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