Commands using dd sorted by votes

Commands using dd (167)

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Create a CD/DVD ISO image from disk.

This example is taken from Cygwin running on Win7Ent-64. Device names will vary by platform. Both commands resulted in identical files per the output of md5sum, and ran in the same time down to the second (2m45s), less than 100ms apart. I timed the commands with 'time', which added before 'dd' or 'readom' gives execution times after the command completes. See 'man time' for more info...it can be found on any Unix or Linux newer than 1973. Yeah, that means everywhere. readom is supposed to guarantee good reads, and does support flags for bypassing bad blocks where dd will either fail or hang. readom's verbosity gave more interesting output than dd. On Cygwin, my attempt with 'readom' from the first answer actually ended up reading my hard drive. Both attempts got to 5GB before I killed them, seeing as that is past any CD or standard DVD. dd: 'bs=1M' says "read 1MB into RAM from source, then write that 1MB to output. I also tested 10MB, which shaved the time down to 2m42s. 'if=/dev/scd0' selects Cygwin's representation of the first CD-ROM drive. 'of=./filename.iso' simply means "create filename.iso in the current directory." readom: '-v' says "be a little noisy (verbose)." The man page implies more verbosity with more 'v's, e.g. -vvv. dev='D:' in Cygwin explicitly specifies the D-drive. I tried other entries, like '/dev/scd0' and '2,0', but both read from my hard drive instead of the CD-ROM. I imagine my LUN-foo (2,0) was off for my system, but on Cygwin 'D:' sort of "cut to the chase" and did the job. f='./filename.iso' specifies the output file. speed=2 simply sets the speed at which the CD is read. I also tried 4, which ran the exact same 2m45s. retries=8 simply means try reading a block up to 8 times before giving up. This is useful for damaged media (scratches, glue lines, etc.), allowing you to automatically "get everything that can be copied" so you at least have most of the data. Show Sample Output
This is sample output - yours may be different.
```
sharkins@L7EIS-TEL023 /cygdrive/c/Zip/HP/USB HD 720p Business Webcam
$ time readom -v dev='D:' f='./HP-HD-2200_ViaReadom-Take3.iso' speed=2 retries=8
scsidev: 'D:'
devname: 'D'
scsibus: -1 target: -1 lun: -1
Read  speed:  1764 kB/s (CD  10x, DVD  1x).
Write speed:     0 kB/s (CD   0x, DVD  0x).
Capacity: 59379 Blocks = 118758 kBytes = 115 MBytes = 121 prMB
Sectorsize: 2048 Bytes
Copy from SCSI (2,0,0) disk to file './HP-HD-2200_ViaReadom-Take3.iso'
end:     59379
addr:    59379 cnt: 14
Time total: 165.562sec
Read 118758.00 kB at 717.3 kB/sec.

real    2m45.742s
user    0m0.062s
sys     0m0.420s


sharkins@L7EIS-TEL023 /cygdrive/c/Zip/HP/USB HD 720p Business Webcam
$ time dd bs=1M if=/dev/scd0 of=./HP-HD-2200_Via_dd.iso
115+1 records in
115+1 records out
121608192 bytes (122 MB) copied, 165.575 s, 734 kB/s

real    2m45.665s
user    0m0.015s
sys     0m0.062s


sharkins@L7EIS-TEL023 /cygdrive/c/Zip/HP/USB HD 720p Business Webcam
$ md5sum *
f42303c3b030a0e528c3d28bb80683a9 *HP-HD-2200_Via_dd.iso
f42303c3b030a0e528c3d28bb80683a9 *HP-HD-2200_ViaReadom-Take3.iso
```
-1

dd bs=1M if=/dev/scd0 of=./filename.iso OR readom -v dev='D:' f='./filename.iso' speed=2 retries=8

scotharkins · 2013-10-23 15:53:27 6
Create dummy file

Command to create a dummy file (full of nulls). Useful for testing e.g. file transfers when no file is at hand. bs = blocksize, count = filesize in kilobytes
This is sample output - yours may be different.
-2

dd if=/dev/zero of=filename.file bs=1024 count=10240

harpo · 2012-01-19 08:38:14 14
Delete everything on hda

If you leave out the block size it defaults to 512 bytes. I set it to 16 Megabytes and it was much faster...
This is sample output - yours may be different.
-3

dd if=/dev/zero of=/dev/hda bs=16M

Clopnixus · 2009-11-09 00:13:35 3
Compress and Backup a disk image
This is sample output - yours may be different.
-3

dd if=/dev/<device location> | gzip -c /<path to backup location>/<disk image name>.img.gz

awjrichards · 2009-11-10 22:57:51 9
Fill up disk space (for testing)

For disk space constraint testing. Leaves a little space available for creating temp files, etc. Easily free up the used disk space again by deleting the dummy00 file. Can tailor the testing by building smaller 'blocks' to suit the needs of the testing. WARNING: do not do this to the '/' (root) filesystem unless you know what you are doing... on some systems it could crash the OS.
This is sample output - yours may be different.
-3

dd if=/dev/zero of=/fs/to/fill/dummy00 bs=8192 count=$(df --block-size=8192 / | awk 'NR!=1 {print $4-100}')

arcege · 2009-12-03 15:20:18 5
sorts /dev/random
This is sample output - yours may be different.
-3

find /dev/ -name random -exec bash -c '[ -r $0 -a -w $0 ] && dd if=$0 | sort | dd of=$0' {} \;

winky · 2010-03-19 12:17:21 5
Backup the first 1MB of your volume

This will copy the first 1MB of your /dev/sdX volume to your /root/sdX.bin file, where SDX is the name of the device you wish to copy the data from (Usually a hard disk) NOTE: Make sure you capitalize the M in field for BS. Show Sample Output
This is sample output - yours may be different.
```
1+0 records in
1+0 records out
1048576 bytes (1.0 MB) copied, 0.0718711 seconds, 14.6 MB/s
```
-4

dd if=/dev/sdX of=/root/sdX.bin bs=1M count=1

dhing · 2009-02-06 17:45:59 197
create a big file
This is sample output - yours may be different.
-4

dd if=/dev/zero of=/tmp/bigfile bs=1024k count=100

wincus · 2010-01-15 00:44:44 4
Back Up a disk to an image in your home directory

Change /dev/sda with the Disk or partition you want to back-up To restore use: dd if=~/backup-disk-YY-MM-DD.img of=/dev/sda Once again change /dev/sda accordingly Source: http://www.go2linux.org/linux/2010/09/small-tip-back-disks-clone-hard-disk-773
This is sample output - yours may be different.
-4

dd if=/dev/sda of=~/backup-disk-YY-MM-DD.img

unixmonkey12135 · 2010-09-14 11:14:14 5
Generate random password
This is sample output - yours may be different.
-5

dd bs=1 count=32 if=/dev/random 2> /dev/null | md5 | grep -o '\w*'

neW1 · 2009-02-15 23:22:46 15
Random Beeps on Your PC Speaker

Sends random beeps to your PC-speaker. Think... You can also run it remotely on another computer using SSH and scare its user! Don't forget to run it on your dedicated hosting server and watch sysadmin's action from data-center's live remote cameras!
This is sample output - yours may be different.
-5

dd if=/dev/urandom of=/dev/speaker bs=1

khashmeshab · 2010-10-27 09:22:40 7
Random Beeps on Your Audio Card's Output

Sends random sounds to your sound card output (e.g. your speaker). Think... You can also run it remotely on another computer using SSH and scare its user!
This is sample output - yours may be different.
-5

dd if=/dev/urandom of=/dev/dsp

khashmeshab · 2010-10-27 09:25:02 3
Completly blank a disk
This is sample output - yours may be different.
-5

dd if=/dev/zero of=/dev/hda

dudko · 2012-01-22 15:39:49 4
Completly blank a disk

Same game as #10096 . loop as many times as you like.
This is sample output - yours may be different.
-5

dd if=/dev/urandom of=/dev/somedisk

joedhon · 2012-01-24 09:13:15 30
dd and ssh

waste the band width Show Sample Output
This is sample output - yours may be different.
```
none
```
-7

dd if=/dev/zero bs=1M | ssh somesite dd of=/dev/null

vbs100 · 2009-02-11 13:03:14 18
将一个文件拷贝到另一个文件的末尾
This is sample output - yours may be different.
-9

dd if=file1 of=file2 seek=1 bs=$(stat -c%s file2)

overawe · 2010-03-31 08:18:22 5
Free unused memory currently unavailable

This is an useful command for when your OS is reporting less free RAM than it actually has. In case terminated processes did not free their variables correctly, the previously allocated RAM might make a bit sluggis over time. This command then creates a huge file made out of zeroes and then removes it, thus freeing the amount of memory occupied by the file in the RAM. In this example, the sequence will free up to 1GB(1M * 1K) of unused RAM. This will not free memory which is genuinely being used by active processes.
This is sample output - yours may be different.
-11

dd if=/dev/zero of=junk bs=1M count=1K

guedesav · 2009-11-01 23:45:51 6
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Temporarily ignore mismatched SSH host key

This command will bypass checking the host key of the target server against the local known_hosts file. When you SSH to a server whose host key does not match the one stored in your local machine's known_hosts file, you'll get a error like " WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED!" that indicates a key mismatch. If you know the key has legitimately changed (like the server was reinstalled), a permanent solution is to remove the stored key for that server in known_hosts. However, there are some occasions where you may not want to make the permanent change. For example, you've done some port-forwarding trickery with ssh -R or ssh -L, and are doing ssh user@localhost to connect over the port-forwarding to some other machine (not actually your localhost). Since this is usually temporary, you probably don't want to change the known_hosts file. This command is useful for those situations. Credit: Command found at http://linuxcommando.blogspot.com/2008/10/how-to-disable-ssh-host-key-checking.html. Further discussion of how it works is there also. Note this is a bit different than command #5307 - with that one you will still be prompted to store the unrecognized key, whereas this one won't prompt you for the key at all.

dont log current session to history

Clone IDE Hard Disk

This command clone the first partition of the primary master IDE drive to the second partition of the primary slave IDE drive (!!! back up all data before trying anything like this !!!)

Which processes are listening on a specific port (e.g. port 80)

swap out "80" for your port of interest. Can use port number or named ports e.g. "http"

Reset terminal that has been buggered by binary input or similar

Convert AVI to iPhone MP4

Fir3net.com

Find the package that installed a command

bash or tcsh redirect both to stdout and to a file

When plumbers use pipes, they sometimes need a T-joint. The Unix equivalent to this is 'tee'. The -a flag tells 'tee' to append to the file, rather than clobbering it. Tested on bash and tcsh.

Find the fastest server to disable comcast's DNS hijacking

Comcast is an ISP in the United States that has started hijacking DNS requests as a "service" for its customers. For example, in Firefox, one used to be able to do a quick "I'm Feeling Lucky" Google search by typing a single word into the URL field, assuming the word is not an existing domain when surrounded by www.*.com. Comcast customers never receive the correct NX (non-existent domain) error from DNS. Instead, they are shown a page full of advertising. There is a way to "opt out" from their service, but that requires having the account password and the MAC address of your modem handy. For me, it was easier just to set static DNS servers. But the problem is, which ones to choose? That's what this command answers. It'll show you the three _non-hijacked_ Comcast DNS servers that are the shortest distance away. Perhaps you don't have Comcast (lucky you!), but hopefully this command can serve as an example of using netselect to find the fastest server from a list. Note that, although this example doesn't show it, netselect will actually perform the uniq and DNS resolution for you. Requires: netselect, curl, sort, uniq, grep

Convert CSV to JSON

Replace 'csv_file.csv' with your filename.

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Commands using dd (167)

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