> Create Linux Filesystem From An Ordinary File
> Under Linux, you can create a regular file, format it as an ext2,
> ext3, or reiser filesystem, and then mount it just like a
> physical drive. It's then possible to read and write files to
> this newly-mounted device. You can also copy the complete
> filesystem, since it is just a file, to another computer.
> First, you want to create a 20MB file or any size you want by
> executing the following command:
> $ dd if=/dev/zero of=disk-image count=40960
> 40960+0 records in
> 40960+0 records out
> Next, to format this as an ext3 filesystem, you just execute the
> following command:
> $ /sbin/mkfs -t ext3 -q disk-image
> mke2fs 1.32 (09-Nov-2002)
> disk-image is not a block special device.
> Proceed anyway? (y,n) y
> You are asked whether to proceed because this is a file, and not
> a block device. That is OK.
> Next, you need to create a directory that will serve as a mount
> point for the loopback device.
> $ mkdir fs
> You must do the next command as root, or with an account that has
> superuser privileges.
> # mount -o loop=/dev/loop0 disk-image fs
> You can now create new files, write to them, read them, and do
> everything you normally would do on a disk drive. To make normal
> user to use this filesystem you need to give valid permission to
> the directory holding this filesystem.