The DD file is a disk image file and a replica of a hard disk drive.
The file that has a .dd extension is usually created with an imaging tool called DD.
The utility provides a command line interface to create disk images on a system running UNIX and GNU/LINUX OS.
To see what structure the file has, you can use fdisk:
sudo fdisk -l file.dd
fdisk shows only the type of partition but not the file system to know it is necessary to use cfdisk.
sudo cfdisk file.dd
So we will know what file system it is.
To know where the partition to mount begins in bytes, it is necessary to see the Start column.
Assuming you start at sector 92408 and each sector is 512 bytes.
The beginning of the partition in bytes will be 92408 * 512, this is what is known as offset.
The shell can do the necessary multiplication to calculate the offset by typing
$((92408 * 512))
Once we have everything we need, we are going to mount a dd image by typing:
sudo mount -t filesystem -o loop, ro, offset = $ ((start * 512)) file.dd mount_point
-t: we indicate the file system
-o: indicates options for mount
loop: it is necessary to convert a static image into a dynamic image.
ro: is in read mode (read-only)
offset: indicates where the partition to mount begins in bytes
start: is the data corresponding to the start column of fdisk or cfdisk