linux-kernel - Re: [PATCH v1] docs: describe how to quickly build Linux

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Date:   Wed, 1 Feb 2023 15:02:15 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Thorsten Leemhuis <linux@...mhuis.info>
Cc:     Jonathan Corbet <corbet@....net>,
        Randy Dunlap <rdunlap@...radead.org>,
        Lukas Bulwahn <lukas.bulwahn@...il.com>,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        regressions@...ts.linux.dev
Subject: Re: [PATCH v1] docs: describe how to quickly build Linux

On Wed, Feb 01, 2023 at 02:22:07PM +0100, Thorsten Leemhuis wrote:
> On 01.02.23 13:44, Greg KH wrote:
> > On Wed, Feb 01, 2023 at 01:42:29PM +0100, Greg KH wrote:
> >> On Wed, Feb 01, 2023 at 12:52:30PM +0100, Thorsten Leemhuis wrote:
> >>> Add a text explaining how to quickly build a kernel, as that's something
> >>> users will often have to do when they want to report an issue or test
> >>> proposed fixes. This is a huge and frightening task for quite a few
> >>> users these days, as many rely on pre-compiled kernels and have never
> >>> built their own. They find help on quite a few websites explaining the
> >>> process in various ways, but those howtos often omit important details
> >>> or make things too hard for the 'quickly build just for testing' case
> >>> that 'localmodconfig' is really useful for. Hence give users something
> >>> at hand to guide them, as that makes it easier for them to help with
> >>> testing, debugging, and fixing the kernel.
> >>
> >> First off, this is great, thanks for doing this.
> 
> Thx, feels good to hear.
> 
> Bisection is next on my todo list once this matured...
> 
> >> One minor comment, to prevent people from "overloading" the
> >> git.kernel.org systems:
> >>
> >>> +.. _sources_sbs:
> >>> +
> >>> + * Retrieve the sources of the Linux version you intend to build; then change
> >>> +   into the directory holding them, as all further commands in this guide are
> >>> +   meant to be executed from there.
> >>> +
> >>> +   If you plan to only build one particular kernel version, download its source
> >>> +   archive from https://kernel.org; afterwards extract its content to '~/linux/'
> >>> +   and change into the directory created during extraction.
> >>> +
> >>> +   In most other situations your best choice is to fetch the sources using git::
> >>> +
> >>> +          git clone https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git \
> >>> +            ~/linux/sources
> >>> +          cd ~/linux/sources/
> >>
> >> Ideally you should never do a "full clone from scratch" like this, as it
> >> takes up loads of server resources.  The "best" way to do this is to
> >> download the kernel git bundle, and then pull and resolve the remaining
> >> bits.  It's explained, with a script to do the work for you, here:
> >>
> >> 	https://kernel.org/best-way-to-do-linux-clones-for-your-ci.html
> > 
> > Oops, here's the full steps involved:
> > 	https://www.kernel.org/cloning-linux-from-a-bundle.html
> > the first link above has a script that does it all for you, but you
> > probably just want to copy the steps at this last link instead.
> 
> Great idea, thx for bringing this up -- now that you mention it, I
> remember those pages and the script again... :-/
> 
> Sadly my "after cloning Linus tree, add the stable tree as remote and
> fetch everything" approach would will still create a lot of load.

Not really, nothing like doing a "full" clone of the original repo.
It's a much smaller working set that needs to be handled that way on the
server side.

I do this (as do many others) for CI systems, and the primary workload
is on the client resolving the bundle, that can take a bit of time, but
that's all client side, not server.

> I
> could use the script with the stable git repo, as that includes
> mainline; but I noticed it sometimes is not fully up2date. At least I
> once noticed it was quite a few hours (or maybe even a day?) behind. Is
> that normal? I assume you should know.

I think it's generated daily, so yes, it will be a bit out of date, but
that's fine.

> Anyway: maybe "a little bit behind" isn't something that's much of a
> problem for this document.

Adding the remote and doing a pull is good and recommended, so it's fine
if it's a day or so out of date.

thanks,

greg k-h