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Diffstat (limited to 'Documentation/admin-guide/init.rst')
-rw-r--r-- | Documentation/admin-guide/init.rst | 76 |
1 files changed, 36 insertions, 40 deletions
diff --git a/Documentation/admin-guide/init.rst b/Documentation/admin-guide/init.rst index e89d97f31eaf..41f06a09152e 100644 --- a/Documentation/admin-guide/init.rst +++ b/Documentation/admin-guide/init.rst @@ -1,52 +1,48 @@ -Explaining the dreaded "No init found." boot hang message +Explaining the "No working init found." boot hang message ========================================================= +:Authors: Andreas Mohr <andi at lisas period de> + Cristian Souza <cristianmsbr at gmail period com> -OK, so you've got this pretty unintuitive message (currently located -in init/main.c) and are wondering what the H*** went wrong. -Some high-level reasons for failure (listed roughly in order of execution) -to load the init binary are: - -A) Unable to mount root FS -B) init binary doesn't exist on rootfs -C) broken console device -D) binary exists but dependencies not available -E) binary cannot be loaded - -Detailed explanations: - -A) Set "debug" kernel parameter (in bootloader config file or CONFIG_CMDLINE) - to get more detailed kernel messages. -B) 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) -C) 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). +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=``. -D) 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. -E) 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. + +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 patch to LKML. +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. +- Try to make the implementation itself more helpful in general, e.g. by + providing additional error messages at affected places. -Andreas Mohr <andi at lisas period de> |