Recipe: Loopback files and mounting 

Note: Most of the commands in this file are to be executed as root. Hence the shell is "#"

Create an ext4 filesystem on a file of size 1GB
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$ dd if=/dev/zero of=loobackfile.img bs=1G count=1
1024+0 records in 
1024+0 records out 
1073741824 bytes (1.1 GB) copied, 37.3155 s, 28.8 MB/s

# mkfs.ext4 loopbackfile.img

$ sudo file loobackfile.img 
loobackfile.img: Linux rev 1.0 ext4 filesystem data, UUID=c9d56c42-f8e6-4cbd-aeab-369d5056660a (extents) (large files) (huge files)

Loopback mounting
=================
$ sudo mkdir /mnt/loopback
# mount -o loop loopback.img /mnt/loopback


Alternate way to mount loopback device
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# losetup /dev/loop1 loopback.img
# mount /dev/loop1 /mnt/loopback

# losetup /dev/loop1 loopback.img
# fdisk /dev/loop1



# losetup -o 32256 /dev/loop2 loopback.img
## With offset

unmount
=======
# umount mountpoint

Mount ISO file as loopback
==============================

# mkdir /mnt/iso
# mount -o loop linux.iso /mnt/iso

Flush changes immediately with sync
===================================
# sync