Recovering NTFS boot sector on NTFS partitions
ID: Q153973
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The information in this article applies to:
-
Microsoft Windows NT Workstation versions 3.5, 3.51, 4.0
-
Microsoft Windows NT Server versions 3.5, 3.51, 4.0
SYMPTOMS
When a volume on a server or workstation becomes inaccessible or Disk
Administrator shows it as "unknown", you may have a corrupt or damaged
boot sector. This article will tell you how to find the second copy that
NTFS
stores and restore to the correct position on the disk.
Please keep in mind that two conditions must be met in order for this
information to apply to your issue:
- File system must be NTFS. FAT currently does not keep a copy of the
bootsector.
- You must be able to boot your machine to NT.
NOTE: If you cannot Boot into NT or move the drive to another NT machine
then follow Knowledge Base Article:
Q121517: How to recover from a corrupt NTFS bootsector
RESOLUTION
In order to resolve the problem, we need to retrieve the copy of the
backup bootsector and copy it back to the correct position on the Hard
Disk.
In NT 3.5x, the second copy is kept in the center of the logical volume
(Volume middle).
In NT 4.0, it has been moved to the end of the logical volume (Volume
end), which requires a different retrieval technique. The example shown
will be using Disk Probe (dskprobe.exe) for NT which ships on the NT V4.0
Resource Kit but will also run under NT V3.5x with the proper .dll files
installed.
Note:
To assure recovery during the following procedures, once you have verified
the NTFS boot sector and the copy to be valid, save the sector to a file
while viewing it by selecting "Save As" from the File menu and specify a
path and filename.
Recovering Bootsectors of Primary Partitions.
- Using Disk Probe choose DRIVES, Physical Drive. Select the
PhysicalDriveX where X = the ordinal of the disk. For example, Use Disk
Administrator to find what the ordinal is of the disk in question. For
example, if I have three SCSI disks in my system with SCSI ID's 1, 3, and
5, Disk Administrator will show them in order of 0,1,2. Furthermore, if I
remove disk with SCSI ID #3, SCSI Disk with ID #5 will move up to disk 1
and so on.
- Double click on the PhysicalDriveX you wish to repair. In the box
below, uncheck Read Only and press the Set Active button. You will then
notice that the Active Handle has been set to PhysicalDriveX, then select
OK.
- From the SECTORS Menu, select Read and insert 0 for STARTING SECTORS
and 1 for Number of Sectors, Click Read.
- You are now at the Master Boot Record (MBR) of your Physical disk. You
can verify this by the ASCII text on the right hand side beginning at
Offset 8B which should read "Invalid Partition Table....". From the VIEW
menu, select "Partition Table". From the box labeled "partition table
index", use the scroll bar to select the partition in question and double
click on that Partition. The Box in the lower, left-hand corner shows the
Relative Sectors, note this value (on the line provided below), and
Select the Tab "GO" next to this box.
Record RELATIVE SECTOR __________ value.
- Now from the VIEW menu, select "Bytes" so you can verify your position.
Depending on how the Bootsector has been corrupted, you can try to
identify some ASCII strings such as NTFS in the upper Right hand corner or
"A disk Read error occurred...", beginning at offset 130. From the VIEW
menu, select "NTFS bootsector". In this view, select the button, "Volume
End" for NT V4.0 or "Volume Middle" for NT V3.5x You should now be at
your backup copy of the bootsector. If you get an error stating
"incomplete Data Read" or after examining the bytes, determine this is not
the backup copy of the bootsector, your primary bootsector was corrupt so
that the values we needed to Jump to the backup copy were incorrect.
Please go ahead to the next section showing how to recover the bootsector
when it is missing or heavily corrupted, otherwise continue with step 6.
- From the VIEW menu, select Bytes and verify that this is the NTFS
bootsector. Once verified, From the SECTORS menu, select Write, make sure
the dialog box shows the correct Handle and PhysicalDrive. In box
Starting Sector to write Data, type in the number of Relative sectors you
noted in step #4 and select the Button Write it.
- Go to the SECTORS menu and type in the Relative sector from step #4
while keeping Number of sectors to 1, select Read. Here, please verify
that the data was written.
- Close Disk Probe and reboot your system.
Recovering Backup bootsector if original copy is missing, heavily
corrupted, or does contain any usable data.
If the bootsector is missing or corrupted in such a manner that the
information in the Primary Boot sector pointers were incorrect, usually
the number of sectors are wrong, use the following steps to recover.
- Using Disk Probe choose DRIVES, Physical Drive. Select the
PhysicalDriveX where X = the ordinal of the disk. For example, Use Disk
Administrator to find what the ordinal is of the disk in question.
- Double click on the PhysicalDriveX you wish to view. In the box below,
uncheck Read Only and select the button Set Active. You will then notice
that the Active Handle has been set to PhysicalDriveX, then select OK.
- From the SECTORS Menu, select Read and insert 0 for STARTING SECTORS
and 1 for Number of Sectors, Click Read.
- You are now at the MBR of your Physical disk. You can verify this by
the ASCII text on the right hand side beginning at Offset 8b which should
read "Invalid Partition Table....". From the VIEW menu, select view
Partition Table. Select the correct partition number which is in
question.
