0001 Explaining the "No working init found." boot hang message
0002 =========================================================
0003 :Authors: Andreas Mohr <andi at lisas period de>
0004 Cristian Souza <cristianmsbr at gmail period com>
0005
0006 This document provides some high-level reasons for failure
0007 (listed roughly in order of execution) to load the init binary.
0008
0009 1) **Unable to mount root FS**: Set "debug" kernel parameter (in bootloader
0010 config file or CONFIG_CMDLINE) to get more detailed kernel messages.
0011
0012 2) **init binary doesn't exist on rootfs**: Make sure you have the correct
0013 root FS type (and ``root=`` kernel parameter points to the correct
0014 partition), required drivers such as storage hardware (such as SCSI or
0015 USB!) and filesystem (ext3, jffs2, etc.) are builtin (alternatively as
0016 modules, to be pre-loaded by an initrd).
0017
0018 3) **Broken console device**: Possibly a conflict in ``console= setup``
0019 --> initial console unavailable. E.g. some serial consoles are unreliable
0020 due to serial IRQ issues (e.g. missing interrupt-based configuration).
0021 Try using a different ``console= device`` or e.g. ``netconsole=``.
0022
0023 4) **Binary exists but dependencies not available**: E.g. required library
0024 dependencies of the init binary such as ``/lib/ld-linux.so.2`` missing or
0025 broken. Use ``readelf -d <INIT>|grep NEEDED`` to find out which libraries
0026 are required.
0027
0028 5) **Binary cannot be loaded**: Make sure the binary's architecture matches
0029 your hardware. E.g. i386 vs. x86_64 mismatch, or trying to load x86 on ARM
0030 hardware. In case you tried loading a non-binary file here (shell script?),
0031 you should make sure that the script specifies an interpreter in its
0032 shebang header line (``#!/...``) that is fully working (including its
0033 library dependencies). And before tackling scripts, better first test a
0034 simple non-script binary such as ``/bin/sh`` and confirm its successful
0035 execution. To find out more, add code ``to init/main.c`` to display
0036 kernel_execve()s return values.
0037
0038 Please extend this explanation whenever you find new failure causes
0039 (after all loading the init binary is a CRITICAL and hard transition step
0040 which needs to be made as painless as possible), then submit a patch to LKML.
0041 Further TODOs:
0042
0043 - Implement the various ``run_init_process()`` invocations via a struct array
0044 which can then store the ``kernel_execve()`` result value and on failure
0045 log it all by iterating over **all** results (very important usability fix).
0046 - Try to make the implementation itself more helpful in general, e.g. by
0047 providing additional error messages at affected places.
0048
