If you have NBD support enabled in your kernel, you can use this
to read a file over HTTP as a block device. The most obvious use
for me was (is) to mount ISO images without having to download
them entirely. If your linux distribution installer allows early
console access, you should be able to even install the OS from
a CD ISO over HTTP.

The homepage is http://patraulea.com/nbd-http/

To use it, compile (you need kernel headers and pthreads 
installed), load the kernel module and run nbd-http:

make
modprobe nbd
./nbd-http /dev/nbd0 http://mirror.org/file.iso

(and in another console)

mount /dev/nbd0 /mnt/cdrom

Depending on your 'net connection you might want to try different
read-ahead time limits or different thread numbers. You can change
those in the first lines of main.c. On my 512kbps cable modem, a
2..4sec read-ahead limit and 1..2 threads seem to be reasonable.

Annoyances:
-----------
Caching is done on disk. So if your fs does not support holes in
files it'll create a 2.7G file when you start serving the Fedora
Core DVD.

The reusing of HTTP connections to fetch pages of the file may
or may not be smart enough. When reading a reasonably large file
(say, larger than 4K) it should be ok.

Due to the nbd driver using the userland process to make block 
requests, there is apparently no other way to stop the nbd 
userland helper other than ``killall -9 nbd-http''.

Verbosity is set to maximum since the code is still buggy. To
get rid of most stuff, use '-v 1'. To get rid of everything 
except errors, use '-v 0'.

WARNING:
--------
Since closing useless HTTP connections and opening new ones 
occasionally happens (especially with weird (not iso9660) formats
and less-than-smart installers), you might get banned from
your favourite mirror for excessive connections. As an example,
installing Slackware 10.2 should require one connection when
determining ISO size, one when reading the directory tree and
several more when installing packages.

Think that whenever you skip a package the HTTP connection may 
become useless if when reading-ahead it doesn't reach the next 
package.


Feedback is welcome at reverse(moc.liamg@cojrah) - Harjoc Bogdan.