diff options
author | Andreas Mohr <andi@lisas.de> | 2010-03-05 16:42:39 -0500 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2010-03-06 14:26:29 -0500 |
commit | 9a85b8d6049cbb0e7961df2069322fbc4192026a (patch) | |
tree | e9e397a35ea33f198da51027db028bf91a090b4d /Documentation | |
parent | 87d5e0236d9d688fb575e9e12232764ac617617c (diff) |
init/main.c: improve usability in case of init binary failure
- new Documentation/init.txt file describing various forms of failure
trying to load the init binary after kernel bootup
- extend the init/main.c init failure message to direct to
Documentation/init.txt
Signed-off-by: Andreas Mohr <andi@lisas.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'Documentation')
-rw-r--r-- | Documentation/init.txt | 49 |
1 files changed, 49 insertions, 0 deletions
diff --git a/Documentation/init.txt b/Documentation/init.txt new file mode 100644 index 000000000000..535ad5e82b98 --- /dev/null +++ b/Documentation/init.txt | |||
@@ -0,0 +1,49 @@ | |||
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 | A) Unable to mount root FS | ||
9 | B) init binary doesn't exist on rootfs | ||
10 | C) broken console device | ||
11 | D) binary exists but dependencies not available | ||
12 | E) binary cannot be loaded | ||
13 | |||
14 | Detailed explanations: | ||
15 | 0) Set "debug" kernel parameter (in bootloader config file or CONFIG_CMDLINE) | ||
16 | to get more detailed kernel messages. | ||
17 | A) 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) | ||
22 | C) 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= . | ||
26 | D) 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. | ||
29 | E) 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 | |||
39 | Please extend this explanation whenever you find new failure causes | ||
40 | (after all loading the init binary is a CRITICAL and hard transition step | ||
41 | which needs to be made as painless as possible), then submit patch to LKML. | ||
42 | Further 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 | |||
49 | Andreas Mohr <andi at lisas period de> | ||