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Disk cloning

From ArchWiki

Disk cloning is the process of making an image of a partition or an entire hard drive. This can be useful both for

copying the drive to other computers and for backup/recovery purposes. There is also a dedicated page FileRecovery.

Contents

1 Using dd

1.1 Cloning a partition

1.2 Cloning an entire hard disk

1.3 Backing up the MBR

1.4 Create disk image

1.5 Restore system

1.6 Examples with compression

1.6.1 7zip

1.6.2 Zip

1.6.3 Rar

1.6.4 Bzip2

2 Using cp

3 Disk cloning software

3.1 Disk cloning in Arch

3.2 Disk cloning outside of Arch

4 External Links

Using dd

The dd command is a simple, yet versatile and powerful tool. It can be used to copy from source to destination,

block-by-block, regardless of their filesystem types or operating systems. A convenient method is to use dd from

live environment, as in a livecd.

Warning: As with any command of this type, you should be very cautious when using it; it can destroy data.

Remember the order of input file (if=) and output file (of=) and do not reverse them! Always ensure that the

destination drive or partition (of=) is of equal or greater size than the source (if=).

Cloning a partition

From physical disk /dev/sda, partition 1, to physical disk /dev/sdb, partition 1.

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dd if=/dev/sda1 of=/dev/sdb1 bs=4096 conv=notrunc,noerror,sync

If output file of (sdb1 in the example) does not exist, dd will start at the beginning of the disk and create it.

Cloning an entire hard disk

From physical disk /dev/sda to physical disk /dev/sdb

dd if=/dev/sda of=/dev/sdb bs=4096 conv=notrunc,noerror,sync

This will clone the entire drive, including MBR (and therefore bootloader), all partitions, UUIDs, and data.

notrunc or 'do not truncate' maintains data integrity by instructing dd not to truncate any data.

noerror instructs dd to continue operation, ignoring all read errors. Default behavior for dd is to halt at any

error.

sync writes zeroes for read errors, so data offsets stay in sync.

bs=4096 sets the block size to 4k, an optimal size for hard disk read/write efficiency and therefore, cloningspeed.

Note: To regain unique UUIDs, use "tune2fs /dev/sdbX -U random" on every partitions. (works for ext* file

systems only)

Note: Partition table changes from dd are not be registered by the kernel. To notify of changes without

rebooting, use a utility like partprobe (part of GNU parted).

Backing up the MBR

The MBR is stored in the the first 512 bytes of the disk. It consist of 3 parts:

1. The first 446 bytes contain the boot loader.

2. The next 64 bytes contain the partition table (4 entries of 16 bytes each, one entry for each primary

partition).

3. The last 2 bytes contain an identifier

To save the MBR into the file "mbr.img":

# dd if=/dev/hda of=/mnt/sda1/mbr.img bs=512 count=1

To restore (be careful : this could destroy your existing partition table and with it access to all data on the disk):

# dd if=/mnt/sda1/mbr.img of=/dev/hda

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If you only want to restore the boot loader, but not the primary partition table entries, just restore the first 446 byte

of the MBR:

# dd if=/mnt/sda1/mbr.img of=/dev/hda bs=446 count=1

To restore only the partition table, one must use

# dd if=/mnt/sda1/mbr.img of=/dev/hda bs=1 skip=446 count=64

You can also get the MBR from a full dd disk image.

#dd if=/path/to/disk.img of=/mnt/sda1/mbr.img bs=512 count=1

Create disk image

1. Boot from a liveCD or liveUSB.

2. Make sure no partitions are mounted from the source hard drive.

3. Mount the external HD

4. Backup the drive.

# dd if=/dev/hda conv=sync,noerror bs=64K | gzip -c > /mnt/sda1/hda.img.gz

5. Save extra information about the drive geometry necessary in order to interpret the partition table stored within

the image. The most important of which is the cylinder size.

# fdisk -l /dev/hda > /mnt/sda1/hda_fdisk.info

NOTE: You may wish to use a block size (bs=) that is equal to the amount of cache on the HD you are backing

up. For example, bs=8192K works for an 8MB cache. The 64K mentioned in this article is better than the default

bs=512 bytes, but it will run faster with a larger bs=.

Restore system

To restore your system:

# gunzip -c /mnt/sda1/hda.img.gz | dd of=/dev/hda

Examples with compression

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When you need to create the hard drive or a single partition compressed backup image file you must use

compression tools which can do backup from a stdout and thedd command. Those compressed files cannot be

mounted by the mount command but are useful to know how to create and restore them.

