[lug] RAM based files, file systems

[Hugh Brown]

On Tue, 2004-01-27 at 23:31, D. Stimits wrote:
> Steve Sullivan wrote:
> 
> > Is it possible to create files, or file systems,
> > that exist only in RAM?  Long ago Solaris supported
> > such a feature, but I don't find it in Linux.
> >
> > Kind of like /proc, but where users can write small temp files
> > for better performance.
> 
> Just use the loopback device. If you check up on how to view an iso9660 
> file (not cd rom), such as created with mkisofs, then you also know how 
> to create and make filesystems with virtually any filesystem type in 
> ram. Whether something might get swapped out is another story. In 
> essense a loopback device can be made to look like any filesystem type, 
> and formatted, written, read, and mounted/umounted.
> 
> D. Stimits, stimits AT comcast DOT net
> 
> 

is it really done in ram or is it done in a file?  e.g. I assume I can
use dd to create a 512MB file, mount it via the loopback device and then
format it.  When I write to the loopback mounted file, aren't I making
changes to the original file on disk? 

Here's the counter-example to my question:

I know knoppix does something related to this.  There's an iso image
that is cramfs'ified and then mounted via the loopback.  I'm just not
sure how it does the whole in memory only thing (obviously you can't
write to a cdr which is where the crammed iso image lives).

So how does the in RAM fs work (it's obvious that knoppix is exceeding
the 4k limit on a ramdisk)?

Hugh





> _______________________________________________
> Web Page:  http://lug.boulder.co.us
> Mailing List: http://lists.lug.boulder.co.us/mailman/listinfo/lug
> Join us on IRC: lug.boulder.co.us port=6667 channel=#colug
>