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linux-next/Documentation/ABI/testing/pstore
Luck, Tony 366f7e7a79 pstore: use mount option instead sysfs to tweak kmsg_bytes
/sys/fs is a somewhat strange way to tweak what could more
obviously be tuned with a mount option.

Suggested-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-03-21 13:50:05 -07:00

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Where: /dev/pstore/...
Date: March 2011
Kernel Version: 2.6.39
Contact: tony.luck@intel.com
Description: Generic interface to platform dependent persistent storage.
Platforms that provide a mechanism to preserve some data
across system reboots can register with this driver to
provide a generic interface to show records captured in
the dying moments. In the case of a panic the last part
of the console log is captured, but other interesting
data can also be saved.
# mount -t pstore -o kmsg_bytes=8000 - /dev/pstore
$ ls -l /dev/pstore
total 0
-r--r--r-- 1 root root 7896 Nov 30 15:38 dmesg-erst-1
Different users of this interface will result in different
filename prefixes. Currently two are defined:
"dmesg" - saved console log
"mce" - architecture dependent data from fatal h/w error
Once the information in a file has been read, removing
the file will signal to the underlying persistent storage
device that it can reclaim the space for later re-use.
$ rm /dev/pstore/dmesg-erst-1
The expectation is that all files in /dev/pstore
will be saved elsewhere and erased from persistent store
soon after boot to free up space ready for the next
catastrophe.
The 'kmsg_bytes' mount option changes the target amount of
data saved on each oops/panic. Pstore saves (possibly
multiple) files based on the record size of the underlying
persistent storage until at least this amount is reached.
Default is 10 Kbytes.