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Based on kernel version 3.15.4. Page generated on 2014-07-07 09:04 EST.

1	Documentation for /proc/sys/kernel/*	kernel version 2.2.10
2		(c) 1998, 1999,  Rik van Riel <riel@nl.linux.org>
3		(c) 2009,        Shen Feng<shen@cn.fujitsu.com>
4	
5	For general info and legal blurb, please look in README.
6	
7	==============================================================
8	
9	This file contains documentation for the sysctl files in
10	/proc/sys/kernel/ and is valid for Linux kernel version 2.2.
11	
12	The files in this directory can be used to tune and monitor
13	miscellaneous and general things in the operation of the Linux
14	kernel. Since some of the files _can_ be used to screw up your
15	system, it is advisable to read both documentation and source
16	before actually making adjustments.
17	
18	Currently, these files might (depending on your configuration)
19	show up in /proc/sys/kernel:
20	
21	- acct
22	- acpi_video_flags
23	- auto_msgmni
24	- bootloader_type	     [ X86 only ]
25	- bootloader_version	     [ X86 only ]
26	- callhome		     [ S390 only ]
27	- cap_last_cap
28	- core_pattern
29	- core_pipe_limit
30	- core_uses_pid
31	- ctrl-alt-del
32	- dmesg_restrict
33	- domainname
34	- hostname
35	- hotplug
36	- hung_task_panic
37	- hung_task_check_count
38	- hung_task_timeout_secs
39	- hung_task_warnings
40	- kexec_load_disabled
41	- kptr_restrict
42	- kstack_depth_to_print       [ X86 only ]
43	- l2cr                        [ PPC only ]
44	- modprobe                    ==> Documentation/debugging-modules.txt
45	- modules_disabled
46	- msg_next_id		      [ sysv ipc ]
47	- msgmax
48	- msgmnb
49	- msgmni
50	- nmi_watchdog
51	- osrelease
52	- ostype
53	- overflowgid
54	- overflowuid
55	- panic
56	- panic_on_oops
57	- panic_on_unrecovered_nmi
58	- panic_on_stackoverflow
59	- pid_max
60	- powersave-nap               [ PPC only ]
61	- printk
62	- printk_delay
63	- printk_ratelimit
64	- printk_ratelimit_burst
65	- randomize_va_space
66	- real-root-dev               ==> Documentation/initrd.txt
67	- reboot-cmd                  [ SPARC only ]
68	- rtsig-max
69	- rtsig-nr
70	- sem
71	- sem_next_id		      [ sysv ipc ]
72	- sg-big-buff                 [ generic SCSI device (sg) ]
73	- shm_next_id		      [ sysv ipc ]
74	- shm_rmid_forced
75	- shmall
76	- shmmax                      [ sysv ipc ]
77	- shmmni
78	- stop-a                      [ SPARC only ]
79	- sysrq                       ==> Documentation/sysrq.txt
80	- tainted
81	- threads-max
82	- unknown_nmi_panic
83	- watchdog_thresh
84	- version
85	
86	==============================================================
87	
88	acct:
89	
90	highwater lowwater frequency
91	
92	If BSD-style process accounting is enabled these values control
93	its behaviour. If free space on filesystem where the log lives
94	goes below <lowwater>% accounting suspends. If free space gets
95	above <highwater>% accounting resumes. <Frequency> determines
96	how often do we check the amount of free space (value is in
97	seconds). Default:
98	4 2 30
99	That is, suspend accounting if there left <= 2% free; resume it
100	if we got >=4%; consider information about amount of free space
101	valid for 30 seconds.
102	
103	==============================================================
104	
105	acpi_video_flags:
106	
107	flags
108	
109	See Doc*/kernel/power/video.txt, it allows mode of video boot to be
110	set during run time.
111	
112	==============================================================
113	
114	auto_msgmni:
115	
116	Enables/Disables automatic recomputing of msgmni upon memory add/remove
117	or upon ipc namespace creation/removal (see the msgmni description
118	above). Echoing "1" into this file enables msgmni automatic recomputing.
