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Splitted live-snapshot patches + some comments on snapshot internals

On Monday 09 June 2008, 02:46:53, Otavio Salvador wrote:

> > The latter ext2 is meant to ease the creation of the "Cow" persistent
> > media instead of using tmpfs which is the original casper solution for
> > persistence from ubuntu. But this way has proven to be slow in practice,
> > although is the most "unplug power cord" friendly one.

> Could you give a better explanation how this tmpfs solution used to
> work? I didn't see it and would be interesting for a whole situation
> understanding.

It is easy: aufs and unionfs needs a writable filesystem to use for "cow" 
(copy on write), the default debian-live boot mounts a tmpfs to provide that.

If "persistent" is a boot time parameter the script will try to find a file or 
a partition named (labeled) "live-rw" and if it finds it it tries to mount it 
instead of the tmpfs, so your modification will survive reboots.

This solution is expensive for a usb-key, although is fine for a mounted hd 
partition or a file image. Since it was expensive for usb using, it rose the 
needings for a faster system like my snapshot solution.

This solution should work right now, but live-snapshot could not help you in 
building the file-image at runtime since  "live/cow" is hidden 'cause of a 
mount option bug.

> > Any wishlist or ideas on snapshot/persistent topic here?
> I've been using ext3 since ext2 corrupt too easily.

ext2/ext3 are both supported now.


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