Sometimes it is desirable to put files into a file system, that can be mounted.
Examples are initial ram disc for the boot, preparation contents of a CD, backup of a memory device.
Here the steps:
Create a file in current directory of bs size filled with zeros (see dd)
dd if=/dev/zero of=<filename>
bs=3000k count=1
Format it as file system
mke2fs -F -m0<filename>
Mount the file as device (Note: The kernel must support loop devices)
mount -t ext2 -o loop<filename>
/mnt/<mountpoint>
Now everything can be copied there. If finished unmount it.
umount /mnt/<filename>
When it will be distributed then it is probably worth to zip it.
gzip -9<filename>
When be used on a later stage, unzip and mount it:
mount -t ext2 -o loop<filename>
/mnt/<mountpoint>