Hi All,

I read online an article about using loop device to create a filesystem out of a file. The procedure is as following:

"
Create a file of a hundred mega-bytes:
dd bs=1M count=100 if=/dev/zero of=output
Format the file:
mkfs.ext2 output
Mount the file with a loop device:
mkdir loop-mount
mount -o loop output loop-mount
When using the option ”-o loop” the first available loop device is taken. It is possible to select the loop device to use by giving the option ”-o loop=/dev/loop0”.
"

After mounting the newly created fs, I am able to go into the fs and do things such as creating a new directory. My question is, even though the title is "Using loop device to create a filesystem", I don't see any involvement of the loop device here when I am using the fielsystem. Could someone explain what role the loop device plays here?

Thanks,
Wei Xu

The freshly created filesystem is mounted using loop device.

After creating the filesystem for the file called output, create or use a loop device like so. In this example I will be using using loop1. Must be root.

To mount the filesystem, type
/mnt is use here as an example of the mount point.

When done using the filesystem, unmount it and unmap the loop device.
I use this method myself but I use an encrypted file to mount with a loop device.

Hope this helps

The loop device is used to translate block read/write requests into offsets into the file. Effectively it maps the file into the definition of a partition.