[CLUE-Tech] Cool CD trick

[Jed S. Baer]

Leaping gleafully about, and grinning madly,
Grant Johnson <grant at amadensor.com> wrote:

> I just found a COOL trick for using ISO's.  You can mount them, without 
> ever even buring them, as long as you have loopback file support in you 
> kernel.
> 
> OK, now......  How do I make an ISO from a bunch of files?   How about 
> ripping one from a data CD?  So many cool things to play with....

You can do all manner of things using the loopback device.

How about an encrypted ext2 filesystem? Create a big contiguous file,
using dd, mkext2fs on it, mount it using the loopback device, put your
private data on it, dismount, and then encrypt it. Yeah, that's the clunky
version. Dunno what the non-clunky approach is, that's just off the top of
my head.

Good info on the basics of using a chunk-o-disk and the loopback device is
in the CD-Writing HOWTO. Obviously not restricted to burning CDs.

Another use, perhaps silly, is to use it to enforce user quotas, without
having quotas. Want the PHB to have only 20MB? ;-) Don't carve up your
existing partition, just give him/her that much in a container file, and
mount it using the loopback device.

The "container file" for the filesystem is also easy to backup using tar,
so at that point you have a (forget the term for it) "export" of it. Fer
that matter, "exporting" the filesystem to backup media is as easy as
copying it.

jed
-- 
"Those who expect to reap the blessings of freedom must, like men,
 undergo the fatigue of supporting it."
 - Thomas Paine