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As a beginner I am learning the basics use of command line. While exploring I get to know about "dd" command . I am not sure about the utility of this command as a beginner. Kindly explain me in simple words usage of this command

Rana Zuhair
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    Why don't you man dd to read the reference manual page... It provides "convert and copy a file" as the quick description, and more details beyond that too. Do your own homework... – guiverc Sep 03 '22 at 13:32
  • just FYI: I firstly learnt the command as data dump... as it was the command that was used to write file(s) to tape, or read files back from tape... (old magnetic tape of long ago) – guiverc Sep 03 '22 at 13:41
  • If the man pages seem like too much for you, you could also check quick common usage with the tldr command, or you can search about it too.

    Simply dd can "Convert and copy a file", it is a quite versatile command (because everything on Linux is a file) and can be dangerous if misused. So I suggest you to use cp or mv instead.

     – td211 Sep 03 '22 at 13:44
  • I was told it was Disk Destroyer when I 1st heard of it :D :D – Rinzwind Sep 03 '22 at 13:44
  • Tempted to -1 due to lack of research effort. Google will happily explain what dd is, what it does, when it is appropriately used, and even provide it's history. – user535733 Sep 03 '22 at 14:57

2 Answers2

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  • Backup and restore a hard drive or partition.
  • Backup images of CD or DVDs; Creating a virtual file system.

There are a lot more. 2 others:

  • Copy regions of raw device files
  • Converting files. Like data formats (ascii to ebcdic) or to all lowercase/uppercase

A very useful use case for the 1st option: if you have a backup of a whole partition/disk you can use recovery tools like testdisk to try and restore deleted content. If you do that on the actual system a single write could kill the success rate.

The 2nd one lets you create an ISO from for instance cd, dvd, or bd. You can then mount it and play the music or the video without the need of the disk.

Rinzwind
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Basically, it's a command that can directly copy data from "anything" to "anything". "Anything" can be for example your whole disk or a partition, and this command does not check what the target "anything" is and just overwrites it with the source; so EXTREME CAUTION is recommended when using this command as you can easily destroy data. In short: don't use it if you don't know exactly what this particular instance of the command, with these particular parameters does.

Having said that, nowadays the most common use of this command is to create an image of your whole disk, or a partition, for backup purposes. This is not for your daily data backup, but for so called "disaster recovery". If any disaster happens to your system and everything gets deleted, if you have such an image (on an external disk of course), you can restore your disk or partition to the exact same state as it was when the image has been created.

raj
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