portage 2.2_rc63			kernel-2.6.32-gentoo-r5
AMD Phenom(tm) 9950 Quad-Core Processor		gcc(Gentoo: 4.4.3)
KDE: 3.5.10					Qt: 3.3.8b
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