dd is an utility which is primarily used for low-level copying of data from storage devices.

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Check integrity of a dd backup

I just made a backup of an entire hard drive (50GB) over ssh via: dd if=/dev/hda | buffer -s 64k -S 10m | ssh myuser@myhost "cat > ~/image.img" What's now the best way to check the integrity of ...
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1answer
2k views

dd: writing '/dev/null': No space left on device

I am reading a 550MB file into /dev/null and I am getting dd: writing '/dev/null': No space left on device I was surprised. I thought /dev/null is a black hole where you can send as much as you ...
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2answers
596 views

Why did dd create a different uuid?

root@debian:/home/tiger# dd if=/dev/sda of=/dev/sdb bs=10240k 11447+1 records in 11447+1 records out 120034123776 bytes (120 GB) copied, 4729.59 s, 25.4 MB/s root@debian:/home/tiger# blkid ...
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3answers
459 views

from a sparse file to a block device over the network

If I have a sparse file representing a block device, then how can I efficiently restore the file over a network? Ideally, I'd use rsync -S host:file /dev/sdb, but rsync won't write to block devices. ...
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1answer
1k views

How do I create a USB image with a partition table?

I want to create an image of some directory tree that is writable directly to an USB drive, just like the images of many linux distributions. For example, with openSUSE you can download an ISO image ...
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3answers
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dd command for windows filesystem

dd is a handy tool for backing up a whole drive or filesystem in some situations. Now I am thinking about what if I use the tool for backing up Windows file-systems / drives (Windows 2003/2008) which ...
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1answer
2k views

Are there alternatives for `dd`?

What other tools should I use to read and write files with truncation, seeking and skipping. dd's command line options seem inconvenient and foreign and I don't like choosing between slow, but precise ...
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2answers
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Create file image container

I would like to create a 100GB file to use as a file-system. The file will be stored on an encrypted volume, so the file/file-system itself does not need to be (further) encrypted. Searching has ...
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2answers
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Sending the output from 'dd' to awk/sed/grep

I'm trying to approximate the computer's write speed using dd: dd if=/dev/urandom of=/dev/null bs=1K count=10000 which gives the following output 10000+0 records in 10000+0 records out 10240000 ...
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3answers
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How to convert dd disk image to Clonezilla?

I have disk image from VirtualBox, it is a raw image, just like dd makes it, now I would like to restore the system to real machine using Clonezilla. However Clonezilla does not recognize the image ...
2
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2answers
438 views

dd copies more data than exists in .img?

I'm trying to dd an .img file over to my micro sd (8 GB). The rom (.img) is 2.66 GB, but in my output of DD (live) it says its transfered 9 GB. I don't get how it's turning a 2 GB image into 9 GB. I'm ...
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1answer
2k views

What's faster, dd 1.5TB or rsync 500GB?

I need to save data from a failing hard drive. Sounds like ddrescue or myrescue (or maybe clonezilla?) will be my best friends here, but I'm just wondering what will likely be faster: using ...
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2answers
6k views

gzip - redirection or piping?

I will be backing up a large (750GB) disk to an external USB disk using dd. Should I be using redirection or piping? Which is more efficient? Or is there a difference? Also, what is the best block ...
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2answers
3k views

How to write a file at various offsets to a filesystem partition with dd command

Requirement I want to write a file at various offsets into the partition Partition /dev/part2 is mounted at /mypart I tried the command below: dd if=/dev/urandom of=/mypart/aaa bs=1024 seek=0 ...
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3answers
216 views

What happened to my ext3 partition

I had an ext3 partition. I ran a dd command like this: dd if=/dev/urandom of=/dev/part2 bs=1024 count=15000 seek="various values" Where various values are basically 0, 15000K, 30000K etc. The ...
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2answers
3k views

How to check progress when cloning a disk using `dd`? [duplicate]

Possible Duplicate: dd: How do I know if it's still working? I'm using dd to clone a disk to an image file, and compress it on the fly: dd if=/dev/sda | gzip > /mnt/image_file How ...
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3answers
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Why does dd from /dev/random give different file sizes?

I am running the following command on an ubuntu system: dd if=/dev/random of=rand bs=1K count=2 However, every time I run it, I end up with a file of a different size. Why is this? How can I ...
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2answers
4k views

Use `dd` to cut file end part

There is probably simple trick to do this, but I can't figure from man page. How do I cut last 1MB from file with undetermined size for example, by using dd?
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1answer
727 views

Adding a populated existing disk device to a QEMU raw image

I have a raw QEMU image (vda.raw), and I would like to resize it and add an existing partition, using data I have in a file that contains a raw ext3 file system populated with data (vdb.raw). The two ...
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2answers
4k views

Why can't I copy my DVD with dd?

I tried dd, dd_rescue and ddrescue, all failed. I thought these tools bypass the filesystem and make a bitwise copy. dd is fooled, it finishes but just produces a small file and states it's finished. ...
3
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1answer
2k views

What is the fastest way to write all sectors on a drive?

The goal in my case is not to securely erase data, but simply to force sector reallocation by the drives firmware. I have a drive that has had a few file corruptions. It seems to be due to getting ...
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5answers
15k views

Is it possible to mount a gzip compressed dd image on the fly?

