System and processes

The dd command

Copies data at a low level, block by block. Used to clone disks, create images and fill files.

Syntax

dd if=ORIGEN of=DESTINO [bs=TAMAÑO] [count=N]

Most useful options

if=Input file or device
of=Output file or device
bs=Block size
count=Number of blocks to copy

Copy-ready examples

$ printf 'datos\n' > a.txt && dd if=a.txt of=b.txtCopy a file
$ dd if=/dev/zero of=ceros.bin bs=1 count=4Create 4 zero bytes

You can try them in the browser terminal: it does not touch your computer.

Typical mistakes

  • With if/of it is easy to slip and overwrite a whole disk: always double-check the of=.

Related commands

cptarmount

FAQ

What is dd actually used for?

To clone disks, create bootable USB sticks or generate test files.

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