xref: /openbmc/linux/Documentation/ABI/testing/pstore (revision ba61bb17)
1Where:		/sys/fs/pstore/... (or /dev/pstore/...)
2Date:		March 2011
3Kernel Version: 2.6.39
4Contact:	tony.luck@intel.com
5Description:	Generic interface to platform dependent persistent storage.
6
7		Platforms that provide a mechanism to preserve some data
8		across system reboots can register with this driver to
9		provide a generic interface to show records captured in
10		the dying moments.  In the case of a panic the last part
11		of the console log is captured, but other interesting
12		data can also be saved.
13
14		# mount -t pstore -o kmsg_bytes=8000 - /sys/fs/pstore
15
16		$ ls -l /sys/fs/pstore/
17		total 0
18		-r--r--r-- 1 root root 7896 Nov 30 15:38 dmesg-erst-1
19
20		Different users of this interface will result in different
21		filename prefixes.  Currently two are defined:
22
23		"dmesg"	- saved console log
24		"mce"	- architecture dependent data from fatal h/w error
25
26		Once the information in a file has been read, removing
27		the file will signal to the underlying persistent storage
28		device that it can reclaim the space for later re-use.
29
30		$ rm /sys/fs/pstore/dmesg-erst-1
31
32		The expectation is that all files in /sys/fs/pstore/
33		will be saved elsewhere and erased from persistent store
34		soon after boot to free up space ready for the next
35		catastrophe.
36
37		The 'kmsg_bytes' mount option changes the target amount of
38		data saved on each oops/panic. Pstore saves (possibly
39		multiple) files based on the record size of the underlying
40		persistent storage until at least this amount is reached.
41		Default is 10 Kbytes.
42
43		Pstore only supports one backend at a time. If multiple
44		backends are available, the preferred backend may be
45		set by passing the pstore.backend= argument to the kernel at
46		boot time.
47
48