Mastering Linux dd: Powerful Data Copy, Backup, and Disk Operations

dd is a Linux/Unix utility for low‑level I/O, allowing block‑size‑specified copying and conversion of files.

Parameters

if=FILE      # input file, default stdin
of=FILE      # output file, default stdout
ibs=SIZE     # input block size (default 512)
obs=SIZE     # output block size (default 512)
bs=SIZE      # both input and output block size (overrides ibs/obs)
count=N      # copy only N input blocks
status=LEVEL # progress display level (none, noxfer, progress)
iflag=FLAGS  # input flags (append, direct, etc.)
oflag=FLAGS  # output flags
conv=OPTIONS # conversion options (ascii, ebcdic, lcase, ucase, sync, …)

Common Examples

# Backup partition /dev/vdb1 to /dev/vdb2
dd if=/dev/vdb1 of=/dev/vdb2 status=progress

# Backup to a file
dd if=/dev/vdb1 of=/opt/backupsFile.back status=progress

# Restore from backup file
dd if=/opt/backupsFile.back of=/dev/vdb1 status=progress

# Create a 1 GB file (e.g., swap file)
dd if=/dev/zero of=/tmp/swapFile bs=1M count=1024 status=progress

# Compress a partition backup
dd if=/dev/vdb1 status=progress | gzip > /opt/backups.gz

# Decompress and restore
gzip -dc /opt/backups.gz | dd of=/dev/vdb2 status=progress

# Generate a 10 M test file
dd if=/dev/zero of=/tmp/testFile bs=1M count=10

# Test disk write speed
timeout 120 dd if=/dev/zero of=/tmp/speed.dat bs=2M count=1000 oflag=direct

# Test disk read speed
timeout 120 dd if=/tmp/speed.dat of=/dev/null bs=2M count=1000 status=progress

# Create a bootable USB from an ISO
sudo dd if=ubuntu-23.10.1-desktop-amd64.iso of=/dev/sdb status=progress

# Backup MBR (first 512 bytes)
dd if=/dev/vda of=/opt/mbr.bak bs=512 count=1

# Restore MBR
dd if=/opt/mbr.bak of=/dev/vda bs=512 count=1

Additional Notes

Use conv=lcase or conv=ucase to change character case, conv=sync to pad blocks, and conv=sparse to create sparse files. /dev/zero provides an endless stream of zero bytes, while /dev/null discards all output.