Mounting Filesystem over existing directory

[Tito]

On Wednesday 30 May 2012 11:42:59 Eduardo Tongson wrote:
> On Wed, May 30, 2012 at 9:23 AM, ralda at gmx.de <ralda at gmx.de> wrote:
> > Hi Eduardo !
> >
> >> Yes that's possible just bind mount a tmpfs dir. So create a tmpfs
> >> somewhere eg. /tmpfs then mount -o bind /tmpfs /etc.
> >
> > This is incorrect. If you mount a file system this way you replace the
> > original contents of the directory with contents of the new file system.
> >
> > The question was to merge the contents of the two file systems. You
> > either need to fiddle with symlinks, or need to copy original content
> > to a tmpfs and mount that on /etc, or you need to use a union file
> > system (which is not part of the standard kernel).
> 
> Oops misunderstood. Sorry!

Hi,
At boot:
	mkdir -p  /var/cache/etc
	chmod 644 /var/cache/etc;
	chown root.root  /var/cache/etc;
	cp /etc/fstab /var/cache/etc/fstab
	chown root.root  /var/cache/etc/fstab;
	chmod 644  /var/cache/etc/fstab;
	mount --bind /var/cache/etc/fstab /etc/fstab;

So you you write to /etc/fstab but in reality /var/cache/etc/fstab is modified.

Just my 2 cents

Ciao,
Tito