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

If you don’t want to take any chances with your data, it is recommended that you backup hard disk partition table. Last Friday I was discussing some issues with one of our customer and 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 boot record). 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 operating systems. Read man page of dd for more info.


man dd

dd – convert and copy a file


Copy a file, converting and formatting according to the operands.

force ibs=BYTES and obs=BYTES

convert BYTES bytes at a time

convert the file as per the comma separated symbol list

copy only BLOCKS input blocks

read BYTES bytes at a time

read from FILE instead of stdin

read as per the comma separated symbol list

write BYTES bytes at a time

write to FILE instead of stdout

write as per the comma separated symbol list

skip BLOCKS obs-sized blocks at start of output

skip BLOCKS ibs-sized blocks at start of input

suppress transfer statistics

BLOCKS and BYTES may be followed by the following multiplicative suffixes: xM M, c 1, w 2, b 512, kB 1000, K 1024, MB 1000*1000, M
1024*1024, GB 1000*1000*1000, G 1024*1024*1024, and so on for T, P, E, Z, Y.

Each CONV symbol may be:

ascii from EBCDIC to ASCII

ebcdic from ASCII to EBCDIC

ibm from ASCII to alternate EBCDIC

block pad newline-terminated records with spaces to cbs-size

replace trailing spaces in cbs-size records with newline

lcase change upper case to lower case

do not create the output file

excl fail if the output file already exists

do not truncate the output file

ucase change lower case to upper case

swab swap every pair of input bytes

continue after read errors

sync pad every input block with NULs to ibs-size; when used

with block or unblock, pad with spaces rather than NULs

fdatasync physically write output file data before finishing fsync likewise, but also write metadata

Each FLAG symbol may be:

append append mode (makes sense only for output)

direct use direct I/O for data

dsync use synchronized I/O for data

sync likewise, but also for metadata

use non-blocking I/O

do not follow symlinks

noctty do not assign controlling terminal from file

Sending a USR1 signal to a running âddâ process makes it print I/O statistics to standard error and then resume copying.

$ dd if=/dev/zero of=/dev/null& pid=$!
$ kill -USR1 $pid; sleep 1; kill $pid

18335302+0 records in 18335302+0 records out 9387674624 bytes (9.4 GB) copied, 34.6279 seconds, 271 MB/s

Options are:

–help display this help and exit
output version information and exit

Written by Paul Rubin, David MacKenzie, and Stuart Kemp.

Report bugs to .

Copyright © 2006 Free Software Foundation, Inc.
This is free software. You may redistribute copies of it under the terms of the GNU General Public License
. There is NO WARRANTY, to the extent permitted by law.

The full documentation for dd is maintained as a Texinfo manual. If the info and dd programs are properly installed at your site, the

info dd

should give you access to the complete manual.

dd (coreutils) 5.97 November 2006 DD(1)

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