dd

Convert and copy a file.

TL;DR

N and BYTES values may be followed by the following multiplicative suffixes:

suffix	multiplication
`c`	1
`w`	2
`b`	512
`kB`	1000
`K`	1024
`MB`	1000 * 1000
`M` or `xM`	1024 * 1024
`GB`	1000 * 1000 * 1000
`G`	1024 * 1024 * 1024

and so on for T, P, E, Z, Y.

# Read 512 random Bytes for each iteration and save them.
dd if='/dev/urandom' of='output/file' count=2 bs=512

# Read 1000 Bytes for each iteration and save them while watching the progress.
dd if='/input/file' of='output/file' count=4M bs=1k status='progress'

# Create a 1GiB file with nothing but zeros, ready to mkswap(8) it.
dd if='/dev/zero' of='/swapfile' count=1048576 bs=1024

# Make a bootable USB drive from an isohybrid file.
dd if=file.iso of=/dev/usb_drive status=progress

# Clone a drive to another drive with 4 MiB block.
# Ignore any error and show the progress.
dd if=/dev/source_drive of=/dev/dest_drive bs=4M conv=noerror status=progress

# Generate a system backup into an IMG file and show the progress:
dd if=/dev/drive_device of=path/to/file.img status=progress

# Restore a drive from an IMG file and show the progress:
dd if=path/to/file.img of=/dev/drive_device status=progress

# Create images from disks.
sudo dd if=/dev/mmcblk0 of=/tmp/mmcblk0.img conv=sync bs=4k
sudo dd if=/dev/sda conv=sync,noerror bs=64K | gzip -c > /mnt/sdb/disk.img.gz

# Write an image to disk.
sudo dd if=/tmp/mmcblk0.img of=/dev/mmcblk0 conv=fsync oflag=direct bs=4M status=progress

# Clone a disk on another disk.
sudo dd if=/dev/sda of=/dev/sdb conv=fsync bs=4M oflag=direct status=progress

Benchmark disks

Use:

a single, bigger file for throughput (write speed)
multiple, smaller files for latency

dd \
  if=/dev/input.file of=/path/to/output.file \
  bs=block-size count=number-of-blocks \
  oflag=dsync status=progress

Examples:

dd if=/dev/zero of=/tmp/test1.img bs=1G count=1 oflag=dsync
dd if=/dev/zero of=/tmp/test2.img bs=64M count=1 oflag=dsync
dd if=/dev/zero of=/tmp/test3.img bs=1M count=256 conv=fdatasync
dd if=/dev/zero of=/tmp/test4.img bs=8k count=10k
dd if=/dev/zero of=/tmp/test4.img bs=512 count=1000 oflag=dsync

Sources

All the references in the [further readings] section, plus the following:

2.9 KiB Raw Blame History

dd

TL;DR

Benchmark disks

Further readings

Sources

2.9 KiB

Raw Blame History