119	Echoing "0" turns it off. auto_msgmni default value is 1.
120	
121	
122	==============================================================
123	
124	bootloader_type:
125	
126	x86 bootloader identification
127	
128	This gives the bootloader type number as indicated by the bootloader,
129	shifted left by 4, and OR'd with the low four bits of the bootloader
130	version.  The reason for this encoding is that this used to match the
131	type_of_loader field in the kernel header; the encoding is kept for
132	backwards compatibility.  That is, if the full bootloader type number
133	is 0x15 and the full version number is 0x234, this file will contain
134	the value 340 = 0x154.
135	
136	See the type_of_loader and ext_loader_type fields in
137	Documentation/x86/boot.txt for additional information.
138	
139	==============================================================
140	
141	bootloader_version:
142	
143	x86 bootloader version
144	
145	The complete bootloader version number.  In the example above, this
146	file will contain the value 564 = 0x234.
147	
148	See the type_of_loader and ext_loader_ver fields in
149	Documentation/x86/boot.txt for additional information.
150	
151	==============================================================
152	
153	callhome:
154	
155	Controls the kernel's callhome behavior in case of a kernel panic.
156	
157	The s390 hardware allows an operating system to send a notification
158	to a service organization (callhome) in case of an operating system panic.
159	
160	When the value in this file is 0 (which is the default behavior)
161	nothing happens in case of a kernel panic. If this value is set to "1"
162	the complete kernel oops message is send to the IBM customer service
163	organization in case the mainframe the Linux operating system is running
164	on has a service contract with IBM.
165	
166	==============================================================
167	
168	cap_last_cap
169	
170	Highest valid capability of the running kernel.  Exports
171	CAP_LAST_CAP from the kernel.
172	
173	==============================================================
174	
175	core_pattern:
176	
177	core_pattern is used to specify a core dumpfile pattern name.
178	. max length 128 characters; default value is "core"
179	. core_pattern is used as a pattern template for the output filename;
180	  certain string patterns (beginning with '%') are substituted with
181	  their actual values.
182	. backward compatibility with core_uses_pid:
183		If core_pattern does not include "%p" (default does not)
184		and core_uses_pid is set, then .PID will be appended to
185		the filename.
186	. corename format specifiers:
187		%<NUL>	'%' is dropped
188		%%	output one '%'
189		%p	pid
190		%P	global pid (init PID namespace)
191		%u	uid
192		%g	gid
193		%d	dump mode, matches PR_SET_DUMPABLE and
194			/proc/sys/fs/suid_dumpable
195		%s	signal number
196		%t	UNIX time of dump
197		%h	hostname
198		%e	executable filename (may be shortened)
199		%E	executable path
200		%<OTHER> both are dropped
201	. If the first character of the pattern is a '|', the kernel will treat
202	  the rest of the pattern as a command to run.  The core dump will be
203	  written to the standard input of that program instead of to a file.
204	
205	==============================================================
206	
207	core_pipe_limit:
208	
209	This sysctl is only applicable when core_pattern is configured to pipe
210	core files to a user space helper (when the first character of
211	core_pattern is a '|', see above).  When collecting cores via a pipe
212	to an application, it is occasionally useful for the collecting
213	application to gather data about the crashing process from its
214	/proc/pid directory.  In order to do this safely, the kernel must wait
215	for the collecting process to exit, so as not to remove the crashing
216	processes proc files prematurely.  This in turn creates the
217	possibility that a misbehaving userspace collecting process can block
218	the reaping of a crashed process simply by never exiting.  This sysctl
219	defends against that.  It defines how many concurrent crashing
220	processes may be piped to user space applications in parallel.  If
221	this value is exceeded, then those crashing processes above that value
222	are noted via the kernel log and their cores are skipped.  0 is a
223	special value, indicating that unlimited processes may be captured in
224	parallel, but that no waiting will take place (i.e. the collecting
225	process is not guaranteed access to /proc/<crashing pid>/).  This
226	value defaults to 0.
