From 622985ef4ba0ef7a7e9c1b12cc8528c3c9c23897 Mon Sep 17 00:00:00 2001 From: Andreas Mohr Date: Fri, 5 Mar 2010 13:42:39 -0800 Subject: [PATCH] --- yaml --- r: 186235 b: refs/heads/master c: 9a85b8d6049cbb0e7961df2069322fbc4192026a h: refs/heads/master i: 186233: cfa0be995c9b0a68223bc501f86056f5b12786ea 186231: fe79d68fd4a1b2a02224fee5263577765b9aaf6b v: v3 --- [refs] | 2 +- trunk/Documentation/init.txt | 49 ++++++++++++++++++++++++++++++++++++ trunk/init/main.c | 3 ++- 3 files changed, 52 insertions(+), 2 deletions(-) create mode 100644 trunk/Documentation/init.txt diff --git a/[refs] b/[refs] index e3375d71ef91..1d70e431a4c1 100644 --- a/[refs] +++ b/[refs] @@ -1,2 +1,2 @@ --- -refs/heads/master: 87d5e0236d9d688fb575e9e12232764ac617617c +refs/heads/master: 9a85b8d6049cbb0e7961df2069322fbc4192026a diff --git a/trunk/Documentation/init.txt b/trunk/Documentation/init.txt new file mode 100644 index 000000000000..535ad5e82b98 --- /dev/null +++ b/trunk/Documentation/init.txt @@ -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 diff --git a/trunk/init/main.c b/trunk/init/main.c index 41d0f10dbbc7..b09a828f38b5 100644 --- a/trunk/init/main.c +++ b/trunk/init/main.c @@ -847,7 +847,8 @@ 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)