Master Linux dd: Copy, Backup, and Transform Files with Powerful Commands

Copy Files

The dd command can be used to copy a file from one location to another. dd if=input.txt of=output.txt This copies the contents of input.txt to output.txt.

Backup and Restore Disks

dd

can create a full backup of a disk and restore that backup to a new disk.

# Create a disk backup
dd if=/dev/sda of=backup.img bs=4M

The command copies the entire content of /dev/sda into the file backup.img.

# Restore the backup to a new disk
dd if=backup.img of=/dev/sdb bs=4M

This copies the data from backup.img to the new disk /dev/sdb.

Generate Random Data

dd

can also generate files filled with random data.

dd if=/dev/urandom of=random_data.bin bs=1M count=10

The result is a file random_data.bin containing 10 MiB of random bytes.

Adjust Block Size

By specifying the bs (block size) parameter, you can control the block size used by dd, which can affect copy performance.

dd if=input.txt of=output.txt bs=1K

Show Progress Information

To display progress while dd runs, add the status=progress option.

dd if=input.txt of=output.txt bs=1M status=progress

This prints the number of bytes transferred and the transfer speed.

Skip and Truncate Data

dd

can skip a portion of the input file or truncate the output. dd if=input.txt of=output.txt bs=1G skip=1 This skips the first 1 GiB of input.txt and writes the remainder to output.txt.

Modify File Size

You can truncate or extend a file to a specific size using seek or count. dd if=/dev/null of=output.txt bs=1M seek=100 This creates (or truncates) output.txt to exactly 100 MiB; any excess data is discarded.

Convert Data Format While Copying

dd

can perform on‑the‑fly data conversion. For example, converting all text to uppercase: dd if=input.txt of=output.txt conv=ucase The command reads from input.txt, converts the data to uppercase, and writes it to output.txt.

Skip the Beginning of an Input File

The skip parameter lets you ignore the first part of the input file. dd if=input.txt of=output.txt bs=1G skip=1 This reads input.txt, skips the first 1 GiB, and writes the rest to output.txt.

Limit the Amount of Data Copied

You can restrict dd to copy only a specific amount of data. dd if=input.txt of=output.txt bs=1G count=5 This copies the first 5 GiB from input.txt to output.txt.

Summary

The dd command is a powerful Linux utility for copying, converting, generating, and modifying file and device data. Its versatility makes it useful for many tasks, but incorrect parameters can cause data loss, so always verify the command before execution.