About Kernel Documentation Linux Kernel Contact Linux Resources Linux Blog

Documentation / admin-guide / init.rst




Custom Search

Based on kernel version 4.16.1. Page generated on 2018-04-09 11:52 EST.

1	Explaining the dreaded "No init found." boot hang message
2	=========================================================
3	
4	OK, so you've got this pretty unintuitive message (currently located
5	in init/main.c) and are wondering what the H*** went wrong.
6	Some high-level reasons for failure (listed roughly in order of execution)
7	to load the init binary are:
8	
9	A) Unable to mount root FS
10	B) init binary doesn't exist on rootfs
11	C) broken console device
12	D) binary exists but dependencies not available
13	E) binary cannot be loaded
14	
15	Detailed explanations:
16	
17	A) Set "debug" kernel parameter (in bootloader config file or CONFIG_CMDLINE)
18	   to get more detailed kernel messages.
19	B) make sure you have the correct root FS type
20	   (and ``root=`` kernel parameter points to the correct partition),
21	   required drivers such as storage hardware (such as SCSI or USB!)
22	   and filesystem (ext3, jffs2 etc.) are builtin (alternatively as modules,
23	   to be pre-loaded by an initrd)
24	C) Possibly a conflict in ``console= setup`` --> initial console unavailable.
25	   E.g. some serial consoles are unreliable due to serial IRQ issues (e.g.
26	   missing interrupt-based configuration).
27	   Try using a different ``console= device`` or e.g. ``netconsole=``.
28	D) e.g. required library dependencies of the init binary such as
29	   ``/lib/ld-linux.so.2`` missing or broken. Use
30	   ``readelf -d <INIT>|grep NEEDED`` to find out which libraries are required.
31	E) make sure the binary's architecture matches your hardware.
32	   E.g. i386 vs. x86_64 mismatch, or trying to load x86 on ARM hardware.
33	   In case you tried loading a non-binary file here (shell script?),
34	   you should make sure that the script specifies an interpreter in its shebang
35	   header line (``#!/...``) that is fully working (including its library
36	   dependencies). And before tackling scripts, better first test a simple
37	   non-script binary such as ``/bin/sh`` and confirm its successful execution.
38	   To find out more, add code ``to init/main.c`` to display kernel_execve()s
39	   return values.
40	
41	Please extend this explanation whenever you find new failure causes
42	(after all loading the init binary is a CRITICAL and hard transition step
43	which needs to be made as painless as possible), then submit patch to LKML.
44	Further TODOs:
45	
46	- Implement the various ``run_init_process()`` invocations via a struct array
47	  which can then store the ``kernel_execve()`` result value and on failure
48	  log it all by iterating over **all** results (very important usability fix).
49	- try to make the implementation itself more helpful in general,
50	  e.g. by providing additional error messages at affected places.
51	
52	Andreas Mohr <andi at lisas period de>
Hide Line Numbers
About Kernel Documentation Linux Kernel Contact Linux Resources Linux Blog

Information is copyright its respective author. All material is available from the Linux Kernel Source distributed under a GPL License. This page is provided as a free service by mjmwired.net.