dd is a traditional utility for binary data copies

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Wipe files from an external hard drive but not empty space

I'm using the following command to wipe an external drive. sudo shred -v -z -n 1 /dev/sdb Is it possible to wipe an external drive of the files and not empty space? So it would overwrite where ...
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1answer
31 views

GDiskDump or DD to show partition names? [duplicate]

I have partition names like Data-HD, Yhteinen and W10. I do have lots of other partitions, but I want a little more assurance I am copying a right partition to a correct destination. I am quite ...
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2answers
95 views

8GB USB disk listed at only 512B or 10MB?

I made an Arch Linux ISO USB drive, and I'm trying to restore it using the directions from the Arch Linux wiki. After running: $ sudo dd count=1 bs=512 if=/dev/zero of=/dev/sde && sync ...
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1answer
29 views

Taking and restoring an image of partition with dd

I created a new partition on my server /dev/sda4 with a filesystem based on ext3. I mounted the new partition /dev/sda4 on /mnt/sda4/ and created an image with dd of the partition /dev/sda3. sda3 is ...
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2answers
431 views

How large is the img that dd creates?

This is the first time I use the dd command. I execute: dd if=/dev/sdb2 of=/mnt/sdc1/Hdd1.img bs=512 conv=noerror,sync Where the sdb is the destroyed hdd (size: 500 GB). I copying the partition ...
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0answers
14 views

ARM inforce IFC6540 not booting?

I created an image of the OS on the 64GB SD card by using dd. I did something like sudo dd if=./iforgot of=/media/usb/os/os.image I can't remember the exact stuff I wrote, but I do have the os.image ...
2
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1answer
38 views

Is there a way for a dd of a 80 GB hard drive to be minimal in size?

For backup reasons I need to use dd to copy a whole hard drive (including MBR, partitions,...). The hard drive is 80 GB in size where only 1.8 GB are used. The command I'm using is the following: dd ...
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22 views

Is it feasible to fill a ntfs partition/device pre install with zeroess?

In my question about copying with dd one of the commentors pointed out the method of filling the unused space with 0s. Is there a way for a dd of a 80 GB hard drive to be minimal in size? Now after ...
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31 views

dd process real vs. sys time

I have two quad core workstations. One is based on Intel Atom x86_64 architecture (WS1). Another one is based on armv7l architecture (WS2). Both are running 3.10 kernel version. Identical busybox dd ...
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4answers
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Create random data with dd and get “partial read warning”. Is the data after the warning now really random?

I create a 1TB file with random data with dd if=/dev/urandom of=file bs=1M count=1000000. Now I check with kill -SIGUSR1 <PID> the progress and get the following: 691581+0 Datensätze ein ...
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4answers
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Read the middle of a large file

I have a 1 TB file. I would like to read from byte 12345678901 to byte 19876543212 and put that on standard output on a machine with 100 MB RAM. I can easily write a perl script that does this. ...
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4answers
61 views

MBR size is 440 bytes or 512 bytes

I remembered reading one question how would you back up the MBR of a disk. Two of the choices are dd if=/dev/sda of=/dev/sdb bs=512 count=1 dd if=/dev/sda of=/dev/sdb bs=440 count=1 and the ...
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0answers
17 views

Used dd on a pen drive (wrote Arch to it with Rufus) and now it's invisible

I ran dd if=/dev/zero of=/dev/sdc count=2048 on the pen drive. I can see the pen drive in the lsusb output, and dmesg says that it is 8 GB in size, but when I use, say, cfdisk, it says that there is ...
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2answers
36 views

dd count default

What is the count default in dd command if not specified ? dd if=/dev/mem bs=1k skip=768 instead of full form like dd if=/dev/mem bs=1k skip=768 count=50 I did not find an answer with Google.
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13answers
66k 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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5answers
5k views

Fast Way to Randomize HD?

