Date: Thu, 03 Dec 2015 14:15:25 -0700 From: Ian Lepore <ian@freebsd.org> To: Warner Losh <imp@bsdimp.com>, Ed Maste <emaste@freebsd.org> Cc: "freebsd-arch@freebsd.org" <freebsd-arch@freebsd.org> Subject: Re: Removing build metadata, for reproducible kernel builds Message-ID: <1449177325.6214.14.camel@freebsd.org> In-Reply-To: <CANCZdfqP3=%2BBHM_%2B=ZrNouGrXW5WAwHC87F2teEi%2BE2j-AMm6g@mail.gmail.com> References: <CAPyFy2AYeN9XNg=b0=JMWDC9ctWarfiZ-5zQorOPhguDJgxYpg@mail.gmail.com> <D9AF1C8B-431C-4359-988F-FDEEF8FAD981@bsdimp.com> <CAPyFy2CZYV%2B-5pDQjCA4Btct1VZUyEQUuL2iU1z07Ff-n2Y9Hg@mail.gmail.com> <CANCZdfqP3=%2BBHM_%2B=ZrNouGrXW5WAwHC87F2teEi%2BE2j-AMm6g@mail.gmail.com>
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On Thu, 2015-12-03 at 12:53 -0700, Warner Losh wrote: > On Thu, Dec 3, 2015 at 12:55 AM, Ed Maste <emaste@freebsd.org> wrote: > > > On 3 December 2015 at 05:51, Warner Losh <imp@bsdimp.com> wrote: > > > > > > I noted in the review that I don¢t like the default being no. > > > > > > I also don¢t like that we¢re growing lots of different knobs that need > > > to be set to get a repeatable build. Let¢s have one, or barring that, > > > let¢s have one that sets all the sub-knobs. > > > > My hope is that we'll have a reproducible build by default, and that > > *no* knobs need to be set. That's what I intend with my patch. I can > > rename the knob to WITH_/WITHOUT_REPRODUCIBLE_BUILD though if that's > > generally desired. If there's a consensus to default to including the > > metadata I'm fine with setting it in make release. > > > I think this an unwise decision in the current form suggested. The kernel > metadata has saved my butt enough times I really don't want to see it > go by default. But see below for a reasonable (imho) middle ground that > would be a good default. > I'm curious why anyone wants this enabled by default, like... are we missing something? Does it improve freebsd-update behavior maybe? If it's just for some general "reproducibility is good" philosophy then I would counter with "information is even better, so don't throw it away without a good reason." Reproducibility is good for some people, and completely useless for others, and the people who need it aren't going to mind turning on a knob or two to get what they want. > > > > I think that host and path are more worthless than date and time > > > in many environments. Who builds it likewise. Those are all things > > > that are likely to change between builds, yet change the kernel > > > image. I¢d rather see it all gone when this option is in effect. > > > > I don't follow -- other than the build iteration number (which I > > indeed missed), it is all gone. > > > > Yea I was reading things backwards. > > In the review, I suggested that if you've modified the tree (which the SCM > will tell you), then do the old format to preserve useful metadata that's > really really needed and if not to use the shorter version. When you've > modified the tree, reproducible builds aren't a concern at all. > How are you going to determine what consitutes a modified tree? What you think of as modifications may be what I call my baseline version. -- Ian
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