From mboxrd@z Thu Jan 1 00:00:00 1970 From: "J. R. Okajima" Subject: Re: [PATCH 6/6] overlay: overlay filesystem documentation Date: Tue, 19 Apr 2011 12:05:17 +0900 Message-ID: <7795.1303182317@jrobl> References: <1303142440-26328-1-git-send-email-miklos@szeredi.hu> <1303142440-26328-7-git-send-email-miklos@szeredi.hu> Cc: viro@ZenIV.linux.org.uk, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, apw@canonical.com, nbd@openwrt.org, neilb@suse.de, hramrach@centrum.cz, Miklos Szeredi To: Miklos Szeredi Return-path: In-Reply-To: <1303142440-26328-7-git-send-email-miklos@szeredi.hu> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org Hello Miklos, Miklos Szeredi: > +The lower filesystem can be any filesystem supported by Linux and does > +not need to be writable. The lower filesystem can even be another > +overlayfs. ... When user mounts overlayfs over and over like this, # mount -t overlayfs -o upper=/rw1,lower=/ro1 none /ovl1 # mount -t overlayfs -o upper=/rw2,lower=/ovl1 none /ovl2 ::: # mount -t overlayfs -o upper=/rwN,lower=/ovl{N-1} none /ovlN And if he modify a file in the bottom RO layer, then overlayfs copies-up the file into each RW layer? - 'fileA' exists in only /ro1. - nested mounts. - run "echo append >> /ovlN/fileA" - is fileA copied-up to /rw1, and then to /rw2, and then ... to /rwN? If user specify a single dir as every upper laery, then the copyup will be done only once, or such RW layers are not allowed? J. R. Okajima