How Do I Make Linux / UNIX Filesystem Backup With dd?

by on November 16, 2005 · 10 comments· LAST UPDATED October 15, 2008

in , ,

dd command is all in one tool to Copy a file, converting and formatting according to the options. Since Linux (and other UNIX versions) understand everything as a file dd works like wonders. Please note dd is not created specifically for a backup purpose but it is real handy tool. Few months back I was new to HP-UX and I was unable to understand the HP-UX tape devices then I used dd to create backup. Later when I got information of tape device name I switched to age old tar and other dump commands

dd command syntax

The syntax of dd is as follows:


dd command examples

So to backup /dev/hda3 under Linux command should be as follows i.e. linux filesystem backup with dd:
# dd if=/dev/hda3 of=/backup/myhostname-15-nov-05-hda3.bak.dd
However if you are running planning to run dd in background and if you wish to kill it or want to sending a SIGUSR1 single to a running dd process then you need to start dd as follows (this is really useful stuff):
# dd if=/dev/hda3 of=/backup/myhostname-15-nov-05-hda3.bak.dd; dpid=$!
Now use kill command as follows:
# kill -USR1 $dpid; sleep 5; kill $dpid

dd command to backup boot loader / MBR

dd can be use to backup your boot loader too (if you install a Windows after Linux it will destroy grub/lilo boot loader):
# dd if=/dev/hdX of=/backup/mbr.bak bs=512 count=1
You can restore MBR with the following dd command:
# dd if=/backup/mbr.bak of=/dev/hdX bs=512 count=1
Note replace hdX with your actual device name. However I prefer to use grub-install.

Please note that dd is also capable of reading tapes that were created on other UNIX or written in a format other than Unix (like Windows 2000 server).

Here is one more practical example for Solaris UNIX:

To copy all but the label from disk to tape i.e. copy data in 512 KiB blocks between a disk and a tape, but do not save or restore:
# (dd bs=4k skip=1 count=0 && dd bs=512k) </dev/rdsk/c0t1d0s2 >/dev/rmt/0
Copy from tape back to disk, but leave the disk label alone (restore):
# (dd bs=4k seek=1 count=0 && dd bs=512k) < /dev/rmt/0 >/dev/rdsk/c0t1d0s2

Backing up entire disk/partition with dd command

Backup /dev/hda to /dev/hdb:
# dd if=/dev/hda of=/dev/hdb conv=noerror,sync

  • /dev/hda: Source disk
  • /dev/hdb: Target disk
  • sync: Use synchronized I/O for data and metadata
  • noerror: Continue copy operation after read errors

Above command will only work if the both disks are the same size and C/H/S geometry. I strongly suggest using partition level backup. dd is an easy to use (real life saver) command. Read the man page of dd for more information.
$ man dd

TwitterFacebookGoogle+PDF versionFound an error/typo on this page? Help us!

{ 10 comments… read them below or add one }

1 Jann January 28, 2009 at 7:08 pm

I know that you can later on mount partition-level dd dumps. Can you also somehow mount the dump of an entire disk?


2 A person June 25, 2009 at 7:34 pm

RE: Jann…

dunno, give it a try. In unixland, you’d do something like:
mkdir /mnt/mountpoint
mount -t ext3 /somepath/ /mnt/mountpoint


3 Eric J December 16, 2010 at 11:19 am

I never knew about this tool. I was only recently exposed to it while reading how one man managed to boot ubuntu on the CR-48. He dd’ed the ubuntu rootfs to the CR-48 over ssh. SO. COOL.


4 Dave May 19, 2011 at 4:59 pm

I would like to use dd to make a backup of my USB flash drive to my HDD, I’m using a Live CD, both are unmounted.
I tried:
dd if=/dev/usbflashdrive of=/dev/sda1>usbdiskdate.img
This destroyed the ext3 partition.

Any suggestions for improvement?


5 robert June 17, 2011 at 8:04 am


Youre an idiot


6 CesarIII July 20, 2011 at 5:00 am

Hi there,

If you are trying tu backup an USB you can try “dd” + “gzip” so you can compress your backed-up-data. You can improve compression ratio, and even more, If you create a file filled with “0” an then delete it, you’ll obtain a smallest file:

To create a file with “0” so we erase the free area:

dd if=/dev/zero of=DELETE.ME

Once created, delete it.
Once deleted, backup:

dd if=/dev/usbflashdrive | gzip –best > backup.img.gz

You can improve reading/writing by adding “bs” or “obs” on dd… check “man dd”

dd obs=100MB if=/dev/usbflashdrive | gzip –best > backup.img.gz

Make tests… eh!… to restore just do a:

gunzip -c backup.img.gz | dd bs=100MB of=/dev/usbflashdrive



7 Oran November 4, 2011 at 6:19 pm

Thank you for the tutorial. I want to buy an identically sized drive for performing a dd backup, but am concerned about the ability to accomplish this. The drive that I currently have lists the capacity as 251.0 gb (using fdisk). Hard drives that I find advertised only list 250.0 gb. If I get a 250.0 gb hard drive, then the backup could potentially be corrupted due to losing 1.0 gb of space, right? How is this handled? Is there a way to find 251.0 gb hard drives?



8 JIEM February 20, 2012 at 10:03 am

I want to clone a 500GB hard drive (sda) to new hard drive (sdb)
is it possible if using command, dd if=/dev/hda of=/dev/hdb conv=noerror,sync


9 Eric J February 20, 2012 at 1:18 pm

I believe you can. It wouldn’t hurt anything if you did, but the new drive would need to be at least or larger than the old one.


10 CesarIII February 20, 2012 at 4:27 pm

It is possible, if both hard drives are the same manufacturer, model.
If not, you may have a partition table with wrong disk description.
Try something like:

dd bs=100MB if=/dev/hda of=/dev/hdb

to make it in less time.



Leave a Comment

Tagged as: , , , , , , , , , , , , , , , , ,

Previous post:

Next post: