Commands using dd (167)

  • This will output the sound from your microphone port to the ssh target computer's speaker port. The sound quality is very bad, so you will hear a lot of hissing.

    dd if=/dev/dsp | ssh -c arcfour -C username@host dd of=/dev/dsp
    morpheus · 2009-02-08 10:10:00 23

  • 67
    tr -c "[:digit:]" " " < /dev/urandom | dd cbs=$COLUMNS conv=unblock | GREP_COLOR="1;32" grep --color "[^ ]"
    allinurl · 2009-06-30 17:23:49 8

  • 62
    sudo dd if=/dev/mem | cat | strings
    logik · 2009-02-09 18:29:33 9
  • Read 32GB zero's and throw them away. How fast is your system? Show Sample Output

    dd if=/dev/zero of=/dev/null bs=1M count=32768
    jacquesloonen · 2009-02-16 12:22:18 16
  • If you have some drive imaging to do, you can boot into any liveCD and use a commodity machine. The drives will be written in parallel. To improve efficiency, specify a larger block size in dd: dd if=/dev/sda bs=64k | tee >(dd of=/dev/sdb bs=64k) | dd of=/dev/sdc bs=64k To image more drives , insert them as additional arguments to tee: dd if=/dev/sda | tee >(dd of=/dev/sdb) >(dd of=/dev/sdc) >(dd of=/dev/sdd) | dd of=/dev/sde

    dd if=/dev/sda | tee >(dd of=/dev/sdb) | dd of=/dev/sdc
    nerd65536 · 2009-12-11 17:34:38 2
  • This command utilizes 'pv' to show dd's progress. Notes on use with dd: -- dd block size (bs=...) is a widely debated command-line switch and should usually be between 1024 and 4096. You won't see much performance improvements beyond 4096, but regardless of the block size, dd will transfer every bit of data. -- pv's switch, '-s' should be as close to the size of the data source as possible. -- dd's out file, 'of=...' can be anything as the data within that file are the same regardless of the filename / extension. Show Sample Output

    sudo dd if=/dev/sdc bs=4096 | pv -s 2G | sudo dd bs=4096 of=~/USB_BLACK_BACKUP.IMG
    BruceLEET · 2010-07-28 22:39:46 4
  • Create a temporary file that acts as swap space. In this example it's a 1GB file at the root of the file system. This additional capacity is added to the existing swap space. Show Sample Output

    sudo dd if=/dev/zero of=/swapfile bs=1024 count=1024000;sudo mkswap /swapfile; sudo swapon /swapfile
    dcabanis · 2009-05-27 21:10:50 1
  • read the memory from C:0000 to F:FFFF without the need auf dmidecode

    # dd if=/dev/mem bs=1k skip=768 count=256 2>/dev/null | strings -n 8
    new_user · 2010-07-02 09:38:19 1
  • This will create an exact duplicate image of your hard drive that you can then restore by simply reversing the "if" & "of" locations. sudo dd if=/media/disk/backup/sda.backup of=/dev/sda Alternatively, you can use an SSH connection to do your backups: dd if=/dev/sda | ssh dd of=~/backup/sda.backup

    sudo dd if=/dev/sda of=/media/disk/backup/sda.backup
    bandit36 · 2009-02-27 20:23:37 3
  • This line removes the 300k header from a Nero image file converting it to ISO format

    dd bs=1k if=image.nrg of=image.iso skip=300
    rpavlick · 2010-03-30 22:07:58 0

  • 12
    dd if=/dev/sda | ssh user@server 'dd of=sda.img'
    newrain7803 · 2009-10-20 06:47:01 1

  • 12
    dd if=/path/inputfile | pv | dd of=/path/outpufile
    lucafaus · 2010-12-02 18:11:42 2
  • Similar to the original, but is much faster since it only needs to write the last byte as zero. A diff on testfile and will return that they are the same.

    dd if=/dev/zero seek=5242879 bs=1 count=1
    PhillipNordwall · 2011-04-04 17:56:47 3
  • This version was mentioned in the comments. Credits go to flatcap.

    pv -tpreb /dev/urandom | dd of=file.img
    marrowsuck · 2012-04-11 22:32:52 3
  • [re]verify those burned CD's early and often - better safe than sorry - at a bare minimum you need the good old `dd` and `md5sum` commands, but why not throw in a super "user-friendly" progress gauge with the `pv` command - adjust the ``-s'' "size" argument to your needs - 700 MB in this case, and capture that checksum in a "test.md5" file with `tee` - just in-case for near-future reference. *uber-bonus* ability - positively identify those unlabeled mystery discs - for extra credit, what disc was used for this sample output? Show Sample Output

    dd if=/dev/cdrom | pv -s 700m | md5sum | tee test.md5
    asmoore82 · 2009-03-09 00:11:42 1
  • Running this code will execute dd in the background, and you'll grab the process ID with '$!' and assign it to the 'pid' variable. Now, you can watch the progress with the following: while true; do kill -USR1 $pid && sleep 1 && clear; done The important thing to grasp here isn't the filename or location of your input or output, or even the block size for that matter, but the fact that you can keep an eye on 'dd' as it's running to see where you are at during its execution.

