/proc/sysrq-trigger详解

http://itnihao.blog.51cto.com/1741976/830374

# 立即重新启动计算机
echo "b" > /proc/sysrq-trigger

 

# 立即关闭计算机
echo "o" > /proc/sysrq-trigger

 

# 导出内存分配的信息 （可以用/var/log/message 查看）
echo "m" > /proc/sysrq-trigger

 

# 导出当前CPU寄存器信息和标志位的信息
echo "p" > /proc/sysrq-trigger

 

# 导出线程状态信息
echo "t" > /proc/sysrq-trigger

 

# 故意让系统崩溃
echo "c" > /proc/sysrq-trigger

 

# 立即重新挂载所有的文件系统 
echo "s" > /proc/sysrq-trigger

 

# 立即重新挂载所有的文件系统为只读
echo "u" > /proc/sysrq-trigger

 

Documentation for sysrq.c

 

Based on kernel version 2.6.38. Page generated on 2011-03-22 22:20 EST.

 

1       Linux Magic System Request Key Hacks

2       Documentation for sysrq.c

3      

4       * What is the magic SysRq key?

5       ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

6       It is a 'magical' key combo you can hit which the kernel will respond to

7       regardless of whatever else it is doing, unless it is completely locked up.

8      

9       * How do I enable the magic SysRq key?

10     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

11     You need to say "yes" to 'Magic SysRq key (CONFIG_MAGIC_SYSRQ)' when

12     configuring the kernel. When running a kernel with SysRq compiled in,

13     /proc/sys/kernel/sysrq controls the functions allowed to be invoked via

14     the SysRq key. By default the file contains 1 which means that every

15     possible SysRq request is allowed (in older versions SysRq was disabled

16     by default, and you were required to specifically enable it at run-time

17     but this is not the case any more). Here is the list of possible values

18     in /proc/sys/kernel/sysrq:

19        0 - disable sysrq completely

20        1 - enable all functions of sysrq

21      >1 - bitmask of allowed sysrq functions (see below for detailed function

22            description):

23               2 - enable control of console logging level

24               4 - enable control of keyboard (SAK, unraw)

25               8 - enable debugging dumps of processes etc.

26              16 - enable sync command

27              32 - enable remount read-only

28              64 - enable signalling of processes (term, kill, oom-kill)

29             128 - allow reboot/poweroff

30             256 - allow nicing of all RT tasks

31    

32     You can set the value in the file by the following command:

33         echo "number" >/proc/sys/kernel/sysrq

34    

35     Note that the value of /proc/sys/kernel/sysrq influences only the invocation

36     via a keyboard. Invocation of any operation via /proc/sysrq-trigger is always

37     allowed (by a user with admin privileges).

38    

39     * How do I use the magic SysRq key?

40     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

41     On x86   - You press the key combo 'ALT-SysRq-<command key>'. Note - Some

42                keyboards may not have a key labeled 'SysRq'. The 'SysRq' key is

43                also known as the 'Print Screen' key. Also some keyboards cannot

44                 handle so many keys being pressed at the same time, so you might

45                 have better luck with "press Alt", "press SysRq", "release SysRq",

46                 "press <command key>", release everything.

47    

48     On SPARC - You press 'ALT-STOP-<command key>', I believe.

49    

50     On the serial console (PC style standard serial ports only) -

51                You send a BREAK, then within 5 seconds a command key. Sending

52                BREAK twice is interpreted as a normal BREAK.

53    

54     On PowerPC - Press 'ALT - Print Screen (or F13) - <command key>, 

55                  Print Screen (or F13) - <command key> may suffice.

56    

57     On other - If you know of the key combos for other architectures, please

58                let me know so I can add them to this section.

59    

60     On all - write a character to /proc/sysrq-trigger. e.g.:

61    

62                       echo t > /proc/sysrq-trigger

63    

64     * What are the 'command' keys?

65     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

66     'b'     - Will immediately reboot the system without syncing or unmounting

67               your disks.

68    

69     'c'     - Will perform a system crash by a NULL pointer dereference.

 

# 立即重新启动计算机

　　echo "b" > /proc/sysrq-trigger

　　# 立即关闭计算机

　　echo "o" > /proc/sysrq-trigger

　　# 导出内存分配的信息 （可以用/var/log/message 查看）

　　echo "m" > /proc/sysrq-trigger

　　# 导出当前CPU寄存器信息和标志位的信息

　　echo "p" > /proc/sysrq-trigger

　　# 导出线程状态信息

　　echo "t" > /proc/sysrq-trigger

　　# 故意让系统崩溃

　　echo "c" > /proc/sysrq-trigger

　　# 立即重新挂载所有的文件系统

　　echo "s" > /proc/sysrq-trigger

　　# 立即重新挂载所有的文件系统为只读

　　echo "u" > /proc/sysrq-trigger