[buildd-tools-devel] Bug#710073: Bug#710073: Bug#710073: sbuild: add copy-on-write support

[Geoffrey Thomas]

On Fri, 5 Jul 2013, Roger Leigh wrote:

> I would suspect that we can make it use overlayfs using the same 
> infrastructure--it'll just need teaching about the new filesystem type.

Hasn't overlayfs support been in schroot since 1.5.2-1 (May 2012)? I don't 
think any more support is needed on the sbuild side. Ubuntu seems to be 
making active use of overlayfs chroots -- mk-sbuild from ubuntu-dev-tools 
0.136 (November 2011) onwards makes them, and they carry no patches to 
schroot and no relevant patches to sbuild.

All you need a kernel with overlayfs support. Ubuntu's been carrying the 
patchset out of tree for a while.

(I was pretty sure I'd _used_ overlayfs chroots, so I was surprised by the 
implication that it doesn't work yet...)


By the way, regarding cowdancer and LD_PRELOAD, I semi-recently learned 
about fakeroot-ng, which implements fakeroot using ptrace instead of 
LD_PRELOAD and is therefore more reliable. I wonder if the same approach 
could be applied to cowdancer. (I've long wanted a "fakeschroot" that 
doesn't require elevated privilege in order to build things....)

-- 
Geoffrey Thomas
http://ldpreload.com
geofft at ldpreload.com