    dd if=/dev/urandom of=file.img bs=4KB& pid=$!
    atoponce · 2009-04-08 05:56:47 9
  • A dear friend of mine asked me how do I copy a DVD to your hard drive? If you want to make a copy of the ISO image that was burned to a CD or DVD, insert that medium into your CD/DVD drive and (assuming /dev/cdrom is associated with your computer?s CD drive) type the following command

    dd if=/dev/cdrom of=whatever.iso
    0disse0 · 2009-09-05 09:19:41 3
  • piping through 'pv' shows a simple progress/speed bar for dd. This is a replacement for my otherwise favorite 'while :;do killall -USR1 dd;sleep 1;done' Show Sample Output

    dd if=/dev/nst0 |pv|dd of=restored_file.tar
    oernii2 · 2010-04-07 09:21:18 10

  • 9
    dd if=/dev/zero | pv | dd of=/dev/null
    richard · 2010-05-14 16:58:42 2
  • In addition to a swap partition, Linux can also use a swap file. Some programs, like g++, can use huge amounts of virtual memory, requiring the temporary creation of extra space.

    dd if=/dev/zero of=/swapfile bs=1M count=64; chmod 600 /swapfile; mkswap /swapfile; swapon /swapfile
    starchox · 2009-02-16 18:36:38 1
  • This command securely erases all the unused blocks on a partition. The unused blocks are the "free space" on the partition. Some of these blocks will contain data from previously deleted files. You might want to use this if you are given access to an old computer and you do not know its provenance. The command could be used while booted from a LiveCD to clear freespace space on old HD. On modern Linux LiveCDs, the "ntfs-3g" system provides ReadWrite access to NTFS partitions thus enabling this method to also be used on Wind'ohs drives. NB depending on the size of the partition, this command could take a while to complete. Show Sample Output

    # cd $partition; dd if=/dev/zero of=ShredUnusedBlocks bs=512M; shred -vzu ShredUnusedBlocks
    mpb · 2009-06-21 14:17:22 7
  • Create an image of "device" and send it to another machine through the network ("target" and "port" sets the ip and port the stream will be sent to), outputting a progress bar On the machine that will receive, compress and store the file, use: nc -l -p <port> | 7z a <filename> -si -m0=lzma2 -mx=9 -ms=on Optionally, add the -v4g switch at the end of the line in order to split the file every 4 gigabytes (or set another size: accepted suffixes are k, m and g). The file will be compressed using 7z format, lzma2 algorithm, with maximum compression level and solid file activated. The compression stage will be executed on the machine which will store the image. It was planned this way because the processor on that machine was faster, and being on a gigabit network, transfering the uncompressed image wasn't much of a problem.

    dd if=<device> | pv | nc <target> <port>
    quitaiskiluisf · 2012-01-27 18:37:36 5

  • 7
    dd if=/dev/sda5 bs=2048 conv=noerror,sync | gzip -fc | lftp -u user,passwd domain.tld -e "put /dev/stdin -o backup-$(date +%Y%m%d%H%M).gz; quit"
    sputnick · 2009-05-29 21:56:32 0
  • Solves "tr" issues with non C-locales under BSD-like systems (like OS X)

    LC_ALL=C tr -c "[:digit:]" " " < /dev/urandom | dd cbs=$COLUMNS conv=unblock | GREP_COLOR="1;32" grep --color "[^ ]"
    zzambia · 2009-07-02 07:10:33 2
  • This invokes tar on the remote machine and pipes the resulting tarfile over the network using ssh and is saved on the local machine. This is useful for making a one-off backup of a directory tree with zero storage overhead on the source. Variations on this include using compression on the source by using 'tar cfvp' or compression at the destination via ssh user@host "cd dir; tar cfp - *" | gzip - > file.tar.gz

    ssh user@host "cd targetdir; tar cfp - *" | dd of=file.tar
    bwoodacre · 2009-03-18 07:43:22 3
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List just the executable files (or directories) in current directory
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Reset hosed terminal,
stty sane resets the tty to basic usable function. The ^J is a newline -- sometimes CR/LF interpretation is broken so use the ^J explicitly.

blktrace - generate traces of the i/o traffic on block devices
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Stat each file in a directory
This will run stat on each file in the directory.

See why a program can't seem to access a file
Sometimes a program refuses to read a file and you're not sure why. You may have display_errors turned off for PHP or something. In this example, fopen('/var/www/test/foo.txt') was called but doesn't have read access to foo.txt. Strace can tell you what went wrong. E.g., if php doesn't have read access to the file, strace will say "EACCESS (Permission denied)". Or, if the file path you gave doesn't exist, strace will say "ENOENT (No such file or directory)", etc. This works for any program you can run from the command-line, e.g., strace python -e open,access... Note: the above command uses php-cli, not mod_php, which is a different SAPI with diff configs, etc.

Convert seconds to [DD:][HH:]MM:SS
Converts any number of seconds into days, hours, minutes and seconds. sec2dhms() { declare -i SS="$1" D=$(( SS / 86400 )) H=$(( SS % 86400 / 3600 )) M=$(( SS % 3600 / 60 )) S=$(( SS % 60 )) [ "$D" -gt 0 ] && echo -n "${D}:" [ "$H" -gt 0 ] && printf "%02g:" "$H" printf "%02g:%02g\n" "$M" "$S" }

DELETE all those duplicate files but one based on md5 hash comparision in the current directory tree
This one-liner will the *delete* without any further confirmation all 100% duplicates but one based on their md5 hash in the current directory tree (i.e including files in its subdirectories). Good for cleaning up collections of mp3 files or pictures of your dog|cat|kids|wife being present in gazillion incarnations on hd. md5sum can be substituted with sha1sum without problems. The actual filename is not taken into account-just the hash is used. Whatever sort thinks is the first filename is kept. It is assumed that the filename does not contain 0x00. As per the good suggestion in the first comment, this one does a hard link instead: $ find . -xdev -type f -print0 | xargs -0 md5sum | sort | perl -ne 'chomp; $ph=$h; ($h,$f)=split(/\s+/,$_,2); if ($h ne $ph) { $k = $f; } else { unlink($f); link($k, $f); }'

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