Index Introduction The BCD Store The System BCD Store Default Paths\Setup (BIOS) Default Paths\Setup (UEFI) BCDEdit - The Basics Check Entries in a BCD Store Devices Devices - locate Backing up the BCD Store Examples - Part 1 Examples - Part 2 Examples - Part 3 Examples - Part 4 BCDEdit Commands BCDEdit Versions Mounting the BCD Store... Acknowledgements Appendices ========= Glossary BCDEdit (version 6.0.6001) BCDEdit (version 6.1.7601) BCDEdit (version 6.3.9600) Device Partition - Data Objects and Elements Alternatives to bcdedit UEFI, BIOS, GPT and MBR

Devices

This section looks at the syntax used for devices and file paths. The following information has been copied from the (Windows 8.1) bcdedit.exe help topic for FORMATS (run command bcdedit.exe /? FORMATS [enter]). Please note that these device types may not be supported in other versions of bcdedit.

.... A device can be one of the following types: BOOT PARTITION=<drive> HD_PARTITION=<drive> FILE=[<parent>]<path> RAMDISK=[<parent>]<path>,<optionsid> VHD=[<parent>]<path>,<locatecustom> LOCATE[=<locatecustom>] The options for these types are: <drive> A drive letter with a colon and no trailing backslashes. <parent> (Required) Can be either BOOT, LOCATE, or a drive letter with colon. The square brackets do not indicate that this is optional, but are a literal part of the syntax. <path> A path to the file (or .wim file) from the root of the parent device. <optionsid> The identifier to the device options entry that contains the system deployment image (SDI) options for the RAM disk. This is usually {ramdisksdioptions}. <locatecustom> Supplies an optional element used to locate a device by looking for a specified path. The default locate element for a device is its application path (systemroot for an osdevice). Custom values must be specified using custom element syntax (see -help types customtypes), for example: locate=custom:22000002.

The following sections expand on the Device types used in BCD Stores -

• Boot
• Partition
• HD_Partition
• VHD
• Locate
• Unmounted Partitions
• Example

Boot

Using the BOOT device type will specify the boot drive is used as a relative path for corresponding elements in the object - this will be the drive from which the Windows Boot Manager (BOOTMGR on BIOS systems or bootmgfw.efi on UEFI systems) is loaded.

On partitioned storage devices (e.g. a hard disk drive) using BOOT as the device type for the element will specify the use of the partition from which the Windows Boot Manager is loaded. Assuming a default Windows setup is used this will be the active primary partition on the first hard disk (BIOS systems) or the EFI System Partition (UEFI systems).

Unlike some of the other device types (e.g. partition=) setting the device as boot will not lock the entry to a particular device or system as unique drive and partition information is not used - paths are relative to the Windows Boot Manager. This potentially allows for the use of a generic BCD store providing that certain restrictions are met - the operating system being loaded must be on the same partition as the Windows Boot Manager and BCD Store. This has very limited application and will be of little use on multiboot systems. The use of a generic BCD Store is discussed in the Create a Windows System From Scratch Using Linux topic on the reboot.pro forum.

Setting the device as boot is particularly useful when cloning a system - using the Sysprep tool in Windows Vista will change device paths as boot for example.

Partition

Using a drive letter (e.g. Partition=C:) will create an entry in the BCD store containing information unique to the disk and partition specified.

• On systems with BIOS firmware, the data will contain disk signature and partition offset information.

• On systems with UEFI firmware, the data will contain the disk GUID and partition GUID information - these GUID values should not be confused with GUID values used for BCD objects.

Note - the appendices includes a more detailed look at the element data in Partition type Devices (see here).

HD_Partition

In my brief tests there does not appear to be any difference between using HD_PARTITION or PARTITION device types. Specifying HD_PARTITION on the bcdedit.exe command line (e.g. bcdedit.exe /set {bootmgr} device HD_PARTITION=C: [Enter]) returned the following output when the bcdedit.exe /enum [Enter] command was used to check the entry -
Windows Boot Manager -------------------- identifier {bootmgr} device partition=C:

VHD

The VHD device can be used to boot a VHD type image file containing a Windows Operating System - this is referred to by Microsoft as Native Boot VHD.

VHD device types must specify a parent device type (either Partition, Boot or Locate) followed by the path to the .vhd file - path is relative to the device root. E.g. -

• bcdedit /set {GUID} device vhd=[C:]\Windows7.vhd [enter]
• bcdedit /set {GUID} device vhd=[boot]\Windows7.vhd [enter]
• bcdedit /set {GUID} device vhd=[locate]\Windows7.vhd [enter]

Locate

Windows 7 introduced a new device type - locate. This can be used to scan drives for a path that has been set in another element within the same Object. Using locate is covered elsewhere in these notes (see here).

Unmounted Partitions

A drive letter can be substituted with a \Device\HarddiskVolume# entry if the drive has not been mounted - where # is a numeric value starting from 1. This is not recommended if multiple devices are attached to the system as it can be complicated to predict the volume number.

Example

Assuming we wanted to add a menu entry to boot WinPE from the first partition on hard disk zero (partition is mounted as C: drive and is the boot partition containing BOOTMGR and the BCD store) we could use any of the following commands -

• bcdedit /set {GUID} device ramdisk=[boot]\Boot\boot.wim,{ramdiskoptions} [enter]

• bcdedit /set {GUID} device ramdisk=[C:]\Boot\boot.wim,{ramdiskoptions} [enter]

• bcdedit /set {GUID} device ramdisk=[\Device\HarddiskVolume1]\Boot\boot.wim,{ramdiskoptions} [enter]