What is dd?
The dd command is a powerful utility in Linux used for copying and converting data at the block level, often employed for tasks like creating disk images, cloning disks, securely wiping data, and more.
Essential Commands and Subcommands
Note: dd command uses operands that how data is read, written, or converted.
| Option | Description |
|---|---|
if= | Input file (source) |
of= | Output file (destination) |
bs= | Block size for reading/writing(eg:1M for 1 megabytes) |
count= | Number of blocks to coyp |
skip= | Skip a specified number of blocks at the start of the input |
seek= | Skip a specified number of blocks at the start of the output |
status= | Control progress display(progres, noxfer, none) |
conv= | Apply data conversions (eg: sync, noerror, notrunc) |
iflag= | Input flags (eg: direct, fullblock) |
oflag= | Output flags (eg: direct, sync) |
Exercises
- Create a file filled with zeros:
dd if=/dev/zero of=file.txt bs=1M count=100
- Copy a disk partition to a file:
dd if=/dev/sda1 of=backup.img bs=4M
- Restore a disk image to a partition:
dd if=backup.img of=/dev/sda1 bs=4M
- Create a bootable USB drive:
dd if=ubuntu.iso of=/dev/sdb bs=4M status=progresser
- Copy only part of a file:
dd if=/dev/zero of=largefile.img bs=1M count=10 #create a file with zeros
dd if=largefile.img of=partfile.img bs=1M count=1 #let copy part of the file for 1mb
- Wipe a File(Overwrite with zeros/randomly):
dd if=/dev/zero of=partfile.img bs=1M
#keep on filling zero until it reaches the original size of the file
dd if=/dev/urandom of=partfile.img bs=1M
#keeps filling random data until it reaches the original size of the file
- Backup the Master Boot Record (MBR)
sudo dd if=/dev/sda of=mbr_backup.img bs=512 count=1
- Restore the Master Boot Record from Backup
sudo dd if=mbr_backup.img of=/dev/sda bs=512 count=1
- Monitor Progress of a Large Copy
dd if=largefile.img of=largefile_copy.img bs=1M status=progress