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Diffstat (limited to 'Documentation/admin-guide/sysrq.rst')
| -rw-r--r-- | Documentation/admin-guide/sysrq.rst | 48 |
1 files changed, 27 insertions, 21 deletions
diff --git a/Documentation/admin-guide/sysrq.rst b/Documentation/admin-guide/sysrq.rst index 72b2cfb066f4..0a178ef0111d 100644 --- a/Documentation/admin-guide/sysrq.rst +++ b/Documentation/admin-guide/sysrq.rst @@ -48,9 +48,10 @@ always allowed (by a user with admin privileges). How do I use the magic SysRq key? ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -On x86 - You press the key combo :kbd:`ALT-SysRq-<command key>`. +On x86 + You press the key combo :kbd:`ALT-SysRq-<command key>`. -.. note:: + .. note:: Some keyboards may not have a key labeled 'SysRq'. The 'SysRq' key is also known as the 'Print Screen' key. Also some keyboards cannot @@ -58,25 +59,28 @@ On x86 - You press the key combo :kbd:`ALT-SysRq-<command key>`. have better luck with press :kbd:`Alt`, press :kbd:`SysRq`, release :kbd:`SysRq`, press :kbd:`<command key>`, release everything. -On SPARC - You press :kbd:`ALT-STOP-<command key>`, I believe. +On SPARC + You press :kbd:`ALT-STOP-<command key>`, I believe. On the serial console (PC style standard serial ports only) You send a ``BREAK``, then within 5 seconds a command key. Sending ``BREAK`` twice is interpreted as a normal BREAK. On PowerPC - Press :kbd:`ALT - Print Screen` (or :kbd:`F13`) - :kbd:`<command key>`, + Press :kbd:`ALT - Print Screen` (or :kbd:`F13`) - :kbd:`<command key>`. :kbd:`Print Screen` (or :kbd:`F13`) - :kbd:`<command key>` may suffice. On other If you know of the key combos for other architectures, please - let me know so I can add them to this section. + submit a patch to be included in this section. On all - write a character to /proc/sysrq-trigger. e.g.:: + Write a character to /proc/sysrq-trigger. e.g.:: echo t > /proc/sysrq-trigger +The :kbd:`<command key>` is case sensitive. + What are the 'command' keys? ~~~~~~~~~~~~~~~~~~~~~~~~~~~~ @@ -86,8 +90,8 @@ Command Function ``b`` Will immediately reboot the system without syncing or unmounting your disks. -``c`` Will perform a system crash by a NULL pointer dereference. - A crashdump will be taken if configured. +``c`` Will perform a system crash and a crashdump will be taken + if configured. ``d`` Shows all locks that are held. @@ -201,10 +205,12 @@ frozen (probably root) filesystem via the FIFREEZE ioctl. Sometimes SysRq seems to get 'stuck' after using it, what can I do? ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -That happens to me, also. I've found that tapping shift, alt, and control -on both sides of the keyboard, and hitting an invalid sysrq sequence again -will fix the problem. (i.e., something like :kbd:`alt-sysrq-z`). Switching to -another virtual console (:kbd:`ALT+Fn`) and then back again should also help. +When this happens, try tapping shift, alt and control on both sides of the +keyboard, and hitting an invalid sysrq sequence again. (i.e., something like +:kbd:`alt-sysrq-z`). + +Switching to another virtual console (:kbd:`ALT+Fn`) and then back again +should also help. I hit SysRq, but nothing seems to happen, what's wrong? ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ @@ -229,13 +235,13 @@ prints help, and C) an action_msg string, that will print right before your handler is called. Your handler must conform to the prototype in 'sysrq.h'. After the ``sysrq_key_op`` is created, you can call the kernel function -``register_sysrq_key(int key, struct sysrq_key_op *op_p);`` this will +``register_sysrq_key(int key, const struct sysrq_key_op *op_p);`` this will register the operation pointed to by ``op_p`` at table key 'key', if that slot in the table is blank. At module unload time, you must call -the function ``unregister_sysrq_key(int key, struct sysrq_key_op *op_p)``, which -will remove the key op pointed to by 'op_p' from the key 'key', if and only if -it is currently registered in that slot. This is in case the slot has been -overwritten since you registered it. +the function ``unregister_sysrq_key(int key, const struct sysrq_key_op *op_p)``, +which will remove the key op pointed to by 'op_p' from the key 'key', if and +only if it is currently registered in that slot. This is in case the slot has +been overwritten since you registered it. The Magic SysRQ system works by registering key operations against a key op lookup table, which is defined in 'drivers/tty/sysrq.c'. This key table has @@ -282,7 +288,7 @@ Just ask them on the linux-kernel mailing list: Credits ~~~~~~~ -Written by Mydraal <vulpyne@vulpyne.net> -Updated by Adam Sulmicki <adam@cfar.umd.edu> -Updated by Jeremy M. Dolan <jmd@turbogeek.org> 2001/01/28 10:15:59 -Added to by Crutcher Dunnavant <crutcher+kernel@datastacks.com> +- Written by Mydraal <vulpyne@vulpyne.net> +- Updated by Adam Sulmicki <adam@cfar.umd.edu> +- Updated by Jeremy M. Dolan <jmd@turbogeek.org> 2001/01/28 10:15:59 +- Added to by Crutcher Dunnavant <crutcher+kernel@datastacks.com> |