Mounting Filesystem over existing directory

[Bartos-Elekes Zsolt]

Sameer Naik wrote:

 > Consider that i have a readonly filesystem mounted at / and that the
 > /etc folder consists of some files. Is is possible to mount a ramfs
 > filesystem at /etc such that the existing files in the /etc partition
 > are still accessible and any new files written to the /etc partition
 > are saved in the ramfs (which will be lost upon reboot).

Yes, you need unionfs or aufs.

http://www.filesystems.org/project-unionfs.html
http://aufs.sourceforge.net/aufs.html

-- 
Zsolt