dd

Convert and copy raw data

high risk

interactive breakdown — edit the command and press Explain
$ 
⚠ Risks & cautions
Safer / dry-run alternatives
lsblk -o NAME,SIZE,MODEL,MOUNTPOINTVerify the target device
ddrescue <src> <dst> mapUse ddrescue for failing disks
pv file.iso | dd of=/dev/sdX bs=4MShow progress via pv
What it does

Copies blocks from input to output — used for disk images, boot media and benchmarking.

Common flags
FlagMeaning
if=Input file/device
of=Output file/device (DANGEROUS)⚠ A wrong of= overwrites data with no prompt.
bs=Block size
status=progressShow progress
conv=fsyncFlush data before exit
count=Number of blocks
Examples
dd if=/dev/sda of=disk.img bs=4M status=progressImage a disk · explain & risk-check →
dd if=ubuntu.iso of=/dev/sdX bs=4M status=progress conv=fsyncWrite an ISO to a USB stick · explain & risk-check →
Related
lsblk mkfs ddrescue
Open the full explainer →More in Disks & Filesystems

Reference text is hand-written and may be incomplete — check man dd for your version. Test destructive commands on a non-production system first.