linux-kernel - Re: [PATCH v2] kbuild: use hostname -s along uname to obtain LINUX_COMPILE

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Date:   Fri, 1 Apr 2022 10:21:05 -0700
From:   Nathan Chancellor <nathan@...nel.org>
To:     FraSharp <f.duca00@...il.com>
Cc:     FraSharp <s23265@...ve.it>, Masahiro Yamada <masahiroy@...nel.org>,
        Michal Marek <michal.lkml@...kovi.net>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] kbuild: use hostname -s along uname to obtain
 LINUX_COMPILE_HOST

Hi Francesco,

On Fri, Apr 01, 2022 at 05:17:06PM +0200, FraSharp wrote:
> * On some systems (e.g. macOS, Debian, Fedora), using commands like 'uname -n' or
>   'hostname' will print something similar to "hostname.domain"
>   ("Francescos-Air.fritz.box" for example), which is very annoying.
>   What works instead is 'hostname -s', which will only write hostname
>   without the domain ("Francescos-Air" for example),
>   but also keep 'uname -n', as some systems as Arch Linux does not have
>   'hostname' as command.
> 
> * This commit is complementary to
>   1e66d50ad3a1dbf0169b14d502be59a4b1213149
>   ("kbuild: Use uname for LINUX_COMPILE_HOST detection")
> 
> Signed-off-by: Francesco Duca <s23265@...ve.it>
> ---
>  scripts/mkcompile_h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/scripts/mkcompile_h b/scripts/mkcompile_h
> index ca40a5258..3eefbafe5 100755
> --- a/scripts/mkcompile_h
> +++ b/scripts/mkcompile_h
> @@ -34,7 +34,7 @@ else
>  	LINUX_COMPILE_BY=$KBUILD_BUILD_USER
>  fi
>  if test -z "$KBUILD_BUILD_HOST"; then
> -	LINUX_COMPILE_HOST=`uname -n`
> +	LINUX_COMPILE_HOST=$(hostname -s 2>/dev/null || uname -n)
>  else
>  	LINUX_COMPILE_HOST=$KBUILD_BUILD_HOST
>  fi
> -- 
> 2.32.0 (Apple Git-132)
> 

I personally think this is going to output something objectively worse
for my use case. I use containers for my main workflow, which have a
hostname of "container name" and domain name of "host's hostname".

For example:

$ uname -n
thelio-3990X

$ distrobox enter dev-arch

$ uname -n
dev-arch.thelio-3990X

With the move to 'hostname -s' by default, I lose the information about
the main host machine, so I am unable to tell exactly which container
built the image:

$ hostname -s
dev-arch

While moving to containers is supposed to help eliminate the need to
know about a particular machine because it should be the same
environment, it is still relevant because I build certain tools on some
machines and not others and I am not necessarily updating each container
on the same timeline, so it is still useful to have this information
included in the kernel image for tracking purposes.

Given this is a purely a subjective/cosmetic issue, why can you not just
add something like

export KBUILD_BUILD_HOST=$(hostname -s)

in your shell's start up file, so that the hostname is in the format
that you desire?

Cheers,
Nathan