dd if=/dev/sda of=/media/external_media/sda.img

mount -t ext4 -o loop /media/external_media/sda.img /media/sda_image

$ sudo fdisk -lu sda.img
...
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
...
  Device Boot      Start         End      Blocks   Id  System
sda.img1   *          56     6400000     3199972+   c  W95 FAT32 (LBA)

sudo losetup -o 28672 /dev/loop0 sda.img

sudo fsck -fv /dev/loop0
sudo mount /dev/loop0 /mnt

sudo umount /mnt
sudo losetup -d /dev/loop0

sudo losetup -Pf disk_image.raw

$ sudo kpartx -av disk_image.raw
add map loop0p1 (252:2): 0 3082240 linear /dev/loop0 2048
add map loop0p2 (252:3): 0 17887232 linear /dev/loop0 3084288

$ sudo mount /dev/mapper/loop0p2 /mnt

$ sudo umount /mnt
$ sudo kpartx -d disk_image.raw

-P, --partscan
          force kernel to scan partition table on newly created loop device

$ sudo losetup -f --show -P /path/to/image.img

$ los my.img
/dev/loop0
/mnt/loop0p1
/mnt/loop0p2

$ ls /mnt/loop0p1
/whatever
/files
/youhave
/there

$ sudo losetup -l
NAME       SIZELIMIT OFFSET AUTOCLEAR RO BACK-FILE                                                                                      DIO
/dev/loop1         0      0         0  0 /full/path/to/my.img

$ # Cleanup.
$ losd 0
$ ls /mnt/loop0p1
$ ls /dev | grep loop0
loop0

los() (
  img="$1"
  dev="$(sudo losetup --show -f -P "$img")"
  echo "$dev"
  for part in "$dev"?*; do
    if [ "$part" = "${dev}p*" ]; then
      part="${dev}"
    fi
    dst="/mnt/$(basename "$part")"
    echo "$dst"
    sudo mkdir -p "$dst"
    sudo mount "$part" "$dst"
  done
)
losd() (
  dev="/dev/loop$1"
  for part in "$dev"?*; do
    if [ "$part" = "${dev}p*" ]; then
      part="${dev}"
    fi
    dst="/mnt/$(basename "$part")"
    sudo umount "$dst"
  done
  sudo losetup -d "$dev"
)

cat /sys/module/loop/parameters/max_part

options loop max_part=31

GRUB_CMDLINE_LINUX="loop.max_part=31"

sudo losetup -f --show my.img

# sudo losetup /dev/loop2 sda.img

# sudo mdadm --build --level=0 --force --raid-devices=1 /dev/md2 /dev/loop2
mdadm: array /dev/md2 built and started.

nile-172-b0fef38-76:/mnt/sdb1 # ls -l /dev/md2*
brw-rw---- 1 root disk   9, 2 Oct 10 12:37 /dev/md2
brw-rw---- 1 root disk 259, 0 Oct 10 12:37 /dev/md2p1

fdisk -l $IMAGE
# calculate the offset in bytes
mount -o loop,offset=$OFFSET $IMAGE $MOUNTPOINT

mountimg /media/external_media/sda.img 2 /media/sda_image

mountimg /media/external_media/sda.img 2 /media/sda_image -t vfat -o codepage=866,iocharset=utf-8

umount /media/sda_image