# 立即重新啟動計算機
echo "b" > /proc/sysrq-trigger
# 立即關閉計算機
echo "o" > /proc/sysrq-trigger
# 導出內存分配的信息 （可以用/var/log/message 查看）
echo "m" > /proc/sysrq-trigger
# 導出當前CPU寄存器信息和標志位的信息
echo "p" > /proc/sysrq-trigger
# 導出線程狀態信息
echo "t" > /proc/sysrq-trigger
# 故意讓系統崩潰
echo "c" > /proc/sysrq-trigger
# 立即重新掛載所有的文件系統
echo "s" > /proc/sysrq-trigger
# 立即重新掛載所有的文件系統為只讀
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.
# 立即重新啟動計算機
echo "b" > /proc/sysrq-trigger
# 立即關閉計算機
echo "o" > /proc/sysrq-trigger
# 導出內存分配的信息 （可以用/var/log/message 查看）
echo "m" > /proc/sysrq-trigger
# 導出當前CPU寄存器信息和標志位的信息
echo "p" > /proc/sysrq-trigger
# 導出線程狀態信息
echo "t" > /proc/sysrq-trigger
# 故意讓系統崩潰
echo "c" > /proc/sysrq-trigger
# 立即重新掛載所有的文件系統
echo "s" > /proc/sysrq-trigger
# 立即重新掛載所有的文件系統為只讀
echo "u" > /proc/sysrq-trigger
下面將sysrq.txt中的內容附加上一段，全部可以使用的command：
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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.
70 A crashdump will be taken if configured.
71
72 'd' - Shows all locks that are held.
73
74 'e' - Send a SIGTERM to all processes, except for init.
75
76 'f' - Will call oom_kill to kill a memory hog process.
77
78 'g' - Used by kgdb on ppc and sh platforms.
79
80 'h' - Will display help (actually any other key than those listed
81 here will display help. but 'h' is easy to remember :-)
82
83 'i' - Send a SIGKILL to all processes, except for init.
84
85 'j' - Forcibly "Just thaw it" - filesystems frozen by the FIFREEZE ioctl.
86
87 'k' - Secure Access Key (SAK) Kills all programs on the current virtual
88 console. NOTE: See important comments below in SAK section.
89
90 'l' - Shows a stack backtrace for all active CPUs.
91
92 'm' - Will dump current memory info to your console.
93
94 'n' - Used to make RT tasks nice-able
95
96 'o' - Will shut your system off (if configured and supported).
97
98 'p' - Will dump the current registers and flags to your console.
99
100 'q' - Will dump per CPU lists of all armed hrtimers (but NOT regular
101 timer_list timers) and detailed information about all
102 clockevent devices.
103
104 'r' - Turns off keyboard raw mode and sets it to XLATE.
105
106 's' - Will attempt to sync all mounted filesystems.
107
108 't' - Will dump a list of current tasks and their information to your
109 console.
110
111 'u' - Will attempt to remount all mounted filesystems read-only.
112
113 'v' - Dumps Voyager SMP processor info to your console.
114
115 'w' - Dumps tasks that are in uninterruptable (blocked) state.
116
117 'x' - Used by xmon interface on ppc/powerpc platforms.
118
119 'z' - Dump the ftrace buffer
120
121 '0'-'9' - Sets the console log level, controlling which kernel messages
122 will be printed to your console. ('0', for example would make
123 it so that only emergency messages like PANICs or OOPSes would
124 make it to your console.)
125
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