1 What: /sys/fs/pstore/... !! 1 What: /sys/fs/pstore/... (or /dev/pstore/...)
2 What: /dev/pstore/... <<
3 Date: March 2011 2 Date: March 2011
4 KernelVersion: 2.6.39 3 KernelVersion: 2.6.39
5 Contact: tony.luck@intel.com 4 Contact: tony.luck@intel.com
6 Description: Generic interface to platform 5 Description: Generic interface to platform dependent persistent storage.
7 6
8 Platforms that provide a mecha 7 Platforms that provide a mechanism to preserve some data
9 across system reboots can regi 8 across system reboots can register with this driver to
10 provide a generic interface to 9 provide a generic interface to show records captured in
11 the dying moments. In the cas 10 the dying moments. In the case of a panic the last part
12 of the console log is captured 11 of the console log is captured, but other interesting
13 data can also be saved:: 12 data can also be saved::
14 13
15 # mount -t pstore -o kmsg_ 14 # mount -t pstore -o kmsg_bytes=8000 - /sys/fs/pstore
16 15
17 $ ls -l /sys/fs/pstore/ 16 $ ls -l /sys/fs/pstore/
18 total 0 17 total 0
19 -r--r--r-- 1 root root 789 18 -r--r--r-- 1 root root 7896 Nov 30 15:38 dmesg-erst-1
20 19
21 Different users of this interf 20 Different users of this interface will result in different
22 filename prefixes. Currently 21 filename prefixes. Currently two are defined:
23 22
24 - "dmesg" - saved console log 23 - "dmesg" - saved console log
25 - "mce" - architecture depen 24 - "mce" - architecture dependent data from fatal h/w error
26 25
27 Once the information in a file 26 Once the information in a file has been read, removing
28 the file will signal to the un 27 the file will signal to the underlying persistent storage
29 device that it can reclaim the 28 device that it can reclaim the space for later re-use::
30 29
31 $ rm /sys/fs/pstore/dmesg- 30 $ rm /sys/fs/pstore/dmesg-erst-1
32 31
33 The expectation is that all fi 32 The expectation is that all files in /sys/fs/pstore/
34 will be saved elsewhere and er 33 will be saved elsewhere and erased from persistent store
35 soon after boot to free up spa 34 soon after boot to free up space ready for the next
36 catastrophe. 35 catastrophe.
37 36
38 The 'kmsg_bytes' mount option 37 The 'kmsg_bytes' mount option changes the target amount of
39 data saved on each oops/panic. 38 data saved on each oops/panic. Pstore saves (possibly
40 multiple) files based on the r 39 multiple) files based on the record size of the underlying
41 persistent storage until at le 40 persistent storage until at least this amount is reached.
42 Default is 10 Kbytes. 41 Default is 10 Kbytes.
43 42
44 Pstore only supports one backe 43 Pstore only supports one backend at a time. If multiple
45 backends are available, the pr 44 backends are available, the preferred backend may be
46 set by passing the pstore.back 45 set by passing the pstore.backend= argument to the kernel at
47 boot time. 46 boot time.
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