| 1 | Explaining the "No working init found." boot hang message
|
| 2 | =========================================================
|
| 3 | :Authors: Andreas Mohr <andi at lisas period de>
|
| 4 | Cristian Souza <cristianmsbr at gmail period com>
|
| 5 |
|
| 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).
|
| 21 | Try using a different ``console= device`` or e.g. ``netconsole=``.
|
| 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.
|
| 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
|
| 40 | which needs to be made as painless as possible), then submit a patch to LKML.
|
| 41 | Further TODOs:
|
| 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).
|
| 46 | - Try to make the implementation itself more helpful in general, e.g. by
|
| 47 | providing additional error messages at affected places.
|
| 48 |
|