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Date:	Sun, 8 Nov 2009 13:00:08 +0100
From:	Andreas Mohr <andi@...as.de>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	"Michael A. Griffith" <grif@....org>, linux-kernel@...r.kernel.org
Subject: [PATCH] Please get this committed, _NOW_ (preferrably 5 years
	ago), thanks.

Hi guys,

boy am I angry about this...

When trying to get my ASUS WL-500gP v2 to boot (via the very nice
OpenWrt infrastructure) from external media for a Debian-MIPSEL
installation on it
(see e.g. http://wpkg.org/Running_Debian_on_ASUS_WL-500G_deluxe ),
I was hitting the dreaded "No init found." boot message.

5 years (FIVE G*DDARN YEARS!! Leaving me wondering what Linux development
has been doing all the time...) earlier I was in a diploma thesis project
where I had the exact same issue, with the _exact same_ error message,
which managed to waste the _exact same_ 2 or 3 hours that I managed to waste
this time again (obviously my memory is not stellar enough to be able to
recall that it was a console issue).
I needed to search through a couple dozen forum threads (with many
thread participants being helpless) to finally nail the issue I was having
this time.

Needless to say this error message is totally and deadly precisely
UNHELPFUL, proof:
Google "No init found." linux: 160000 results.
Very conservative estimate: 5000 developers times 2 hours = 10000 hours
of wasted precious developer time. An estimated lowly $50 per developer hour,
thus a grand total of $500000 (FIVE HUNDRED THOUSAND AMERICAN DOLLARS, however
broken the dollar might be at any moment in time ;) wasted
on this unhelpfully implemented yet very critical (failure will leave you
hanging dry in a hard place, with no immediate tools for remedy, with
further unsuccessful image rebuilds taking > 30 minutes each)
transition step.


IMHO as catastrophic a failure in usability as it can ever get.


Note that this patch hasn't even been compiled yet (the
"See Linux " __FILE__ " for guidance." part might be the only thing to croak).
I just wanted to get this out the door ASAP despite a tight time frame.
You'll figure it out anyway ;)

Useful ChangeLog phrase: provide crucial explanations for the dreaded
"No init found." boot failure.

Thanks,

Signed-off-by: Andreas Mohr <andi@...as.de>


--- linux-2.6.32-rc6/init/main.c.orig	2009-11-08 11:09:51.000000000 +0100
+++ linux-2.6.32-rc6/init/main.c	2009-11-08 12:40:11.000000000 +0100
@@ -846,7 +846,47 @@ 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 " __FILE__ " for guidance.");
+/* ok, so you've got this pretty unintuitive message 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) other requirements not met
+ * D) binary exists but dependencies not available
+ * E) binary cannot be loaded
+ *
+ * Detailed explanations:
+ * A) Please make sure you have the correct root FS type
+ * (and root= in bootloader or CONFIG_CMDLINE 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 by
+ * using initrd)
+ * C) Possibly a conflict in console= setup --> initial console unavailable.
+ * E.g. some serial consoles are unreliable due to serial IRQ issues.
+ * Try using a different console= device or e.g. netconsole=.
+ * D) e.g. crucial library dependencies of the init binary such as
+ * /lib/ld-linux.so.2 missing or broken. Use readelf -d <INIT>|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.
+ * Or did you try loading a non-binary file here!?! (shell script?)
+ * To find out more, add patch here 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 <andi at lisas period de>
+ */
 }
 
 static int __init kernel_init(void * unused)
--
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