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

The BCD Store

The Boot Configuration Data (BCD) Store contains all boot menu options and settings for Windows Vista (and later) operating systems. The BCD store is in a binary format and cannot be edited with a text editor - it can however be edited with the command-line BCDEdit tool (included with Windows Vista, Windows 2008, Windows 7, Windows 2012, Windows 8, Windows 8.1 and Windows 10).

A BCD store includes multiple entries - allowing for multiboot operating system setups. Even a basic setup with one Windows Operating System will have more than one entry, though they might not all be visible to the end user during the boot process. Entries in a BCD store (e.g. boot menu options) are classed as objects. Each object in the store will have its own globally unique identifier (GUID) value. All GUID values use the format {xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx} - where x is a hexadecimal digit. These values all contain 38 characters (including the braces ({ and }) and dashes (-)).

Each object in a BCD store will contain elements, which in turn contain data. See here for an example from a (BIOS) system with Windows 7 installed - this is displayed as bcdedit output. The following is one of the objects within this same BCD store (the operating system entry) -
Windows Boot Loader ------------------- identifier {4c1174e2-f3bc-11e4-b7bb-c026b235ee25} device partition=C: path \Windows\system32\winload.exe description Windows 7 locale en-US inherit {6efb52bf-1766-41db-a6b3-0ee5eff72bd7} recoverysequence {4c1174e3-f3bc-11e4-b7bb-c026b235ee25} recoveryenabled Yes osdevice partition=C: systemroot \Windows resumeobject {4c1174e1-f3bc-11e4-b7bb-c026b235ee25} nx OptIn
In this case the object has a guid of {4c1174e2-f3bc-11e4-b7bb-c026b235ee25} - the identifier. Each of the other entries are elements within the object -

• device
• path
• description
• etc

Entries within a BCD store are far more complex than the bcdedit output might indicate. As an example the data in the device element within the object above is displayed as partition=C:. The entry within the BCD store itself includes information about the disk signature and partition offset. The following REG_BINARY value illustrates this - the blue data is the partition offset (in bytes) and the red data is the disk signature -

BCD stores use the same format as Windows registry hives and can be mounted using regedit. When a BCD store is loaded as a registry hive we can see that each Object (identifiable by its GUID value) has its own Description and Elements subkeys. The Elements key contains further subkeys relating to different datatypes - e.g. the 12000004 subkey contains the Description for the object (the text that will appear in the boot menu).