Hello Mr. Okajima! :) Thank you for letting me know that it is not possible to use aufs as a branch. This means I need to do my task differently.
Slax has this setup / (root) = tmpfs (rw) + ro1 + ro2 + ro3 ... Now I realized that for my purposes I actually do not need to reuse the tmpfs branch. So in fact I do not need my current root (aufs) as a branch, I can simply setup another union mount from scratch, with my existing ro branches and a new (empty) tmpfs, like this: /another_union = tmpfs2 (different) + ro1 + ro2 + ro3 ... and I will chroot this, it will be probably even better for my purposes. By the way, I am very happy that Debian has aufs patches in their stock kernel, so adding AUFS to debian is a matter of single command (apt install aufs-dkms) without the need to recompile kernel. This makes life so easier :) Happy 2018! :-) Tomas M On Thu, Dec 28, 2017 at 5:49 PM, <sf...@users.sourceforge.net> wrote: > Hi Tomas, > Glad to hear from you again. > > Tomas M: >> can I use aufs mount as a branch of another aufs mount? > > Basically, you can't. > Technically, such hierarchy will cause an internal recursive call which > consumes the stack space a lot. Aufs explicitly prohibited it in the > beginning. Later, another user had requested me to support it, and I did > after some investigation and consideration. It was implemented with > CONFIG_AUFS_ROBR "Aufs as an readonly branch of another aufs mount" in > aufs1-age. But the feature was un-popular and I removed it when aufs has > grown up. > > Current linux kernel consumes the less stack space than it used > to. Additinonally the small stack space (4KB) configuration is gone > now. So I guess it should be enough possible now. But it is suspicious > for me to think it is really necessary. > > >> Is there any workaround? >> My goal is to create a chroot which will have current root as a >> readonly branch, and tmpfs as writable branch. > > Why don't you try stacking onto a single aufs mount? > - /(root) = /rwA + /roB > - /union = /changes > - /union(new) = /changes + /rwA + /roB > instead of > /union(new) = /changes + /root > > > J. R. Okajima ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot
