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Thread: How to boot from Virtual Hard Disk?

  1. #1
    Join Date
    Jul 2010
    Posts
    15

    How to boot from Virtual Hard Disk?

    Hi friends, I am having doubt on booting from VHD (Virtual Hard Disk), so thought that you guys will provide some help for me. I am having some basic knowledge about the VHD, so you can consider me as noobie. The support of booting from VHD is one of innovation in Windows 7 that inspires me most. All, for example, as I have regularly demo computer to reset to a defined level and looking to exploit all technical possibilities of the local hardware are no longer (for example, multi-touch, UMTS modem, etc.) are past it. Now the thing I am interested is knowing about the booting. Please provide me some useful notes about the booting that can be done from virtual hard disk. Also I am expecting some detailed information (since I am noobie, ) from your side. It would be really very grateful if you explain me with the chart (or figure) about the VHD.

  2. #2
    Join Date
    Oct 2008
    Posts
    80

    Re: How to boot from Virtual Hard Disk?

    VHD stands for Virtual Hard Disk and is open as a container format, which was used for the virtual machines operate so far. With Windows 7, the boot manager extended so that you reinstall the operating system, device drivers and required software is no longer mandatory on the local hard disk, but can instead use a VHD container. So you can from virtualization as Differencing Disks with a local installation to use functions. These were some basic things that you should aware about. According to me, you should know all these things before moving forward deep in concepts. So I am hoping that I had helped you to some extent.

  3. #3
    Join Date
    Oct 2008
    Posts
    117

    Re: How to boot from Virtual Hard Disk?

    To understand how the boot from VHD, we look first to the normal boot process. In summary outlines the following:
    1. When the computer starts, the BIOS initializes the hardware and loads the Master Boot Record (MBR) on sector 0 of the hard drive.
    2. The MBR loads the boot manager of the operating system.
    3. The boot manager allows the user to select various boot options.
    4. Discretion of the user or after a timeout of the boot manager to the preferred boot loader loads the appropriate options.
    5. The boot loader in turn loads the system configuration and necessary files for booting the operating system (kernel, HAL, boot drivers, etc.).
    6. After all the boot files are loaded into memory, the boot loader passes control to the loaded kernel.
    7. The kernel initializes all the boats provided for drivers and loads the rest of the operating system.
    Now in order to boot from a VHD instead of a local hard disk partition, this process needs to be changed slightly. The VHD boot process works in the boot manager and boot loader as a filter for all file access (file block IO). Whenever such access is detected, this is not done directly to the hard disk but passes through a filter that checks whether the goal of access is a valid VHD. Should be the way forward for all the filters on reading, writing and closing operations in the VHD.

  4. #4
    Join Date
    Mar 2008
    Posts
    382

    Re: How to boot from Virtual Hard Disk?

    Whenever such access is detected, this is not done directly to the hard disk but passes through a filter that checks whether the goal of access is a valid VHD. Should be the way forward for all the filters on reading, writing and closing operations in the VHD.
    Here, the filter boat reads and writes converted from the logical offset to a physical offset within the VHD file, performs the operation in the physical VHD file and returns the result to the calling instance. If access is closed to the VHD file, releases all resources allocated by then again. Basis to access the virtual SCSI miniport driver is vhddisk.sys. He is the first phase of the boot process in 5 started. If all the boat drivers have been initialized vhddisk including, without prejudice to the kernel to the boot loader information that in 4th were determined. It can now detect whether the boot process to take place of a VHD file.

  5. #5
    Join Date
    Apr 2009
    Posts
    107

    Re: How to boot from Virtual Hard Disk?

    If that's the case, the kernel extracted the full path to the VHD file and sends an IOCTL command to vhddisk with the task of integrating the VHD file in the system. Here's a little chart:


    By including the VHD file is now represented as a SCSI hard disk to the system over. After the process is complete, the operating system treats the newly added disk as a regular SCSI drive and the boot process is running, as usual, then.

  6. #6
    Join Date
    Feb 2009
    Posts
    62

    Re: How to boot from Virtual Hard Disk?

    An existing VHD file to the boot manager of Windows 7 to take time, enter from an administrator command line:
    bcdedit / {guid} device vhd = [locate] \ set windows7.vhd
    bcdedit / {guid} osdevice vhd = [locate] \ set windows7.vhd
    If the hardware environment brings about a change and had generalized to the installation in the VHD with Sysprep, you should turn on the recognition of the HAL on the next boot the VHD:
    bcdedit / set {guid} detecthal on
    However, it is also an already existing installation to extend the Windows 7 boot manager to integrate it VHD file as a boot device. The easiest way from a main memory in the loaded Windows PE version. But enough to boot from a Windows 7 installation source. There, you go to the computer repair options and open a command line options. Here you go then:
    1. Copy the VHD file on the local hard disk:
      copy y: \ windows7.vhd c: \
    2. Temporary integration of the VHD file as a drive:
      diskpart
      select vdisk file = c: \ windows7.vhd
      attach vdisk
      assign letter = v
      exit
    3. Copy the boot environment of the VHD file and the Boot Configuration Data (BCD) configuration with Bcdboot from the \ Windows folder of the VHD to the physical system partition. For PCs with a standard BIOS that is the active partition on the first hard disk:
      cd / dv: \ windows \ system32
      bcdboot v: \ windows
    BCDboot automatically import the existing configuration and boot into the menu. Then you integrate the VHD in the boot menu as was already stated.

  7. #7
    Join Date
    Feb 2006
    Posts
    126

    Re: How to boot from Virtual Hard Disk?

    If you want to create a custom installation, can make directly in Windows 7 or Windows Server 2008 R2. (. Wim) Just in Disk Manager and create a VHD file with imagex (found in WAIK) the desired operating system from a Windows installation image to use:
    imagex / apply <pathtowim> 1 r: \
    On the computer technician, use the Diskpart tool to create, attach, partition, and format a new virtual hard disk. You can attach a VHD by using the Attach vdisk Which command adds the. Vhd file as a disk to the storage controller on the host. This virtual disk will appear as the R: drive at the end of this procedure. The detach command will stop this virtual disk from appearing on the host. The Windows AIK is ideal for highly customized environments. The tools provide facilities for AIK in numerous deployment options and a high degree of flexibility. The deployment environment is different from company to company. Their business needs and resources determine whether you use all available resources in the AIK or use only a part of it. For Windows 7-beta version of the Windows AIK documentation in CHM format is available only as part of the Windows AIK tools.

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