I've read about how to make hard drives secure for encryption, and one of the steps is to write random bits to the drive, in order to make the encrypted data indistinguishable from the rest of the ...
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2answers
70 views

how to deallocate /dev/ram0

I have allocated /dev/ram0: dd if=/dev/zero of=/dev/ram0 bs=1M count=1024 Now I have 1Gb sitting in memory. How do I free up the allocated space ?
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1answer
502 views

What does this dd command do exactly?

I have an embedded device with this SD card: [root@(none) ~]# busybox fdisk -l Disk /dev/mmcblk0: 3965 MB, 3965190144 bytes 4 heads, 16 sectors/track, 121008 cylinders Units = cylinders of 64 * 512 = ...
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1answer
20 views

I/O Failure when overwriting entire disk

I'm trying to write random data over a partition on my local hard disk. I'm booted into a recovery live CD (Clonezilla) and have tried the following: $ dd if=/dev/urandom bs=1024 count=4 | base64 | \ ...
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1answer
43 views

Parallelize openssl as input to dd

I am using @tremby's great idea to fill a disk with random data. This involves piping openssl, which is encrypting a lot of zeros, to dd (bs=4M). I'm maxing out the single core on which this is ...
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1answer
24 views

Transfer content of LVM block device ensuring consistency - LVM snapshot?

I need to create off-site full backups of an LVM block device. Thinking the old dd over SSH method. To ensure I have a consistent backup, should I create an LVM snapshot first? So new changed blocks ...
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7answers
28k 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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2answers
81 views

How can I manipulate a partition table file without fdisk checking the validity of it?

I'm creating an image in memory (/tmp is a tmpfs): $ dd if=/dev/zero of=/tmp/sdcard.img bs=512 count=3147775 It's supposed to hold a partition table and the first 3 partitions of a device $ ...
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1answer
50 views

Using dd command to download mtd block

How to use dd command to download mtd block from embedded Linux-based device? # cat /proc/mtd dev: size erasesize name ... mtd3: 003a0000 00010000 "DRTI2" I need download mtd3 block, so dd ...
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2answers
828 views

Why do these duplicated SD cards have different sha1sums for their content?

I have a bunch of Class 10 UHS-1 SDHC SD cards from different manufacturers. They are all partitioned as follows $ sudo fdisk -l /dev/sdj Disk /dev/sdj: 14.9 GiB, 15931539456 bytes, 31116288 sectors ...
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2answers
51 views

Is `dd` really necessary to clone a disk? [duplicate]

Almost any tutorial will tell you that to clone a disk on the command line (say, to clone /dev/sda to /dev/sdb) you can use: dd if=/dev/sda of=/dev/sdb ...and some block size options... This reads ...
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6answers
4k views

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
84 views

dd, cat & openssl: block size & buffer size

Here it says that when using dd through dm-crypt to overwrite a block device, only the default dd block size should be used because dm-crypt's block size is the same (512 bytes), and increasing dd's ...
2
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1answer
26 views

Compare two files, while overriding second file's size

I am trying to verify a backup that I made using the following command: dd if=/dev/sda of=/dev/sdc2 I backed up the contents of /dev/sda (internal hard drive) to /dev/sdc2 (external backup drive, ...
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1answer
195 views

Can I uncompress a zip file containing a disk image and then save that to an SD card all in one step?

I am under the following restrictions: I have a 1.0 GB .zip file on my computer which contains one file, a disk image of raspbian. When uncompressed, this file is 3.2 GB large and named ...
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0answers
35 views

Restore errors: “bad header/extent: invalid magic - magic 1701”

I'm testing these instructions to restore a backup image to an Intel Edison from a previous .img image. The backup line was: dd if=/dev/mmcblk0 of=sd/ubilinux_image.img I removed a file (to see if ...
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2answers
90 views

Why is dd reading from and writing to the same disk?

