Commands using dd (146)

  • See: http://imgur.com/JgjK2.png for example. Do some serious benchmarking from the commandline. This will write to a file with the time it took to compress n bytes to the file (increasing by 1). Run: gnuplot -persist <(echo "plot 'lzma' with lines, 'gzip' with lines, 'bzip2' with lines") To see it in graph form.


    3
    for a in bzip2 lzma gzip;do echo -n>$a;for b in $(seq 0 256);do dd if=/dev/zero of=$b.zero bs=$b count=1;c=$(date +%s%N);$a $b.zero;d=$(date +%s%N);total=$(echo $d-$c|bc);echo $total>>$a;rm $b.zero *.bz2 *.lzma *.gz;done;done
    matthewbauer · 2009-10-20 01:00:51 2

  • 1
    time dd if=/dev/zero of=TEST bs=4k count=512000
    flojb · 2009-10-17 17:50:53 3
  • Intentional hash in the beginning. May run a looong time. Wipes your data for real. Was meant to be /dev/urandom - I mistyped it. :-)


    2
    # for i in $(seq 1 25); do dd if=/dev/urandom of=<your disk> bs=1M ; done
    danam · 2009-09-29 07:12:34 3
  • You can use this to directly dump from machine A (with dvd drive) to machine B (without dvd drive) . I used this to copy dvd using my friend's machine to my netbook. Above command is to be issued on machine B. Advantages : 1) No wasting time dumping first to machine A and then copying to Machine B. 2) You dont need to use space on Machine A. In fact, this will work even when Machine A doesnt have enough hdd space to dump the DVD. Use -C ssh option on slow networks (enables compression). you can replace "dd if=/dev/dvd" with any ripping command as long as it spews the iso to stdout.


    5
    ssh user@machine_A dd if=/dev/dvd0 > dvddump.iso
    kamathln · 2009-09-11 18:08:36 5
  • Overwrites the boot sector. Since this doesn't overwrite any data, you can usually recover by re-creating the partition table exactly the same as before you zeroed it. This can also help sometimes if you install a new drive in a Windows machine which can't read it.


    2
    dd if=/dev/zero of=/dev/fd0 bs=512 count=1
    andrew112358 · 2009-09-09 23:43:22 0
  • 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


    8
    dd if=/dev/cdrom of=whatever.iso
    0disse0 · 2009-09-05 09:19:41 3
  • 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 !!!)


    5
    sudo dd if=/dev/hda1 of=/dev/hdb2
    0disse0 · 2009-09-05 09:16:52 0

  • -1
    echo capitalize | { dd bs=1 count=1 conv=ucase 2> /dev/null; cat ;}
    twfcc · 2009-09-05 01:49:53 1

  • 5
    dd bs=1 seek=2TB if=/dev/null of=ext3.test
    Superhuman · 2009-09-03 08:35:20 0

  • 0
    dd if=/dev/urandom count=200 bs=1 2>/dev/null | tr "\n" " " | sed 's/[^a-zA-Z0-9]//g' | cut -c-16
    amaymon · 2009-08-07 06:32:55 2
  • Create a bunch of random files with random binary content. Basically dd dumps randomly from your hard disk to files random-file*. Show Sample Output


    0
    no_of_files=10; counter=1; while [[ $counter -le $no_of_files ]]; do echo Creating file no $counter; dd bs=1024 count=$RANDOM skip=$RANDOM if=/dev/sda of=random-file.$counter; let "counter += 1"; done
    rajaseelan · 2009-07-31 16:34:47 2
  • Same as above but slooooow it down


    2
    while true ; do IFS="" read i; echo "$i"; sleep .01; done < <(tr -c "[:digit:]" " " < /dev/urandom | dd cbs=$COLUMNS conv=unblock | GREP_COLOR="1;32" grep --color "[^ ]")
    friedchuckles · 2009-07-22 03:59:07 1
  • Let dd use direct I/O to write directly to the disk without any caching. You'll encounter very different results with different block sizes (try with 1k, 4k, 1M, ... and appropriate count values).


    0
    time dd if=/dev/zero of=blah.out oflag=direct bs=256M count=1
    olorin · 2009-07-15 07:17:32 0
  • Note, the [remotePort] should be opened in the firewall first. First, start the destination box listening, then fire off the sending box. Data from the /dev/zero device in memory of the source machine is read out using dd, sent over the network with nc, and read back in from the other side of the network with nc, going to the /dev/null device. Essentially, it is a memory-network-memory copy operation, the output of dd will tell you how fast your network really is performing.


    0
    dd if=/dev/zero bs=256M count=1 | nc [remoteIP] [remotePort] and on the other host nc -l port >/dev/null
    tkunz · 2009-07-14 20:30:52 1
  • Depending on the speed of you system, amount of RAM, and amount of free disk space, you can find out practically how fast your disks really are. When it completes, take the number of MB copied, and divide by the line showing the "real" number of seconds. In the sample output, the cached value shows a write speed of 178MB/s, which is unrealistic, while the calculated value using the output and the number of seconds shows it to be more like 35MB/s, which is feasible. Show Sample Output


    2
    time (dd if=/dev/zero of=blah.out bs=256M count=1 ; sync )
    tkunz · 2009-07-14 20:19:23 3

  • 1
    # dd if=/dev/sda | gzip -c | ssh user@ip 'dd of=/mnt/backups/sda.dd'
    coolman · 2009-07-06 19:05:55 2
  • Solves "tr" issues with non C-locales under BSD-like systems (like OS X)


    7
    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 1

  • 64
    tr -c "[:digit:]" " " < /dev/urandom | dd cbs=$COLUMNS conv=unblock | GREP_COLOR="1;32" grep --color "[^ ]"
    allinurl · 2009-06-30 17:23:49 7
  • 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


    8
    # cd $partition; dd if=/dev/zero of=ShredUnusedBlocks bs=512M; shred -vzu ShredUnusedBlocks
    mpb · 2009-06-21 14:17:22 6
  • This will create a 10 MB file named testfile.txt. Change the count parameter to change the size of the file. As one commenter pointed out, yes /dev/random can be used, but the content doesn't matter if you just need a file of a specific size for testing purposes, which is why I used /dev/zero. The file size is what matters, not the content. It's 10 MB either way. "Random" just referred to "any file - content not specific" Show Sample Output


    1
    dd if=/dev/zero of=testfile.txt bs=1M count=10
    mstoecker · 2009-06-17 17:06:16 7
  • This shell snippet reads a single keypress from stdin and stores it in the $KEY variable. You do NOT have to press the enter key! The key is NOT echoed to stdout! This is useful for implementing simple text menus in scripts and similar things.


    5
    stty cbreak -echo; KEY=$(dd bs=1 count=1 2>/dev/null); stty -cbreak echo
    inof · 2009-06-09 13:15:49 4
  • If you don't want your computer to try to boot form a USB stick that used to be used as a boot device (maybe for a live linux distro), you will have to remove the boot loader from your stick other wise the boot will fail each time the device is attached to your PC.


    0
    dd if=/dev/zero of=/dev/sdb bs=446 count=1
    dcabanis · 2009-06-07 10:29:49 1

  • 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
  • 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


    18
    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

  • 1
    dd if=/dev/mem of=file.dump bs=1024 skip=0 count=1
    professoralex · 2009-05-11 00:19:50 1
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