Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752069AbZL0PDc (ORCPT ); Sun, 27 Dec 2009 10:03:32 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751655AbZL0PDb (ORCPT ); Sun, 27 Dec 2009 10:03:31 -0500 Received: from rhlx01.hs-esslingen.de ([129.143.116.10]:34047 "EHLO rhlx01.hs-esslingen.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751130AbZL0PDa (ORCPT ); Sun, 27 Dec 2009 10:03:30 -0500 Date: Sun, 27 Dec 2009 16:03:29 +0100 From: Andreas Mohr To: Andreas Mohr Cc: Andrew Morton , Nick Bowler , linux-kernel@vger.kernel.org Subject: [PATCH] Improve usability in case of init binary failure Message-ID: <20091227150329.GA25711@rhlx01.hs-esslingen.de> References: <20091116194015.GA13820@rhlx01.hs-esslingen.de> <20091116203545.GA2028@emergent.ellipticsemi.com> <20091117204015.GB5746@rhlx01.hs-esslingen.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20091117204015.GB5746@rhlx01.hs-esslingen.de> X-Priority: none User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4070 Lines: 87 On Tue, Nov 17, 2009 at 09:40:16PM +0100, Andreas Mohr wrote: > I'll submit a new version of this patch very soon. Well, took quite a while longer, partly due to broken Broadcom USB host (OpenWrt fix to be submitted) and non-working USB-audio on nicer platforms. Took most of the comments into account (thanks!), improved some wording. Patch against current git, compile- and runtime-tested, checkpatch.pl'd (with a single nice hierarchy warning resulting from mixing git diff output and manual /dev/null diffing). Thanks! Signed-off-by: Andreas Mohr diff --git a/init/main.c b/init/main.c index dac44a9..33748c6 100644 --- a/init/main.c +++ b/init/main.c @@ -836,7 +836,8 @@ static noinline int init_post(void) run_init_process("/bin/init"); run_init_process("/bin/sh"); - panic("No init found. Try passing init= option to kernel."); + panic("No init found. Try passing init= option to kernel. " + "See Linux Documentation/init.txt for guidance."); } static int __init kernel_init(void * unused) --- /dev/null 2009-12-27 16:25:29.521258205 +0100 +++ Documentation/init.txt 2009-12-27 15:47:46.000000000 +0100 @@ -0,0 +1,49 @@ +Explaining the dreaded "No init found." boot hang message +========================================================= + +OK, so you've got this pretty unintuitive message (currently located +in init/main.c) and are wondering what the H*** went wrong. +Some high-level reasons for failure (listed roughly in order of execution) +to load the init binary are: +A) Unable to mount root FS +B) init binary doesn't exist on rootfs +C) broken console device +D) binary exists but dependencies not available +E) binary cannot be loaded + +Detailed explanations: +0) Set "debug" kernel parameter (in bootloader config file or CONFIG_CMDLINE) + to get more detailed kernel messages. +A) make sure you have the correct root FS type + (and root= kernel parameter points to the correct partition), + required drivers such as storage hardware (such as SCSI or USB!) + and filesystem (ext3, jffs2 etc.) are builtin (alternatively as modules, + to be pre-loaded by an initrd) +C) Possibly a conflict in console= setup --> initial console unavailable. + E.g. some serial consoles are unreliable due to serial IRQ issues (e.g. + missing interrupt-based configuration). + Try using a different console= device or e.g. netconsole= . +D) e.g. required library dependencies of the init binary such as + /lib/ld-linux.so.2 missing or broken. Use readelf -d |grep NEEDED + to find out which libraries are required. +E) make sure the binary's architecture matches your hardware. + E.g. i386 vs. x86_64 mismatch, or trying to load x86 on ARM hardware. + In case you tried loading a non-binary file here (shell script?), + you should make sure that the script specifies an interpreter in its shebang + header line (#!/...) that is fully working (including its library + dependencies). And before tackling scripts, better first test a simple + non-script binary such as /bin/sh and confirm its successful execution. + To find out more, add code to init/main.c to display kernel_execve()s + return values. + +Please extend this explanation whenever you find new failure causes +(after all loading the init binary is a CRITICAL and hard transition step +which needs to be made as painless as possible), then submit patch to LKML. +Further TODOs: +- Implement the various run_init_process() invocations via a struct array + which can then store the kernel_execve() result value and on failure + log it all by iterating over _all_ results (very important usability fix). +- try to make the implementation itself more helpful in general, + e.g. by providing additional error messages at affected places. + +Andreas Mohr -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/