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Windows 7: BCDEDIT - How to Use



BCDEDIT - How to Use

How to Use the BCDEDIT Command Line Tool
Published by limneos
22 Jan 2009
Published by

How to Use the BCDEDIT Command Line Tool

information   Information
This will show you how to use BCDEDIT in the command prompt and avoid the need of third party applications like EasyBCD.
Note   Note
Bcdedit is a really powerful tool that Windows Vista and Windows 7 uses to manage the boot loader entries.

BCDEDIT needs a boot manager to boot your system.


A boot manager is a file that contains necessary information that instruct the system how to boot/start an operating system.
  • Windows 7 and Vista boot manager file is \bootmgr
  • Windows XP boot manager file is \ntldr
BCDEDIT can support other boot managers too, like grub for linux. You just have to place the boot file on the root of the boot manager partition. e.g. \grldr and you have a grub boot loader enabled.

Bcdedit edits a file called bcd , which is located in Windows 7's hidden partition under \boot\bcd.
In Vista, its located under C:\boot\bcd.


warning   Warning
You must be logged on in an administrator account to be able to do this tutorial.





To Use bcdedit:
1. Open an elevated command prompt.

2. Type bcdedit and press enter.
NOTE: By typing just bcdedit you just list your boot entries.


A boot entry consists of 4 main elements:
1. Identifier
The identifier is how the system has named the boot entry.
2. Device
The device is the drive or virtual image that the system will use to boot the boot entry.
3. Path
The path is the location on the device where the bootloader file is found.
4. Description
The description is the friendly name we give to our boot entry, e.g. "Windows 7"
You see next to the identifiers their UUIDs in {}. The UUID is the unique codename that the system gives to each boot entry and cannot be changed.

The standard identifier UUIDs are explained below:
{bootmgr} = the boot manager
{current} = the OS you selected to boot at startup.
{default} = the default OS selected to boot the PC.
{ntldr} = Windows Legacy OS Loader (for windows xp)
there are others like {memdiag} or {ramdisk} but they can't be of much use right now.
warning   Warning
IMPORTANT: make a backup of your bcd file first. To do that, type:

bcdedit /export C:\SAVEDBCD

This will create a file c:\savebcd which is your boot entry backup.
If you mess up, you can always undo changes by:

bcdedit /import c:\savedbcd



Now to see how we can control the above entries, here are some examples:
bcdedit /set {current} description "My edited Windows Boot Entry"
NOTE: This changes the title of the boot menu entry "{current}".

bcdedit /set {ntldr} device partition=E:
NOTE: This tells bcd that Windows XP partition is drive E:

bcdedit /set {ntldr} path \ntldr
NOTE: This tells bcd that the ntldr file which is the winxp bootloader is on root folder "\" (of drive e: as stated above)

bcdedit /displayorder {ntldr} /addfirst
NOTE: This places Windows XP as the first OS on the menu list.

bcdedit /default {ntldr}
NOTE: This places Windows XP as the default OS to boot first with.

bcdedit /displayorder {33342343-3424-2342342342-2344} /addlast
NOTE: This tells bcd that the boot entry with UUID 3334... should be the last entry on the menu.
You can copy your existing VISTA or Windows 7 boot entry to another identical. Then you can change settings on the new entry to experiment. You will always have the first entry available, so it's safe to play with.
bcdedit /copy {current} /d "New Windows 7 boot entry I just copied!"
this will give you a line:
NOTE: The entry was successfully copied to {4c21825f-e04b-11dd-b760-00195b61617a}. The {4c21825f-e04b-11dd-b760-00195b61617a} is the UUID of the new entry that the system just created. Yours will be different than mine! This is its identifier and you should use this to address that entry. Example:

bcdedit /set {4c21825f-e04b-11dd-b760-00195b61617a} numpoc 2
NOTE: This adds the 2 CPU Core support during boot, like you do in msconfig.

bcdedit /deletevalue {4c21825f-e04b-11dd-b760-00195b61617a} numproc
NOTE: This deletes the numproc parameter from entry {4c21825f....}

bcdedit /delete {4c21825f-e04b-11dd-b760-00195b61617a}
NOTE: This deletes the boot entry {4c21825f....} completely. In order to delete an {ntldr} entry, you must use the /f switch to force deletion: bcdedit /delete {ntldr} /f

You can always type just bcdedit to see your current settings.

What else can I do with BCDEDIT?

You can use BCDEDIT to alter any boot parameter , like you would in msconfig, only more. BCDEDIT works from booting with installation dvd too, so it can be handy for recovery purposes.
bcdedit /timeout 5
NOTE: This sets the wait-to-select-OS menu timeout at startup to 5 seconds . You will notice that I didn't give a UUID above. If you omit the UUID, it applies automatically to the relavant UUID. So: bcdedit /timeout 5 is identical to bcdedit /set {bootmgr} timeout 5
Some more advanced examples:
bcdedit /set {current} detecthal yes
bcdedit /set {current} detecthal no
NOTE: The above commands sets the detecthal to yes or no for entry {current}
To create a new boot entry to load Windows XP from a partition on your disk:
NOTE: The example below uses F: as the Windows XP partition. Replace with your xp drive letter.
bcdedit /create {ntldr} /d "Windows XP"

bcdedit /set {ntldr} device partition=F:

bcdedit /set {ntldr} path \ntldr

bcdedit /displayorder {ntldr} /addlast
Note   Note
Final note: BCDEDIT works from installation boot dvd too. If you mess up with a setting and you cannot boot, just boot from DVD and enter Repair Computer, then go to command prompt and there you go. You can play again with bcdedit to restore your system back.




