systemd-pstore(8) - phpMan

SYSTEMD-PSTORE.SERVICE(8) systemd-pstore.service SYSTEMD-PSTORE.SERVICE(8)

NAME
systemd-pstore.service, systemd-pstore - A service to archive contents of pstore

SYNOPSIS
/lib/systemd/systemd-pstore

systemd-pstore.service

DESCRIPTION
systemd-pstore.service is a system service that archives the contents of the Linux
persistent storage filesystem, pstore, to other storage, thus preserving the existing
information contained in the pstore, and clearing pstore storage for future error events.

Linux provides a persistent storage file system, pstore, that can store error records when
the kernel dies (or reboots or powers-off). These records in turn can be referenced to
debug kernel problems (currently the kernel stores the tail of the kernel log, which also
contains a stack backtrace, into pstore).

The pstore file system supports a variety of backends that map onto persistent storage,
such as the ACPI ERST and UEFI variables. The pstore backends typically offer a relatively
small amount of persistent storage, e.g. 64KiB, which can quickly fill up and thus prevent
subsequent kernel crashes from recording errors. Thus there is a need to monitor and
extract the pstore contents so that future kernel problems can also record information in
the pstore.

The pstore service is independent of the kdump service. In cloud environments
specifically, host and guest filesystems are on remote filesystems (e.g. iSCSI or NFS),
thus kdump relies (implicitly and/or explicitly) upon proper operation of networking
software *and* hardware *and* infrastructure. Thus it may not be possible to capture a
kernel coredump to a file since writes over the network may not be possible.

The pstore backend, on the other hand, is completely local and provides a path to store
error records which will survive a reboot and aid in post-mortem debugging.

The systemd-pstore executable does the actual work. Upon starting, the pstore.conf file is
read and the /sys/fs/pstore/ directory contents are processed according to the options.
Pstore files are written to the journal, and optionally saved into
/var/lib/systemd/pstore/.

CONFIGURATION
The behavior of systemd-pstore is configured through the configuration file
/etc/systemd/pstore.conf and corresponding snippets /etc/systemd/pstore.conf.d/*.conf, see
pstore.conf(5).

Disabling pstore processing
To disable pstore processing by systemd-pstore, set

Storage=none

in pstore.conf(5).

Kernel parameters
The kernel has two parameters, /sys/module/kernel/parameters/crash_kexec_post_notifiers
and /sys/module/printk/parameters/always_kmsg_dump, that control writes into pstore. The
first enables storing of the kernel log (including stack trace) into pstore upon a panic
or crash, and the second enables storing of the kernel log upon a normal shutdown
(shutdown, reboot, halt). These parameters can be managed via the tmpfiles.d(5) mechanism,
specifically the file /usr/lib/tmpfiles/systemd-pstore.conf.

USAGE
Data stored in the journal can be viewed with journalctl(1) as usual.