Bug#710073: [buildd-tools-devel] Bug#710073: Bug#710073: sbuild: add copy-on-write support
Roger Leigh writes: > On Fri, Jul 05, 2013 at 10:15:07AM -0700, Geoffrey Thomas wrote: >> 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. Might be nice if the "type=" description in schroot.conf referenced the "filesystem union chroot" options section as applying to "directory" chroots? They sound rather unappealing compared to the snapshot options there. >> 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) > > If such a thing is possible, that would be very interesting. I > don't think I'll have time to look at it myself in the near > future, but I'd certainly support any work on it. Removing all > need for root privileges for sbuild would be a great achievement; > I'd certainly be happy to remove the need for root in the build > chroot. Using ptrace() has one important drawback: there can be only one ptracer of any given process. This would make it tricky to allow using more than one such tool at a time: for this to work, either the tools would all need to be in league, or the outer tools would all have to emulate ptrace() in addition to fulfilling their actual purposes. I suppose it's a bit of work to make LD_PRELOAD-based tools play nicely others that override the same symbols, but emulating ptrace() using ptrace() is not my idea of a good time. (Also, I can't help but wonder about the performance cost of having TWO ptrace stops for *every* syscall in *every* inferior process, and it just gets worse with the ptrace() emulation ...) Also note that some packages, like gdb for example, have rather good reason to use ptrace() themselves during the build. (Say, running the testsuite.) -- Hi! I'm a .signature virus! Copy me into your ~/.signature to help me spread! -- To UNSUBSCRIBE, email to debian-bugs-dist-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org
Bug#710073: [buildd-tools-devel] Bug#710073: Bug#710073: sbuild: add copy-on-write support
On Fri, Jul 05, 2013 at 10:15:07AM -0700, Geoffrey Thomas wrote: > 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. Yes, you're correct, I'd forgotten it was already added--it's not a feature I use myself very often. > 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) If such a thing is possible, that would be very interesting. I don't think I'll have time to look at it myself in the near future, but I'd certainly support any work on it. Removing all need for root privileges for sbuild would be a great achievement; I'd certainly be happy to remove the need for root in the build chroot. Regards, Roger -- .''`. Roger Leigh : :' : Debian GNU/Linuxhttp://people.debian.org/~rleigh/ `. `' schroot and sbuild http://alioth.debian.org/projects/buildd-tools `-GPG Public Key F33D 281D 470A B443 6756 147C 07B3 C8BC 4083 E800 -- To UNSUBSCRIBE, email to debian-bugs-dist-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org
Bug#710073: [buildd-tools-devel] Bug#710073: Bug#710073: sbuild: add copy-on-write support
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 geo...@ldpreload.com -- To UNSUBSCRIBE, email to debian-bugs-dist-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org