[/INDENT]
.

22 Jan 2009   #1
garysgold

Vista Ult 64 bit Seven Ult RTM x64
 
 

Saw this in the thread first. Thanks much.

Gary

My System SpecsSystem Spec
.

22 Jan 2009   #2
SIW2

Microsoft Community Contributor Award Recipient

Vista x64 / 7 X64
 
 

Hi,

Nice and clear Limneos.

Easy bcd and VistaBootPro are very handy for many things, tho. it is good for people to have some bcdedit knowledge - particularly if they need to use the boot dvd.

More detail here :

Recovering the Vista Bootloader from the DVD - NeoSmart Technologies Wiki

Hope it helps

SIW2
My System SpecsSystem Spec
22 Jan 2009   #3
Bare Foot Kid
Microsoft MVP

W 7 64-bit Ultimate
 
 

Hello limneos.

Thank you very much; I haven't had time to go through the tutorial yet, but I will. I was going to suggest you do a proper tutorial as we are having many requests for this knowledge and I will be sure to point people to this tutorial first, in future.

Thanks again.












Later Ted
My System SpecsSystem Spec
11 Mar 2009   #4
SteveB

XP or Win7 (preferred!)
 
 
Help! Trapped in "safe" mode, just learning BCDEDIT...

Folks,

I made the mistake of selecting "safe mode" boot from my gui screen earlier this morning. I don't even know where... I was hunting for why I wasn't properly joining my work domain (1st Windows 7 beta in the domain!) and selected safe boot and now I can't get back to my "normal" Windows 7 boot.

I have tried from elevated-cmd to "bcdedit /set safe off" or some such but I haven't got the right combo yet.

Can anyone tell this BCDEDIT newby what the proper command is?

Tanks In Advance! ...Steve (waiting in safe land, want my Windows 7 back!)
My System SpecsSystem Spec
11 Mar 2009   #5
SIW2

Microsoft Community Contributor Award Recipient

Vista x64 / 7 X64
 
 

Hi Steve,

Type msconfig in Start search box - click it when it pops up.

Click Boot tab - uncheck Safe Boot , Apply, OK. Restart

Hope it helps.
My System SpecsSystem Spec
11 Mar 2009   #6
SteveB

XP or Win7 (preferred!)
 
 

SIW2,

As a pun (per your pic), you "made my day"!

I'm not sure that I did exactly as you suggested but at the safe mode command line prompt I typed "msconfig" which gloriosky! brought it up and I clicked on the "boot" tab, unselected safe and debug log and then rebooted.

Voila! My Windows 7 GUI is making me happy again... I owe ya, big fella! Thanx...SteveB
My System SpecsSystem Spec
11 Mar 2009   #7
SIW2

Microsoft Community Contributor Award Recipient

Vista x64 / 7 X64
 
 

You're welcome
My System SpecsSystem Spec
28 Mar 2009   #8
PhoneyVirus

Windows 7 Professional (64-bit)
 
 

If I'm reading this right to edit the Windows XP description from "Earlier Version of Windows" to say "Windows XP Home" or to what ever you want. Would be the following bcdedit /set {ntldr} description "Windows XP Home"

For bcdedit /displayorder {ntldr} /addfirst
NOTE: This places Windows XP as the first (default) OS on the menu list.

To put back Windows 7 as the (default) OS would be the following
bcdedit /displayorder {current} /addfirst

For Windows XP This is how your OS Loads

When you turn on your computer, it goes through an elaborate startup process. The process begins when your computer performs its power-on self test (POST), which is followed by the POST for each adapter card that has a BIOS, such as SCSI adapters and video cards. The system BIOS then reads the master boot record (MBR)—the first sector on the first hard disk—and transfers control to the code in the MBR, which is created by Windows XP Setup.

This is where Windows takes over the startup process. Here’s what happens next:

1. The MBR reads the boot sector—the first sector of the active partition—which contains code that starts Ntldr, the bootstrap loader for Windows XP. The initial role of Ntldr is to switch the system to protected mode with paging enabled to allow full memory addressing, start the file system, read the Boot.ini file, and display the boot menu. Note that Ntldr must be located in the root folder of the active partition, along with Ntdetect.com, Boot.ini, Bootsect.dos (if you’re going to dual boot), and Ntbootdd.sys (if you’re using certain SCSI adapters for the drive with the boot partition).

2. If you select Windows XP from the boot menu, Ntldr runs Ntdetect.com to gather information about the currently installed hardware. Ntldr then uses the Advanced RISC Computing (ARC) path specified in Boot.ini to find the boot partition—the one where Windows XP is installed—and loads the two files that constitute the Windows XP core: Ntoskrnl.exe and Hal.dll. Both files must be located in the %SystemRoot%\ System32 folder.

3. Ntldr continues by reading the files that make up the registry, selecting a hardware profile and control set, and loading device drivers.

4. At this point, Ntoskrnl.exe takes over and starts Winlogon.exe, which in turn starts Lsass.exe (Local Security Administration), the program that displays the Welcome screen (or the Windows logon dialog box) and allows you to log on with your user name and password.

Please Rep!
My System SpecsSystem Spec
29 Mar 2009   #9
PhoneyVirus

Windows 7 Professional (64-bit)
 
 
Change the OS Name in Windows Boot Manager

I found it on the Vista Forums


If I helped solve your time give me some Rep! Thanks



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