dd Command in Linux

Linux dd Command Syntax

The syntax for the dd command is as follows:

Where:

• if: Specifies the input file to be used.
• of: Specifies the output file to be created or overwritten.

dd Command Options:

• bs: Sets the block size for input and output in bytes (default is 512).
• count: Copies only a specific number of input blocks.
• seek: Skips a specified number of output blocks before writing.
• skip: Skips a specified number of input blocks before reading.

Example Usages

• Create a bootable USB drive from an ISO file.:

  Output:

  Explanation: The command takes input.iso as the input file, writes it to /dev/sdb (the USB drive), with a block size of 4M and displays progress.

• Backup an entire disk to an image file.:

  Output:

  Explanation: The command takes /dev/sda as the input file (the entire disk), writes it to backup.img, with a block size of 4M and displays progress.

Advanced Use Cases of dd Command in Linux

• Convert a file from lowercase to uppercase.:

  Output:

  Explanation: The command takes input.txt as the input file, writes it to output.txt, and converts all lowercase characters to uppercase using the conv=ucase option.

• Create a 1GB file filled with zeros.:

  Output:

  Explanation: The command reads from /dev/zero (a special file that produces null characters), writes it to 1GBfile.img, with a block size of 1M and a count of 1024 (1GB).

• Securely erase a disk.:

  Output:

  Explanation: The command reads from /dev/urandom (a special file that produces random data), writes it to /dev/sda (the disk), with a block size of 4M, effectively overwriting the entire disk with random data.