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Diffstat (limited to 'Documentation/sysrq.txt')
| -rw-r--r-- | Documentation/sysrq.txt | 28 |
1 files changed, 15 insertions, 13 deletions
diff --git a/Documentation/sysrq.txt b/Documentation/sysrq.txt index 8cb4d7842a5f..0e307c94809a 100644 --- a/Documentation/sysrq.txt +++ b/Documentation/sysrq.txt @@ -11,27 +11,29 @@ regardless of whatever else it is doing, unless it is completely locked up. You need to say "yes" to 'Magic SysRq key (CONFIG_MAGIC_SYSRQ)' when configuring the kernel. When running a kernel with SysRq compiled in, /proc/sys/kernel/sysrq controls the functions allowed to be invoked via -the SysRq key. By default the file contains 1 which means that every -possible SysRq request is allowed (in older versions SysRq was disabled -by default, and you were required to specifically enable it at run-time -but this is not the case any more). Here is the list of possible values -in /proc/sys/kernel/sysrq: +the SysRq key. The default value in this file is set by the +CONFIG_MAGIC_SYSRQ_DEFAULT_ENABLE config symbol, which itself defaults +to 1. Here is the list of possible values in /proc/sys/kernel/sysrq: 0 - disable sysrq completely 1 - enable all functions of sysrq >1 - bitmask of allowed sysrq functions (see below for detailed function description): - 2 - enable control of console logging level - 4 - enable control of keyboard (SAK, unraw) - 8 - enable debugging dumps of processes etc. - 16 - enable sync command - 32 - enable remount read-only - 64 - enable signalling of processes (term, kill, oom-kill) - 128 - allow reboot/poweroff - 256 - allow nicing of all RT tasks + 2 = 0x2 - enable control of console logging level + 4 = 0x4 - enable control of keyboard (SAK, unraw) + 8 = 0x8 - enable debugging dumps of processes etc. + 16 = 0x10 - enable sync command + 32 = 0x20 - enable remount read-only + 64 = 0x40 - enable signalling of processes (term, kill, oom-kill) + 128 = 0x80 - allow reboot/poweroff + 256 = 0x100 - allow nicing of all RT tasks You can set the value in the file by the following command: echo "number" >/proc/sys/kernel/sysrq +The number may be written here either as decimal or as hexadecimal +with the 0x prefix. CONFIG_MAGIC_SYSRQ_DEFAULT_ENABLE must always be +written in hexadecimal. + Note that the value of /proc/sys/kernel/sysrq influences only the invocation via a keyboard. Invocation of any operation via /proc/sysrq-trigger is always allowed (by a user with admin privileges). |