Re: unionfs

From: Claudio Martins
Date: Mon Mar 15 2004 - 12:10:31 EST



On Monday 15 March 2004 16:13, Jörn Engel wrote:
> On Mon, 15 March 2004 22:35:20 +0800, Ian Kent wrote:
> > I don't understand the requirement properly. Sorry.
>
> Depends on who you ask, but imo it boils down to this:
> - Use one filesystem as backing store, usually ro.
> - Have another filesystem on top for extra functionality, usually rw
> access.
>
> Famous example is a rw-CDROM, where writes go to hard drive and
> unchanged data is read from CDROM. But it makes sense for other
> things as well.


If I understand correctly this unionfs feature would also be the cleanest
way of changing the root filesystem after using an initrd ramdisk on boot.
Currently the pivot_root call is used to change root but that still implies a
bit of a hack. You can read about it on this fine paper:

http://www.cis.udel.edu/~zhi/www.docshow.net/linux/ols.zip


It's also a good read if you want to understand the linux bootloaders and
the boot process in general.

Regards

Claudio

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