[Gllug] Loopback mountable image file compression.

[Richard Jones]

On Tue, Sep 01, 2009 at 03:43:29PM +0100, James Courtier-Dutton wrote:
> 2009/8/26 Phillip Lougher <phillip.lougher at gmail.com>:
> >
> > 3. Sparse block handling.  Squashfs detects holes (zero filled ranges)
> > and handles them specially.  Cloop compresses zero filled blocks,
> > leading to worse performance and compression.  Filesystem images often
> > have very large ranges of zero filled blocks (unused blocks).
> 
> Is there a tool to go through an ext3 partition and fill the unused
> space with zero fill?

zerofree

> Can this be done after the ext3 image has been squashfs, thus
> resulting in a smaller squashfs image?

No, but you could run zerofree on the ext3 image and then compress it.

> I can't rember is squashfs was read/write or read only.

Read-only AFAIK.  You have to prepare the squashfs images using the
mksquashfs tool (q.v.)

Rich.

-- 
Richard Jones
Red Hat
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