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Date: Fri, 2 May 2014 15:34:09 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: Rusty Russell <rusty@rustcorp.com.au>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
        Mateusz Guzik <mguzik@redhat.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
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        Borislav Petkov <bp@alien8.de>, Ingo Molnar <mingo@kernel.org>,
        Mel Gorman <mgorman@suse.de>, Kay Sievers <kay@vrfy.org>
Subject: Re: [RFC PATCH] cmdline: Hide "debug" from /proc/cmdline
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On Mon, 07 Apr 2014 14:24:45 +0930 Rusty Russell <rusty@rustcorp.com.au> wrote:

> Subject: param: hand arguments after -- straight to init
> 
> The kernel passes any args it doesn't need through to init, except it
> assumes anything containing '.' belongs to the kernel (for a module).
> This change means all users can clearly distinguish which arguments
> are for init.
> 
> For example, the kernel uses debug ("dee-bug") to mean log everything to
> the console, where systemd uses the debug from the Scandinavian "day-boog"
> meaning "fail to boot".  If a future versions uses argv[] instead of
> reading /proc/cmdline, this confusion will be avoided.
> 
> eg: test 'FOO="this is --foo"' -- 'systemd.debug="true true true"'
> 
> Gives:
> argv[0] = '/debug-init'
> argv[1] = 'test'
> argv[2] = 'systemd.debug=true true true'
> envp[0] = 'HOME=/'
> envp[1] = 'TERM=linux'
> envp[2] = 'FOO=this is --foo'

This (user-facing) feature doesn't seem to have been documented
anywhere.  Documentation/kernel-parameters.txt, I guess.