This command is used to do low level copying of data.

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How to clone a partition of LUKS disk?

I have cloned a LUKS drive whose volume is 16012804096 bytes ( on a kingstone sd card). I want to recover it to another SD card ( another sandisk SD card ). But the volume of sandisk card is ...
2
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1answer
38 views

how to intentionally damage linux MBR (RHEL 7) on disk for test purpose?

I am running tests for MBR recovery on Red Hat Linux 7. I tried to intentionally erase the MBR with: dd if=/dev/random of=/dev/sda bs=1 count=512 I can see with fdisk -l /dev/sda that the ...
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12 views

DD + LVM Snapshot + Space shortage

Here is the scenario : I have a production system that can't be shutdown for very long, it has the following root filesystem LVM: [root@an2 ~]# df -h Filesystem Size Used ...
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1answer
38 views

How to use dd to dump an image to unallocated space

I have a bin file (chromiumos_image.bin) which contains some (around 12) partitions, which I need to dump into the unallocated space between 2 other partitions. The partition table is this: My ...
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2answers
42 views

How to mount the dd image of a swap file

I have several dd images from a single drive. One of them is the swap. I mounted all of the images in Ubuntu just fine except for the image of the swap. This is how the dd images break down: hda8 is /,...
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36 views

ZFS mirror migrated to other system with dd -> zpool import fails

I'm pretty new to ZFS and this might be an easy problem (but I don't find any discussions about how to do this): I've messed up a FreeBSD installation on a Root-on-ZFS mirrored ZFS Pool on a ...
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1answer
67 views

Installing CentOS on HP Server, SSDs connected to a RAID controller

I am trying to install centOS 6.0 in this HP Server, I contacted with the support and they said me that it supports that OS. I have no problem installing it on a SSD that is connected directly to ...
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1answer
48 views

dd: zero-out all the remaining unused space of a drive

In the second answer of this question about disk cloning with 'dd', I read this command: dd if=/dev/zero of=/mnt/hdb/zero It is supposed to write '0' in the unused space of drive 'hdb', however I ...
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1answer
41 views

Using DD to produce an Image results in empty image [closed]

I am trying to take an image of my Android phone. Specifically I have tried to image the system and boot partitions. The imaging process appears to work correctly when using dd. However, when I ...
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26 views

Shrinking an img file that contains linux partitions

I've got an img file (4,02GB) containing a Linux OS. My goal is to shrink this img filed down to < 4GB. The img contains a linux partition that only holds about 2,5GB of data. I need to be able to ...
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1answer
57 views

Segmentation fault on dd command

I ran this command on Ubuntu to resize the /tmp and after that there is segmentation fault coming. dd if=/dev/zero of=/dev/xvda1 bs=1024M count=2 Its our live server. Is there any way to get it ...
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227 views

Acceptable I/O speeds for 6 x 250GB SSDs in RAID 10

I'm running CentOS 7 (XFS filesystem) on a dell server with a PERC H700 raid controller. Inside this server I have 6 x Samsung 850 Evo 250GB SSDs (yes they are consumer drives however, this is a home ...
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1answer
29 views

Backup old disk to external disk (new)

One of the 2 x 500GB drives on server is crashed can read but not write the data, which both are on Hardware RAID 0. So I connected an external 1TB new drive to backup the data and replace those 2 x ...
7
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1answer
177 views

File is too big for /dev/null

While testing a problem LUN for read errors, I encountered the following problem: find /mnt/problem_lun/ -type f -print -exec dd if={} of=/dev/null bs=8k \; ... /mnt/problem_lun/a_file dd: writing `/...
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3answers
144 views

Truncate empy space from a raw dd image

I have a raw disk image I took using dd of a Ubuntu instance. The total disk size is 300 GB, but only 5.5 GB used. Is there a way to resize the raw dd image down to 20 GB, keeping all of the 5.5 GB ...
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2answers
453 views

How to execute bash script through pxe boot [closed]

Can any one tell me how to execute bash scripts via pxe boot. What I am trying to do is when Raw Server boots up I want to deploy cloned image over hard disk via PXE boot. I am aware that there are ...
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1answer
144 views

Create random file with openssl [closed]

