Documentation/power/shutdown-debugging.rst

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Linux kernel

Corpus path

Documentation/power/shutdown-debugging.rst

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.rst

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1726 bytes

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54

Domain

Support Tooling And Documentation

Bucket

Documentation

Inferred role

Support Tooling And Documentation: documentation

Status

atlas-only

Why This File Exists

Repository support layer: documentation, build tooling, samples, user-space helper tools, generated initramfs support, licenses, and validation utilities.

• Repository support layer: documentation, build tooling, samples, user-space helper tools, generated initramfs support, licenses, and validation utilities.

Dependency Surface

• No C-style include directives detected by the generator.

Detected Declarations

• No top-level syscall, struct, function, initcall, or export declaration detected by the generator.

Annotated Snippet

.. SPDX-License-Identifier: GPL-2.0

Debugging Kernel Shutdown Hangs with pstore
+++++++++++++++++++++++++++++++++++++++++++

Overview
========
If the system hangs while shutting down, the kernel logs may need to be
retrieved to debug the issue.

On systems that have a UART available, it is best to configure the kernel to use
this UART for kernel console output.

If a UART isn't available, the ``pstore`` subsystem provides a mechanism to
persist this data across a system reset, allowing it to be retrieved on the next
boot.

Kernel Configuration
====================
To enable ``pstore`` and enable saving kernel ring buffer logs, set the
following kernel configuration options:

* ``CONFIG_PSTORE=y``
* ``CONFIG_PSTORE_CONSOLE=y``

Additionally, enable a backend to store the data. Depending upon your platform
some potential options include:

* ``CONFIG_EFI_VARS_PSTORE=y``
* ``CONFIG_PSTORE_RAM=y``
* ``CONFIG_CHROMEOS_PSTORE=y``
* ``CONFIG_PSTORE_BLK=y``

Kernel Command-line Parameters
==============================
Add these parameters to your kernel command line:

* ``printk.always_kmsg_dump=Y``
	* Forces the kernel to dump the entire message buffer to pstore during
		shutdown
* ``efi_pstore.pstore_disable=N``
	* For EFI-based systems, ensures the EFI backend is active

Userspace Interaction and Log Retrieval
=======================================
On the next boot after a hang, pstore logs will be available in the pstore
filesystem (``/sys/fs/pstore``) and can be retrieved by userspace.

On systemd systems, the ``systemd-pstore`` service will help do the following:

#. Locate pstore data in ``/sys/fs/pstore``
#. Read and save it to ``/var/lib/systemd/pstore``
#. Clear pstore data for the next event

Annotation

• Atlas domain: Support Tooling And Documentation / Documentation.
• Implementation status: atlas-only.

Implementation Notes

• This generated page is the file-by-file coverage layer; curated subsystem chapters should link here when they synthesize a multi-file control flow.
• Core OS pages should be promoted from atlas-only to deep-reviewed when they explain data structures, invariants, locking, lifecycle, and C implementation snippets.
• Driver-family pages are intentionally pattern-oriented unless they are part of the selected PCIe/NVMe representative device path.