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

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18 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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29 views

Daily backup, online availability and CLI restores. Is tar or dd still the leader? [closed]

At first this may sound like a repeated question, so let me first give my requirements and my analysis of similar posts and why they do not address my concerns. I am looking for a simple Linux-based ...
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1answer
22 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
48 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 ...
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54 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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2answers
278 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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1answer
57 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
79 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
357 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
157 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
41 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
142 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 ...
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1answer
27 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
56 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
78 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 ...
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0answers
862 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 ...
6
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3answers
190 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
89 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 ...
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1answer
68 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 ...
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1answer
70 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 ...
4
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1answer
517 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
60 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
332 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 ...
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1answer
398 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
1k 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 ...
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1answer
162 views

dd output file larger than input file when executed with conv=noerror,sync

I am trying to backup an LVM on one of my servers with the following command: dd bs=4M conv=noerror,sync if=/dev/vg_volgroup/LvmName | ssh myuer@myip "dd of=/home/myuser/LvmName bs=4M ...
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1answer
261 views

dd unable to write to tape drive

I'm trying to dump our online backups to tape; for obvious reasons I want to encrypt the data on the tapes, so to write to the tape I need to tar everything up, pipe that to openssl to encrypt it, ...
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90 views

How to restore a dd image to an EBS volume

I have a local dd image myimage.bin, which I want to use to create an AWS EBS volume. The only way I can figure out how to do this is to, 1) Launch an AWS instance 2) Create and attach an EBS ...
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1answer
168 views

Does 'lvremove' destroy data?

I assign a LV for each vm guest. When deleting a vm, I remove the corresponding lv running 'lvremove'. But is it necessary to destroy the data before running 'lvremove'? Does lvremove do the work of ...
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5answers
447 views

Does filling up disk with dd removes files securely?

I want to remove my files securely without worrying about anyone restoring them, I know I can use shred but it takes too long even with -n 1 so I thought maybe if I remove files and write on the disk ...
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2answers
101 views

DD over SSH from Server to Server

Is it possible to DD one server to another? Maybe through SSH? I've looked around and I have seen examples of DD using SSH from local to server and vice versa, but is it possible to do it from server ...
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2answers
680 views

Why does dd show slow disk speed first time?

I'm checking the disk speed of a hdd on CentOS 6 using dd command. The setup is a DRBD setup - with this server being primary. To ensure that I get correct values, I execute the dd command 3 times ...
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1answer
80 views

rsync, dd and then add to RAID 1, could cause database corrupted?

Firstly I have a HDD which has been setup as RAID, type Volume, not RAID 0 or RAID 1 ... and I wanna add one more HDD to setup a RAID 1 array. These bellow steps are what I've done. Detach from ...
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3answers
158 views

LVM: Using an image of a PV?

I have a logical volume spanning several drives. One of those drives (3TB, the largest of the bunch) is dying, and I am currently making an image of it (via ddrescue). I'm not yet sure on how to use ...
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1answer
64 views

Use dd or redirection to write to tape?

My Googling for writing to tapes with encryption have turned up various results. Most along the lines of piping tar to openssl similar to: tar cf - /home | openssl des3 -salt -k "Your-Password-Here" ...
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1answer
124 views

Correct way to copy vm disk

I have a VM’s disk to copy from one host to another for live migration. I can think of two ways to copy the VM’s disk. Do a snapshot of the Logical Volume in the original host, create a Logical ...
4
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1answer
647 views

Using dd on disks with different sector sizes

I would like to move a partition to a new drive. The old drive has a sector size of 512 bytes while the new one has a sector size of 4096 bytes. I tried doing a dd of the full disk, but that failed ...
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1answer
607 views

Benchmarking GlusterFS & NFS on AWS using iozone and dd gives different results

I have tried benchmarking GlusterFS vs NFS on Amazon Web Services (AWS) using a m1.medium sized EC2 instance. We use the AWS EBS as the block store, with a XFS file system. Running Ubuntu 12.04 ...
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1answer
239 views

How to move partitions from 2 LVM volumes into one LVM on other disk?

i had 2 partitions with following layout Disk /dev/xvda: 376.4 GB, 376354897920 bytes 255 heads, 63 sectors/track, 45755 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Sector size ...
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1answer
402 views

DD broke my whole partition - boot failed: not a bootable disk . Any way to recover it?

Im kind of freaking out here, if anyone can help me please help me... This happened to a Windows 2012 KVM virtual machine. I had a very important database running in it, if I could only recover that ...
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817 views

Differences between hdparm --read-sector and dd with “Current Pending Sectors”

This was originally an "answer" to How to use hdparm to fix a pending sector? I'd been getting SMART notifications for the same "Current Pending Sector" for days. The dd solutions around weren't ...
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2answers
131 views

Cancel /dev/zero before it finishes?

To clear a large hard drive I was using dd if=/dev/zero of=/dev/sda. Only later I realized from reading more sources that the default block size is 512, and if I want the process to go quicker I ...
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1answer
156 views

Why is my synchronized I/O so bad compared to direct?

I have two 3TB disks in a software RAID 1 setup and the host OS is 64bit Debian wheezy. Issuing: dd if=/dev/zero of=test bs=64k count=3k oflag=direct && rm test Yields: 201326592 bytes ...
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1answer
273 views

1. XFS: how to find path / directory of inodes 2. XFS in a file -o loop and ddrescue?

how to find the full original file/directory path of some damaged XFS inodes? and how to list the last modified few 10000 inodes (=edited or moved files/directories) rapidly among millions of ...
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92 views

xfs.image I/O error but harddrive is fine?

Please help to determine, how to may fix this XFS filesystem and whats actually wrong? Thanks! An XFS image runs productive mounted -o loop on debian. a million of files are read every day, only ...
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1answer
220 views

Server crash when creating a swapfile on a running machine (CentOS Linux)

I created a swap file with root on a running server, using swapfile creation guides which I found on the net (http://blog.serverbuddies.com/adding-additional-swap-space-to-your-linux-server/m Create ...
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2answers
3k views

Why is Clonezilla faster than dd?

On my SSD imaging (Source and Destination are 2 SSDs) I get 12GBpm using CloneZilla while with dd I get only 5GBpm. What makes Clonezilla so much faster than dd?
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3answers
61 views

Using dd for backup with a single disk

I have a RHEL5 Amazon cloud instance that I need to image to another instance in order to setup a test environment for some upcoming patching I'm doing. The server to be imaged is a production server. ...
6
votes
1answer
408 views

Experiences with using `dd` to copy multi-partition, multi-FS device

I have a disc with several partitions on, each of which has a different kind of file system (ext3, ext4, and, let's say, NTFS). I want to know if I can copy the whole disc to a new one (which is of ...
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1answer
96 views

how to boot from a backup disk created by dd

I use dd command to backup a disk. #dd if=/dev/sda of=/dev/sdb but when I boot from the backup disk, I got a error message check filesystem failed! I do not know how to settle this problem. I ...