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- Explaining the "No working init found." boot hang message
- =========================================================
- :Authors: Andreas Mohr <andi at lisas period de>
- Cristian Souza <cristianmsbr at gmail period com>
- This document provides some high-level reasons for failure
- (listed roughly in order of execution) to load the init binary.
- 1) **Unable to mount root FS**: Set "debug" kernel parameter (in bootloader
- config file or CONFIG_CMDLINE) to get more detailed kernel messages.
- 2) **init binary doesn't exist on rootfs**: 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).
- 3) **Broken console device**: 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=``.
- 4) **Binary exists but dependencies not available**: E.g. required 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.
- 5) **Binary cannot be loaded**: 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 a 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.
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