hc
2024-12-19 9370bb92b2d16684ee45cf24e879c93c509162da
kernel/Documentation/admin-guide/init.rst
....@@ -1,52 +1,48 @@
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-Explaining the dreaded "No init found." boot hang message
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+Explaining the "No working init found." boot hang message
22 =========================================================
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+:Authors: Andreas Mohr <andi at lisas period de>
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+ Cristian Souza <cristianmsbr at gmail period com>
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-OK, so you've got this pretty unintuitive message (currently located
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-in init/main.c) and are wondering what the H*** went wrong.
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-Some high-level reasons for failure (listed roughly in order of execution)
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-to load the init binary are:
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+This document provides some high-level reasons for failure
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+(listed roughly in order of execution) to load the init binary.
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-A) Unable to mount root FS
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-B) init binary doesn't exist on rootfs
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-C) broken console device
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-D) binary exists but dependencies not available
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-E) binary cannot be loaded
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+1) **Unable to mount root FS**: Set "debug" kernel parameter (in bootloader
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+ config file or CONFIG_CMDLINE) to get more detailed kernel messages.
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-Detailed explanations:
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+2) **init binary doesn't exist on rootfs**: Make sure you have the correct
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+ root FS type (and ``root=`` kernel parameter points to the correct
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+ partition), required drivers such as storage hardware (such as SCSI or
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+ USB!) and filesystem (ext3, jffs2, etc.) are builtin (alternatively as
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+ modules, to be pre-loaded by an initrd).
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-A) Set "debug" kernel parameter (in bootloader config file or CONFIG_CMDLINE)
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- to get more detailed kernel messages.
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-B) make sure you have the correct root FS type
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- (and ``root=`` kernel parameter points to the correct partition),
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- required drivers such as storage hardware (such as SCSI or USB!)
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- and filesystem (ext3, jffs2 etc.) are builtin (alternatively as modules,
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- to be pre-loaded by an initrd)
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-C) Possibly a conflict in ``console= setup`` --> initial console unavailable.
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- E.g. some serial consoles are unreliable due to serial IRQ issues (e.g.
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- missing interrupt-based configuration).
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+3) **Broken console device**: Possibly a conflict in ``console= setup``
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+ --> initial console unavailable. E.g. some serial consoles are unreliable
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+ due to serial IRQ issues (e.g. missing interrupt-based configuration).
2721 Try using a different ``console= device`` or e.g. ``netconsole=``.
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-D) e.g. required library dependencies of the init binary such as
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- ``/lib/ld-linux.so.2`` missing or broken. Use
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- ``readelf -d <INIT>|grep NEEDED`` to find out which libraries are required.
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-E) make sure the binary's architecture matches your hardware.
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- E.g. i386 vs. x86_64 mismatch, or trying to load x86 on ARM hardware.
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- In case you tried loading a non-binary file here (shell script?),
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- you should make sure that the script specifies an interpreter in its shebang
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- header line (``#!/...``) that is fully working (including its library
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- dependencies). And before tackling scripts, better first test a simple
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- non-script binary such as ``/bin/sh`` and confirm its successful execution.
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- To find out more, add code ``to init/main.c`` to display kernel_execve()s
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- return values.
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+
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+4) **Binary exists but dependencies not available**: E.g. required library
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+ dependencies of the init binary such as ``/lib/ld-linux.so.2`` missing or
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+ broken. Use ``readelf -d <INIT>|grep NEEDED`` to find out which libraries
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+ are required.
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+
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+5) **Binary cannot be loaded**: Make sure the binary's architecture matches
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+ your hardware. E.g. i386 vs. x86_64 mismatch, or trying to load x86 on ARM
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+ hardware. In case you tried loading a non-binary file here (shell script?),
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+ you should make sure that the script specifies an interpreter in its
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+ shebang header line (``#!/...``) that is fully working (including its
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+ library dependencies). And before tackling scripts, better first test a
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+ simple non-script binary such as ``/bin/sh`` and confirm its successful
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+ execution. To find out more, add code ``to init/main.c`` to display
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+ kernel_execve()s return values.
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4138 Please extend this explanation whenever you find new failure causes
4239 (after all loading the init binary is a CRITICAL and hard transition step
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-which needs to be made as painless as possible), then submit patch to LKML.
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+which needs to be made as painless as possible), then submit a patch to LKML.
4441 Further TODOs:
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4643 - Implement the various ``run_init_process()`` invocations via a struct array
4744 which can then store the ``kernel_execve()`` result value and on failure
4845 log it all by iterating over **all** results (very important usability fix).
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-- try to make the implementation itself more helpful in general,
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- e.g. by providing additional error messages at affected places.
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+- Try to make the implementation itself more helpful in general, e.g. by
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+ providing additional error messages at affected places.
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-Andreas Mohr <andi at lisas period de>