Commit 9a85b8d6049cbb0e7961df2069322fbc4192026a
Committed by
Linus Torvalds
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87d5e0236d
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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>
Showing 2 changed files with 51 additions and 1 deletions Side-by-side Diff
Documentation/init.txt
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> |
init/main.c
... | ... | @@ -847,7 +847,8 @@ |
847 | 847 | run_init_process("/bin/init"); |
848 | 848 | run_init_process("/bin/sh"); |
849 | 849 | |
850 | - panic("No init found. Try passing init= option to kernel."); | |
850 | + panic("No init found. Try passing init= option to kernel. " | |
851 | + "See Linux Documentation/init.txt for guidance."); | |
851 | 852 | } |
852 | 853 | |
853 | 854 | static int __init kernel_init(void * unused) |