Master raw copying, imaging and simple backups with dd. 05.03.2026 | reading time: 2 min When a sector-perfect copy or a raw image is needed, dd reads and writes bytes from devices and files without interpreting them; that makes dd the essential low-level copy tool and also one to respect and use with caution. Clone a USB stick and verify Make a bit-for-bit image of a USB stick and check its checksum with these commands: ``` sudo dd if=/dev/sdb of=usb.img bs=4M conv=noerror,sync status=progress md5sum usb.img ``` Sample output might look like: ``` 41943040 bytes (42 MB, 40 MiB) copied, 1.02 s, 41.1 MB/s d41d8cd98f00b204e9800998ecf8427e usb.img ``` This produces an exact image; to inspect partitions, attach it with `losetup` and map partitions with `kpartx` or mount loop devices. Options that change everything Use `bs` to tune throughput, `count` to limit bytes, and `skip`/`seek` to offset input or output; combine `conv=noerror,sync` to continue on read errors and pad blocks, `iflag=fullblock` to ensure full reads, `oflag=direct` to bypass caches and `status=progress` to monitor activity; always double-check `if` and `of` to avoid destroying data and consider `pv` or `status=progress` for human-friendly progress reporting. When dd is not the best choice For damaged disks prefer `ddrescue` which specializes in recovery, for file-level copying use `rsync`, and for imaging partitions with metadata preserved consider `partclone` or filesystem-aware tools; dd stays useful for raw images, creating files filled with zeros or random data, and testing I/O performance. A final direction Practice safely: run dd on test images, script verification steps, and include checksums in workflows; then deepen system knowledge with structured study and consider certifications such as CompTIA Linux+ or LPIC-1 and intensive exam preparation at bitsandbytes.academy to turn command-line skill into certified competence. Join Bits & Bytes Academy First class LINUX exam preparation. utilities storage backup filesystem troubleshooting