So I read this questionUrandom Alternative, but I am unable to make a comment there (without 50 rep) - therefore I open a separate question: If I use this command instead of dd and urandom, how do I ...
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2answers
103 views

Reduce xen image disk usage

Two cases: 1.If making hdd image using dd and copy it trough nfs to another server: mount -o ro,remount / dd if=/dev/sda bs=64K | gzip -c > /share/test.img.gz then after gunzip I get 20Gb (for ...
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1answer
70 views

dd vs. dd pipelined: which is better? [closed]

Here I read, in the comments, that a guy got more performance when used dd in pipeline for a copy. Like for example: dd if=in | dd of=out instead of dd if=in of=out Is it really faster? Why? ...
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1answer
60 views

Make a dd image restorable to a smaller drive

Suppose I have a 32 GB USB flash drive (UFD) and an 8 GB UFD. I have a 5 GB partition at the start of the bigger UFD, and the rest is unallocated. The problem is to copy the partition and boot sector ...
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1answer
159 views

Copy LVM volume group spanning two physical volumes on two disks

[update] i have copied the two primary partitions using gparted. now i am stuck trying to copy a single volume because it is made of two physical volumes each on separate disk...ideas? /sda5, /sdb1 = ...
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1answer
51 views

The best way to copy OS on RAID10 and lvm partition

I need to backup/clone the entire operating system. The problem is it's 2TB of data on lvm partition and RAID10 (i do not know is it dedicated controller or fake RAID in BIOS. Probably the second ...
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313 views

Creating IPsec tunnel Ubuntu 15.04 ip sec tools

I'm trying to setup a VPN/Tunnel between three(3) Ubuntu 15.04 servers. I've googled and it seems that I can use IPsec tools for this. I've only found the following tutorial:https://help.ubuntu.com/...
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71 views

Deleted MBR on virtual machine on purpose, but entries are preserved

I'm playing with Master boot record. I decided to delete and restore it on my vmware machine. With Ubuntu LiveCD I'm trying to erase partition entries and signature with command: dd if=/dev/zero of=/...
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3answers
3k views

Cloning LVM partitions

I need to clone a CentOS installation from a 1TB disk partitioned with LVM, to several identical machines. The disk is mostly empty since only the operating system and some software are installed and ...
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4answers
2k views

Wipe is very slow. Too little entropy?

I have to hand off a Laptop including its hard disc. Since it was not encrypted I wanted to wipe it at least quickly. I know this is not optimal on SSD, but I thought better than just plain readable. ...
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0answers
429 views

Slow IO Performance with PERC H700/710 with current linux distributions

we noticed really bad write performance, on our new Dell R720 with Perc 710. Especially when it come to writing a lot of small files. The funny thing is that this bad performance only occurs on newer ...
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1answer
85 views

ddrescue — which files are in error locations?

I had a HDD crash and had to use ddrescue to restore it. It took a month, but it finally finished today. However, there were three errors that it could not read. Is there a way to find out which files ...
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1answer
222 views

Remote bash script execution via ssh causes local script to stop

I have a setup which behaves in a way i cannot get my head around. So I have a local bash script generateTrafficOnHosts.sh which reads IP addresses from a file. It then calls a bash script getTraffic....
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1k views

Create a VHD file from a Linux disk

I have a disk containing CentOS 5.8 that was removed from a dead box. I would like to make a VHD file from this disk so I can run a virtual machine (instead of a new physical machine). The Virtual ...
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532 views

How to mount dd image of digital ocean?

I have created a dd image of /dev/vda using the following command: ssh root@1.2.3.4 "dd if=/dev/vda" | dd of=/home/backup/vda.img and I can't mount it on my local Ubuntu server where I ...
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318 views

fio on virtual disk created with dd to stress disk

I am trying to create a script for my coworkers to use in the field that will stress the internal disks to a Linux server. I plan to put some logic in for finding the /dev/sd's available and such. But ...
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1answer
293 views

How can I resume a dd operation after a “error writing in file” status?

This command produced the error mentioned above after 9 h (preparing a 2 TB hdd for encryption): time openssl enc -aes-256-ctr -pass pass:"$(dd if=/dev/urandom \ bs=128 count=1 2>/dev/null | ...
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2answers
9k views

Does the “bs” option in “dd” really improve the speed?

