differential filesystems? (was Re: [plug] Compressed filesystems)

[Russell Steicke]

On Wed, Apr 17, 2002 at 06:15:12PM +0800, Bernard Blackham wrote:
> On a related topic, has anybody seen or heard of a filesystem that
> will load off a read-only device, such as a CD-ROM, but store all
> changes in memory? Obviously, it wouldn't have a very long

OpenBSD (and probably the other BSDs, too) has union filesystems, but
it's not in memory, it's on two merged partitions.

User mode linux can use COW (copy on write) filesystems, where you have
a filesystem in a file on the host, with another file on the host to
which the changes are written.  If the thing gets corrupted you stop the
virtual machine, kill the cow (virtual steak??), and start again clean.
You can also merge the cow into the base fs if you are happy with the
changes, and use a single base fs with multiple user mode linux images,
each with its own cow.  Very cool.

  http://user-mode-linux.sf.net/

These don't actually do what you were after, but are interesting in
their own right, and may be a starting point if you need to roll your
own.


> Bernard.


-- 
Russell Steicke

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