7zip

Install the p7zip (https://www.archlinux.org/packages/?name=p7zip) package from the official

repositories. This backup example will split the dd command output in the files by up to the 100 megabyte each:

dd if=/dev/sdXY | 7z a -v100m -t7z -si image-file.7z

Restore with 7zip:

7z x -so image-file.7z | dd of=/dev/sdXY

Note: 7zip can split only the 7z compression type files

Zip

Install the zip (https://www.archlinux.org/packages/?name=zip) package from the official repositorie

which contains zipsplit among other utilities for the management of zip archives. It will create a file with "-" name

inside the image-file.zip file which will contain data from the dd command output. To make a raw output of the file

you can use the -cp option withunzip in stdout for the dd command. Backup:

dd if=/dev/sdXY | zip --compression-method bzip2 image-file.zip -

Restore:

unzip -cp image-file.zip | dd of=/dev/sdXY

The zip tool cannot split files on the fly but you can use the zipsplit utility on an already created file.

See also man zip for more information.

Rar

Install the rar (https://aur.archlinux.org/packages/rar/) package from the AUR.

Warning: The rar examples were made based on the manuals, please confirm!

This should do a backup and split the creating file on the fly in by up to 150 megabyte files each.

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dd if=/dev/sdXY | rar a -v150m -siimage-file.rar

This should restore

unrar x -p image-file.rar | dd of=/dev/sdXY

or you can use the rar instead of theunrar (https://www.archlinux.org/packages/?name=unrar) utiliThe unrar utility is available in the official repositories and can be installed with pacman -S unrar .

Bzip2

Creation by using the dd is more safe and use to be error free:

dd if=/dev/sdXY | bzip2 -f5 > compressedfile.bzip2

937016+0 records in937016+0 records out479752192 bytes (480 MB) copied, 94.7002 s, 5.1 MB/s

And a safe way of restoring with combination of the dd:

$ bunzip2 -dc compressedfile.bzip2 | dd of=/dev/sdXY

or

$ bzcat compressedfile.bzip2 | dd of=/dev/sdXY

Warning: Never ever use the bzip2 -kdc imgage.bzip2 > /dev/sdXY and

bzip2 -kc /dev/sdXY > imgage.bzip2 methods for serious backup of partitions and disks. The errors

might be due the end of the device or partition and the restore process gives also errors due the truncated end.

Using cp

The cp program can be used to clone a disk, one partition at a time. An advantage to using cp is that the filesystem

type of the destination partition(s) may be the same or different than the source. For safety, perform the process

from a live environment.

Note: This method should not be considered in the same category as disk cloning on the level at which dd

operates. Also, it has been reported that even with the -a flag, some extended attributes may not be copied. For

better results, rsync or tar should be used.

The basic procedure from a live environment will be:

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Create the new destination partition(s) using fdisk, cfdisk or other tools available in the live environment.

Create a filesystem on each of the newly created partitions. Example:

mkfs -t ext3 /dev/sdb1

Mount the source and destination partitions. Example:

mount -t ext3 /dev/sda1 /mnt/sourcemount -t ext3 /dev/sdb1 /mnt/destination

Copy the files from the source partition to the destination

cp -a /mnt/source/* /mnt/destination

-a: preserve all attributes , never follow symbolic links and copy recursively

Change the mount points of the newly cloned partitions in /etc/fstab accordinglyFinally, install the GRUB bootloader if necessary. (See GRUB)

Disk cloning software

Disk cloning in Arch

Partclone provides utilities to save and restore used blocks on a partition and supports ext2, ext3, ext4, hfs+

reiserfs, reiser4, btrfs, vmfs3, vmfs5, xfs, jfs, ufs, ntfs, fat(12/16/32) and exfat. Optionally, a ncurses interfa

can be used. Partclone is available in the community repository.

Partimage (http://www.partimage.org/), an ncurses program, is available in the community repos. Partimage

does not currently support ext4 or btrfs filesystems. NTFS is experimental.

Disk cloning outside of Arch

If you wish to backup or propagate your Arch install root, you are probably better off booting into something else

and clone the partition from there. Some suggestions:

PartedMagic (http://partedmagic.com/doku.php?id=start) has a very nice live cd/usb with PartImage and

other recovery tools.

Mindi (http://www.mondorescue.org/) is a linux distribution specifically for disk clone backup. It comes with

its own cloning program, Mondo Rescue.

Acronis True Image is a commercial disk cloner for Windows. It allows you to create a live (from within

Windows), so you do not need a working Windows install on the actual machine to use it. After regitratinon

of the Acronis software on their website, you will be able to download a Linux based Live cd and/or plugin

for BartPE for creation of the Windows based live cd.

FSArchiver (http://www.fsarchiver.org/Main_Page) allows you to save the contents of a file system to a

compressed archive file. Can be found on the System Rescue CD (http://www.sysresccd.org/Main_Page).

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Clonezilla (http://clonezilla.org/) is an enhanced partition imager which can also restore entire disks as well a

partitions.

Redo Backup and Recovery (http://redobackup.org/) is a Live CD featuring a graphical front-end to

partclone.

External Links

Wikipedia:List of disk cloning softwareArch Linux forum thread (https://bbs.archlinux.org/viewtopic.php?id=4329)

Retrieved from "https://wiki.archlinux.org/index.php?title=Disk_cloning&oldid=330364"

Categories: Data compression and archiving System recovery

This page was last modified on 15 August 2014, at 12:08.

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