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7dbffd3f | 1 | Explaining the "No working init found." boot hang message |
9a85b8d6 | 2 | ========================================================= |
7dbffd3f CS |
3 | :Authors: Andreas Mohr <andi at lisas period de> |
4 | Cristian Souza <cristianmsbr at gmail period com> | |
9a85b8d6 | 5 | |
7dbffd3f CS |
6 | This document provides some high-level reasons for failure |
7 | (listed roughly in order of execution) to load the init binary. | |
8 | ||
9 | 1) **Unable to mount root FS**: Set "debug" kernel parameter (in bootloader | |
10 | config file or CONFIG_CMDLINE) to get more detailed kernel messages. | |
11 | ||
12 | 2) **init binary doesn't exist on rootfs**: Make sure you have the correct | |
13 | root FS type (and ``root=`` kernel parameter points to the correct | |
14 | partition), required drivers such as storage hardware (such as SCSI or | |
15 | USB!) and filesystem (ext3, jffs2, etc.) are builtin (alternatively as | |
16 | modules, to be pre-loaded by an initrd). | |
17 | ||
18 | 3) **Broken console device**: Possibly a conflict in ``console= setup`` | |
19 | --> initial console unavailable. E.g. some serial consoles are unreliable | |
20 | due to serial IRQ issues (e.g. missing interrupt-based configuration). | |
8887adde | 21 | Try using a different ``console= device`` or e.g. ``netconsole=``. |
7dbffd3f CS |
22 | |
23 | 4) **Binary exists but dependencies not available**: E.g. required library | |
24 | dependencies of the init binary such as ``/lib/ld-linux.so.2`` missing or | |
25 | broken. Use ``readelf -d <INIT>|grep NEEDED`` to find out which libraries | |
26 | are required. | |
27 | ||
28 | 5) **Binary cannot be loaded**: Make sure the binary's architecture matches | |
29 | your hardware. E.g. i386 vs. x86_64 mismatch, or trying to load x86 on ARM | |
30 | hardware. In case you tried loading a non-binary file here (shell script?), | |
31 | you should make sure that the script specifies an interpreter in its | |
32 | shebang header line (``#!/...``) that is fully working (including its | |
33 | library dependencies). And before tackling scripts, better first test a | |
34 | simple non-script binary such as ``/bin/sh`` and confirm its successful | |
35 | execution. To find out more, add code ``to init/main.c`` to display | |
36 | kernel_execve()s return values. | |
9a85b8d6 AM |
37 | |
38 | Please extend this explanation whenever you find new failure causes | |
39 | (after all loading the init binary is a CRITICAL and hard transition step | |
7dbffd3f | 40 | which needs to be made as painless as possible), then submit a patch to LKML. |
9a85b8d6 | 41 | Further TODOs: |
8887adde MCC |
42 | |
43 | - Implement the various ``run_init_process()`` invocations via a struct array | |
44 | which can then store the ``kernel_execve()`` result value and on failure | |
45 | log it all by iterating over **all** results (very important usability fix). | |
7dbffd3f CS |
46 | - Try to make the implementation itself more helpful in general, e.g. by |
47 | providing additional error messages at affected places. | |
9a85b8d6 | 48 |