- We will need two values; Total Sectors, Relative sectors. Please note
the Relative sectors value since this is where the bootsector should be
located. To find the backup copy of the bootsector, perform the following
calcualtion:
Record Total Sectors: _________
Record Relative Sectors: _________
EXAMPLE #1: FOR NT V4.0 WHERE THE BACKUP COPY IS AT THE END OF THE
VOLUME:
Total Sectors --> 1062880
+ relative Sectors --> 32 +
---------
1062912
- Minus one sector --> 1 -
---------
Backup bootsector --> 1062911
EXAMPLE #2: FOR NT V3.5x WHERE THE BACKUP COPY IS IN THE MIDDLE OF THE
VOLUME:
Total Sectors --> 1062880
Divided by 2 --> 531440
+ relative Sectors --> 32 +
---------
Backup bootsector --> 531472
- Select SECTORS, Read and input Starting sector as the value calculated
in Step #5, Number of sectors to 1. Select Read and you should be at the
location of your backup bootsector.
- From the VIEW menu, select Bytes and verify that this is the NTFS
bootsector. Once verified, from the SECTORS menu, select Write, make sure
the dialog box shows the correct Handle and PhysicalDrive. In box
Starting Sector to write Data, type in the number of Relative sectors you
noted in step #5 and select the Buttion Write it.
- Go to the SECTORS menu and type in the Relative sector from step #5
while keeping Number of sectors to 1, select Read. Here, please verify
that the data was written.
- Close Disk Probe and reboot your system.
Recovering Bootsectors of extended partitions:
- Using Disk Probe choose DRIVES, Physical Drive. Select the
PhysicalDriveX where X = the ordinal of the disk. For example, Use Disk
Administrator to find what the ordinal is of the disk in
question.
- Double click on the PhysicalDriveX you wish to view. In the box below,
uncheck Read Only and select the button Set Active. You will then notice
that the Active Handle has been set to PhysicalDriveX, then select OK.
- From the SECTORS Menu, select Read and insert 0 for STARTING SECTORS
and 1 for Number of Sectors, Click Read.
- You are now at the MBR of your Physical disk. You can verify this by
the ASCII text on the right hand side beginning at Offset 8b which should
read "Invalid Partition Table....". From the VIEW menu, select view
Partition Table. Select VIEW , As Partition Table.
- In this view, in the Partition Table Index box, select your partition
that contains your Extended partition. Once done, the System ID box
should read "Extended". If the partition in question is the fourth
logical drive in the Extended partition, click the Next partition button 4
times. The System ID box should now read "NTFS"
- At this point, in the Partition Table Index box, select (double-click)
your partition that contains your Extended partition. Once done, the
System ID box should read "Extended."
Now, navigate to the logical volume that needs repair within the extended
partition. If the damaged volume is the second volume in the partition,
click the "Next Partition" button twice. As you navigate through volumes
in the extended partition, the System ID field should indicate the file
system
of each partition.
Once you have found the partition that needs repair, record the current
sector (from the title bar of Disk Probe), the relative sector, and total
sectors of this volume. This information will be used to calculate the
location of the backup copy of the boot sector.
Current Sector ________________________
Relative Sector _______________________
Total Sectors _________________________
Click the Go button to go to the boot sector of the damaged volume. Note
the location of this sector from the title bar.
Boot Sector ___________________________
To verify that you are looking at the correct sector, Select Bytes from
the View menu. If the sector has only minor damage, you should see ASCII
error text in the right hand column. (If the sector has been completely
overwritten, you won't have this assurance.)
Note this location so we know where to copy the backup bootsector.
Current sector __________
Relative sectors __________
Total Sectors __________
- To find the backup copy, you will need three values, Relative Sectors,
Total Sectors, and Current sector which you noted in step #6. Perform the
following calculation using your values:
EXAMPLE #1: FOR NT V4.0 WHERE THE BACKUP COPY IS AT THE END OF THE
VOLUME:
Current sector: 819200
Total Sectors: 243680 +
======
1062880
Relative Sectors 32 +
======
1062912
Less one 1 -
======
Backup Bootsector 1062911
EXAMPLE #2: FOR NT V3.5x WHERE THE BACKUP COPY IS IN THE MIDDLE OF THE
VOLUME:
Current sector: 819200
+ Total Sectors: 243680 divided by 2 : 121840 +
======
941040
+ Relative Sectors 32 +
======
Backup Bootsector 941072
- Select SECTORS, Read and input Starting sector as the value calculated
in Step #7, Number of sectors to 1. Select Read and you should be at the
location of your backup bootsector.
- From the VIEW menu, select Bytes and verify that this is the NTFS
bootsector. You should see ASCII error text in the right hand column. If
this sector does not appear to be a valid boot sector, do not continue.
Start the process over and find the correct sector that contains the
backup copy o
the bootsector.
Once you have verified that this is the backup copy of the bootsector,
write this sector to the location of the original boot sector you
discovered in step 6. From the Sectors menu, select Write. Make sure the
dialog box shows the correct Handle and PhysicalDrive. In the Starting
Sector box, enter the location of the original bootsector. Click "Write
it" to write this information to the disk.
- Go to the SECTORS menu and select Read. In the starting sector, type
in the Sector to which you wrote the backup copy, while keeping Number of
sectors to 1. Select Read, and verify that the data was written.
- Close Disk Probe and reboot your system.
Norton Diskedit is manufactured by Symantec Corporation, a vendor
independent of Microsoft; we make no warranty, implied or otherwise,
regarding this product[ASCII 146]s performance or reliability.
Additional query words:
prodnt
Keywords : kbother ntfault ntfilesys NTSrvWkst
Version : 3.5 3.51 4.0
Platform : winnt
Issue type :
Last Reviewed: February 25, 1999