I like create an image backup for the first time I'm backing up a system. After this first time I use rsync to do incremental backups. My usual image backup is as follows: Mount and zero out the ...
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2answers
430 views

Embedded device: How to do raw reads and write to flash (emmc/movinand) bypassing file system cache

I have an embedded device with a flash memory running linux. I want to do raw read writes on the flash part but I also want to avoid any file system cache. How can I do this? Any pointers?
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4answers
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Comparison of raw block devices

Is there a utility (or some shell magic) that allows me to compare two block devices? Details: I have one large (0.5 TB) RAID device that I've backed up to a slightly larger SATA device using dd. ...
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1answer
263 views

Backed an ipod up with dd, how to retrieve all tracks in one go with gnupod?

I have had gnupod for a while. Still haven't figured out how to use it though. I usually just go for gtkpod. So this question, in case anyone had any doubts after reading everything below, is purely ...
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3answers
378 views

Some basic questions about dd

I'm working on a system of how to back up partitions using dd and have been reading a lot about it. I have a few questions and assumptions that I would like to ask. These may seem a little noob-ish, ...
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3answers
437 views

Duplicating a hard disk

I'd like to simply duplicate a hard disk drive to another hard disk drive of the same size. I know I can simply do: dd if=/dev/sda of=/dev/sdb (or whatever the names of the drives are in /dev). ...
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4answers
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What's the difference between these two dd commands?

What's the difference between two dd commands that have different bs and count values, as long as they multiply to the same? For example: dd if=/dev/random of=aa bs=1G count=2 dd if=/dev/random ...
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3answers
941 views

Is creating a sparse image using dd appropriate for backup/restore from a RAID?

I have two non-networked servers, each with 1.2TB of storage in a RAID5 config on an LSI MegaRaid 9240-8i controller. I have been trying without success to get Symantec Ghost to image one machine to ...
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2answers
747 views

If I dd a CDROM, then I always get the exact copy of the CDROM?

If I: dd if=/dev/cdrom of=cdrom.iso then I will always get the exact same, bit-by-bitly same image that is the same as the original CDROM? Or are there any methods that prevents copying all the ...
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2answers
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Red Hat cannot boot after clone with dd

I used dd to clone a x4100 server with Linux Red Hat. The hardware is identical for old and new servers. Disks are sda, sdb and sdc(sdc1 and sdc2). But newly restored server gives following errors and ...
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2answers
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When is dd suitable for copying data? (or, when are read() and write() partial)

Short version: In what circumstances is dd safe to use for copying data, safe meaning that there is no risk of corruption due to a partial read or write? Long version — preamble: dd is often used to ...
18
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4answers
6k views

Clone whole partition or hard drive to a sparse file

I like to clone a whole partition or a whole hard drive onto a larger external disk but like to create a sparse file. I often use dd for cloning, but it doesn't support sparse files. As a workaround I ...
5
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3answers
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How can I make a bootable usb flashdrive?

Can I just dd an Ubuntu 11.04 mini.iso to an usb flashdrive an boot from it? or what am I missing?
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7answers
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dd vs cat — is dd still relevant these days?

I recently realized we can use cat as much as dd, and it's actually faster than dd I know that dd was useful in dealing with tapes where block size actually mattered in correctness, not just ...
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7answers
1k views

How to write repeated free-form strings to a file, as fast as 'dd'?

dd can write repeating \0 bytes to a file very fast, but it can't write repeating arbitary strings. Is there a bash-shell method to write repeating arbitary strings equally as fast as 'dd' (including ...
47
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8answers
23k views

How do I know if dd is still working?

I've not used dd all that much, but so far it's not failed me yet. Right now, I've had a dd going for over 12 hours - I'm writing an image back to the disk it came from - and I'm getting a little ...
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4answers
9k views

Is there a way to determine the optimal value for the bs parameter to dd?

On occasion I've seen comments online along the lines of "make sure you set 'bs=' because the default value will take too long," and my own extremely-unscientific experiences of, "well that seemed to ...
25
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6answers
15k views

Best way to remove bytes from the start of a file?

Today I had to remove the first 1131 bytes from an 800MB mixed text / binary file, a filtered subversion dump I'm hacking for a new repository. What's the best way to do this? To start with I tried ...
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4answers
5k views

What does dd stand for?

I know very well what the command does, but man dd, info dd tell me: 'Convert and copy a file', as does GNU Coreutils. Google says its an abbreviation of everything between medicine and bad webchat ...
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5answers
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How do I suppress dd output?

I have a bash script that creates some file using dd. The problem is dd throws a great amount of output that is going to mess with the output of my script. Searching around I've found a solution: dd ...
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3answers
890 views

saving data from a failing drive

An external 3½" HDD seems to be in danger of failing — it's making ticking sounds when idle. I've acquired a replacement drive, and want to know the best strategy to get the data off of the dubious ...
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2answers
616 views

“lshw -C disk” returns but prints nothing

I am using an ubuntu live cd to help me recover some data off of a hard drive. I used lshw -C disk to find out which device I need to copy, /dev/sda in this case. I am using ddrescue -n to try and ...
10
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1answer
14k views

How do I mount an `img` created with /bin/dd of a hard drive?

I used dd to backup a 80GB drive dd if=/dev/sdb of=~/sdb.img Now I need to access some files on that drive, but I don't want to copy the ".img" back over the drive. mount ~/sdb.img /mnt/sdb ...