Linux: How to backup hard disk partition table (MBR)

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Linux: How to backup hard diskpartition table (MBR)by nixCraft on July 10, 2006 · 12 comments· Last updated September 3, 2007

Linux: How to backup hard disk partition table ... http://www.cyberciti.biz/tips/linux-how-to-backup-...

1 of 9 03/27/2013 09:43 PM

If you don't want to take any chances with your data, it isrecommended that you backup hard disk partition table. LastFriday I was discussing some issues with one of our customerand he pointed out me dd command.

Backup MBR with dd command

dd the old good command which now backup partition tables even writes CDs ;).Backing up partition is nothing but actually backing up MBR (master bootrecord). The command is as follows for backing up MBR stored on /dev/sdX or/dev/hdX :# dd if=/dev/sdX of=/tmp/sda-mbr.bin bs=512 count=1

Replace X with actual device name such as /dev/sda.

Now to restore partition table to disk, all you need to do is use dd command:# dd if= sda-mbr.bin of=/dev/sdX bs=1 count=64 skip=446 seek=446

dd command works with Solaris, HP-UX and all other UNIX like operatingsystems. Read man page of dd for more info.

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{ 12 comments… read them below or add one }

1 Wartin April 15, 2010 at 1:37 pm

dd if= sda-mbr.bin

it has a blank space after =, it should read

dd if=sda-mbr.bin of=/dev/sdX bs=1 count=64 skip=446 seek=446

Reply

2 PT August 10, 2010 at 5:14 am

This advice does not work if you have an extended partition table.

Reply

3 VernDog January 26, 2011 at 4:26 pm

Wrong! This method DOES WORK with extended , primary partitions.I’ve used it all the time, to both backup & restore. Just remember tobackup MBR if you add any changes to partitions.

Reply

4 brendan December 1, 2012 at 11:29 pm

No. He’s right. The MBR lists whether a partition is active, itstype, start point and number of sectors within the partition. MBRlists this for a maximum of 4 partitions. This not include logicalpartitions. They are described within the extended partition.They are not described in the MBR.

Reply

5 Jack October 9, 2010 at 9:47 am


3 of 9 03/27/2013 09:43 PM

PT,

You can use sfdisk to backup extended partition table.

sfdisk -d /dev/sdX > backup-sdX.sf

Restore:

sfdisk /dev/sdX < backup-sdX.sf

Reply

6 jns August 22, 2011 at 6:07 am

The restore line corrupted my entire partition table…beware, i guess…

Reply

7 victor September 3, 2011 at 12:18 pm

jns, it could be because only one seek is needed.there are 446b of MBR, 64b of Partition Table and 2 as end (0x55aa). {=512b}if skip and seek aren’t synonimous, you seek 446 + 446.thus, command line must bedd if=sda-mbr.bin of=/dev/sdX bs=1 count=64 skip=446ordd if=sda-mbr.bin of=/dev/sdX bs=1 count=64 seek=446

Reply

8 victor September 3, 2011 at 12:45 pm

i’m sorry, i’m mistake. error coud be if mbr is all zero. then you must addconv=notrunc for no file optimization.ej:2GB filedd if=/dev/zero of=afile bs=1 seek=2GB count=1 (file size in hd<1kb)ordd if=/dev/zero of=afile bs=1 count=2GB (file size in hd=2gb)

size must be specific in bytes, 2gb is only for easy read.note: a little bs spend more time

Reply


4 of 9 03/27/2013 09:43 PM

9 Mr_T September 13, 2011 at 7:31 pm

Victor,In your first post, could you clarify the units you are using for mbr and thepartiton table and what is the “2 as end” means. Its not intuitive to theuninitiated.

Thanks

Reply


He’s talking about bytes. 446 bytes of Bootstrap code, then 4 partitionentries x 16 bytes = 64 bytes, then 2 bytes of signature (a 16 bitnumber = 0101010110101010). This is 55aa in hex and 21930 indecimal.

Reply


446 + 64 + 2 = 512 bytes :)

Reply

12 Marek December 7, 2011 at 11:19 am

What about GPT ?

Reply

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Linux: How to backup hard disk partition table (MBR)