Every now and then, I'm told that to increase the speed of a "dd" I should carefully choose a proper "block size". Even here, on ServerFault, someone else wrote that "...the optimum block size is ...
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2answers
735 views

Linux dd: Is there a way to redirect its output for monitoring?

Sometime the servers in my workplace experience some weird behavior, it happens in random physical racks around different DC's around the world. It seems like there's a networking bandwidth issues ...
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1answer
115 views

Simple scheme for backup virtual machine, which drawback of simple DD?

We've been struggling to create the consistent scheme for backup of KVM virtual machines under Proxmox control and Ceph as storage, but still quite often during the vzdump with a snapshot the virtual ...
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2answers
803 views

How to clone a RAID5 system

I clone single disk systems by booting the master system to a CD and running… dd if=/dev/sda | gzip - | ssh user@hostname dd of=image.gz Then I boot the target system with the CD and run… ssh user@...
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1answer
36 views

Disk image growing in size [closed]

I am trying to set up Rasberry pi for jobs that don't deserve bigger machine. I downloaded a Pidora disk image (.img) zipped it is roughly 512MB. After unzipping it is 2.2GB ( no problem here). ...
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2answers
98 views

HHD cloning with dd on running server

Is it possible to clone HDD with dd command on linux while server is up and running. Server running, Apache, MySql, NGINX. I ask this coz won't have downtime.
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1answer
131 views

When copying VM filesystem over netcat, dd copies double the disk size

I'm attempting to copy the disk of a working headless virtualbox VM (VM1) on one server to a new VM (VM2) on a vCloud server. I don't have access to the host of VM2. The OS is Windows Server 2003 (32-...
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0answers
2k views

Cloning a bitlocker encrypted disk

Our company's had its laptops for just over 2 years now and they have all become slow and many of them have had their harddisks dying randomly lately. I noticed that many of my colleagues use a tilted ...
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3answers
342 views

Best way to clone a Linux system

I've just finished setting up a Debian system running on an embedded device. It has custom partitioning, numerous config file changes, web content, and a couple of applications compiled from source. ...
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1answer
105 views

Fixing partition table after writing 0s to beginning

I have a sw raid10 setup like: /dev/sdX > partition /dev/sdX1 > raid md0 > lvm > fs. I'm an idiot, and wrote 4gb of 0s to /dev/md0 with dd dd if=/dev/zero of=/dev/md0 bs=4k count=1000000 conv=...
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1answer
131 views

dd or cat - overload when read /dev/zero

I need reclamation thin disk, so Im trying fill zero on vhdd. But when I run it, so server is overload with 20k IOPS and full satured SAN network. Can you help me how I can slow b/w for this? E.g 10MB/...
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78 views

Anyone tried dd'ing Raidmembers?

I want replace all disks in a 10 disk raid6 (linux software raid). I could do this by pulling a disk, let the array rebuild, rinse, repeat. But this would take a very long time, and cause 10 ...
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1answer
1k views

Linux page cache slows down IO on dual cpu server with 64GB ram

I have a massive problem with the linux page cache which slows down the IO. For instance if I copy a lvm partition with dd, linux cache the data in the buffers or caches (free –m). That is not the ...
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1answer
79 views

handle multiple calls of rsync, dd and snapshot

The server runs the following operations often. It takes a snapshot of a logical volume, then backup up the content to the remote backup server. It is possible that multiple backups and transfer ...
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1answer
515 views

On a system with 64GB mem the Linux Buffer run full while copying with dd to dev null and io stops till manual drop_caches

I am running a server with linux software raid 10. It is a dual CPU system with 64GB Ram. 2x16GB dimms related to each of the CPUs. I want to use dd to backup kvm virtual machines and run into a ...
3
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1answer
805 views

Large write with dd fail on RAID-5

I have a server with a RAID controller which connects to a JBOD over SAS. JBOD is populated with 16 SAS-HDDs of 3TB (8 of one make and 8 of other, same rpm). I have configured 3 logical drives with ...
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1answer
3k views

dd command piped over gzip and ssh faster and faster as dd progresses

I am running the following command to copy a LVM from one host to another: dd if=/dev/vg_1/lv1 conv=noerror,sync bs=4M | gzip | ssh user@ip 'gzip -d | dd of=/dev/vg_2/lv1 bs=4M' To begin with I was ...