I've been using dd in Linux to overwrite an external USB hard drive. When I use the default block size of 512 bytes, with this command: # dd if=/dev/zero of=/dev/sdb throughout the whole ...
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3answers
348 views

Copy content from files X and Y to create file XY but XY content is all lowercase

What's the right command to copy the content from file X and File Y to create a new File XY with all letters being lowercase?
2
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1answer
77 views

Why dd reads from output device?

While dding a CentOS 7 x86_64 DVD image to a USB drive (sdb), I monitored the progress with iostat. It kept alternating between mostly writing to the USB drive: Device: tps kB_read/s ...
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57 views

dd speedup by async reads/writes

I was copying an SSD to an identical one today: dd if=/dev/sda of=/dev/sdb bs=4M They were connected by a SATA cable. While stracing dd I noticed that it was doing the "naive" thing: read 4M from ...
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4answers
397 views

Multiple passes of wiping disk with `dd`

I want to use dd to overwrite a disk multiple times to destroy data beyond recovery. I know I could use dd if=/dev/zero/ of=/dev/sdx/ to do a pass with zeros, or dd if=/dev/null/ of=/dev/sdx/ to ...
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5answers
11k 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 ...
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2answers
7k views

Unpack files and directories from an image created by dd?

I created an image of an NTFS partition using dd. I wonder if I can unload/unpack the files and directories in the image to any partition whose size is larger than the image size, so that I can ...
4
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1answer
114 views

How does cat 'know' the optimum block size to use?

From reading this, it seems that when copying data to a different hard drive, cat automatically uses the optimum block size (or very near it). I wonder how it determines the optimum block size, and ...
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3answers
86 views

Using dd to clone a disk while mounted - risks?

I want to clone a hard disk using dd. Because I want to keep a process on the machine alive continuously, I would like to do this while the filesystem is still mounted. I understand this is not the ...
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1answer
26 views

How to recover a node/content from a tarfile that's been overwritten

Disclaimer: I'm not very good at writing questions, and mine is a very specific scenario. So I'm just going to jump straight into the situation: I was browsing my filesystem, and somehow managed to ...
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1answer
39 views

Pretty print output of “kill -USR1”-ing dd

When dd is done it prints a three line summary about the number of read and written segments, the total size and average writing speed. While it does its work, dd is awfully quiet. Not too long ago ...
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1answer
53 views

USB key does not show up in /dev

We use a USB key system that are contain license files and are provided to unlock proprietary software that we used. The USB drives are small however and get lost easily, so I thought I'd clone them ...
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3answers
365 views

How do I DD over the network to an external HD?

I'm trying to clone a hard drive on my raspberry pi which is on the same network to an external harddrive of the computer I'm currently on. However I'm having issues piping the command correctly. I've ...
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2answers
69 views

Faster way to DD?

I am trying to DD a raw file to an SSD from a spin usb spin drive. I have tried compression (but it obviously has to expand before it can copy). I have watched the details of the arm7 gb ram device... ...
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2answers
321 views

restore dd cloned sd card (No space left on device)

I used this command sudo dd bs=4M if=/dev/sdb1 | gzip > /home/username/image`date +%d%m%y`.gz to clone my 32gb sd card (there was linux installed for odroid U3) now I have tried to restore it on ...
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1answer
114 views

How to fix BTRFS superblock error after resize/shrink (BTRFS: couldn't get super buffer head for bytenr 274877906944)

BTRFS RAID1 array with 2 500 GB hdds, no errors. This is the root filesystem, so there are 3 partitions on each drive: 1 = /boot (ext4), 2 = / (btrfs), 3 (swap) /boot is ext4 because upgrading the ...
5
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4answers
6k 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. ...
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3answers
618 views

What does the two numbers mean respectively in dd's “a+b records” stats?

The first 2 lines in dd stats have the following format: a+b records in c+d records out Why 2 numeric values? What does this plus sign mean? It's usually a+0, but sometimes when I use bigger block ...
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4answers
10k 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 ...