227	
228	==============================================================
229	
230	core_uses_pid:
231	
232	The default coredump filename is "core".  By setting
233	core_uses_pid to 1, the coredump filename becomes core.PID.
234	If core_pattern does not include "%p" (default does not)
235	and core_uses_pid is set, then .PID will be appended to
236	the filename.
237	
238	==============================================================
239	
240	ctrl-alt-del:
241	
242	When the value in this file is 0, ctrl-alt-del is trapped and
243	sent to the init(1) program to handle a graceful restart.
244	When, however, the value is > 0, Linux's reaction to a Vulcan
245	Nerve Pinch (tm) will be an immediate reboot, without even
246	syncing its dirty buffers.
247	
248	Note: when a program (like dosemu) has the keyboard in 'raw'
249	mode, the ctrl-alt-del is intercepted by the program before it
250	ever reaches the kernel tty layer, and it's up to the program
251	to decide what to do with it.
252	
253	==============================================================
254	
255	dmesg_restrict:
256	
257	This toggle indicates whether unprivileged users are prevented
258	from using dmesg(8) to view messages from the kernel's log buffer.
259	When dmesg_restrict is set to (0) there are no restrictions. When
260	dmesg_restrict is set set to (1), users must have CAP_SYSLOG to use
261	dmesg(8).
262	
263	The kernel config option CONFIG_SECURITY_DMESG_RESTRICT sets the
264	default value of dmesg_restrict.
265	
266	==============================================================
267	
268	domainname & hostname:
269	
270	These files can be used to set the NIS/YP domainname and the
271	hostname of your box in exactly the same way as the commands
272	domainname and hostname, i.e.:
273	# echo "darkstar" > /proc/sys/kernel/hostname
274	# echo "mydomain" > /proc/sys/kernel/domainname
275	has the same effect as
276	# hostname "darkstar"
277	# domainname "mydomain"
278	
279	Note, however, that the classic darkstar.frop.org has the
280	hostname "darkstar" and DNS (Internet Domain Name Server)
281	domainname "frop.org", not to be confused with the NIS (Network
282	Information Service) or YP (Yellow Pages) domainname. These two
283	domain names are in general different. For a detailed discussion
284	see the hostname(1) man page.
285	
286	==============================================================
287	
288	hotplug:
289	
290	Path for the hotplug policy agent.
291	Default value is "/sbin/hotplug".
292	
293	==============================================================
294	
295	hung_task_panic:
296	
297	Controls the kernel's behavior when a hung task is detected.
298	This file shows up if CONFIG_DETECT_HUNG_TASK is enabled.
299	
300	0: continue operation. This is the default behavior.
301	
302	1: panic immediately.
303	
304	==============================================================
305	
306	hung_task_check_count:
307	
308	The upper bound on the number of tasks that are checked.
309	This file shows up if CONFIG_DETECT_HUNG_TASK is enabled.
310	
311	==============================================================
312	
313	hung_task_timeout_secs:
314	
315	Check interval. When a task in D state did not get scheduled
316	for more than this value report a warning.
317	This file shows up if CONFIG_DETECT_HUNG_TASK is enabled.
318	
319	0: means infinite timeout - no checking done.
320	Possible values to set are in range {0..LONG_MAX/HZ}.
321	
322	==============================================================
323	
324	hung_task_warnings:
325	
326	The maximum number of warnings to report. During a check interval
327	if a hung task is detected, this value is decreased by 1.
328	When this value reaches 0, no more warnings will be reported.
329	This file shows up if CONFIG_DETECT_HUNG_TASK is enabled.
330	
331	-1: report an infinite number of warnings.
332	
333	==============================================================
334	
335	kexec_load_disabled:
336	
337	A toggle indicating if the kexec_load syscall has been disabled. This
338	value defaults to 0 (false: kexec_load enabled), but can be set to 1
339	(true: kexec_load disabled). Once true, kexec can no longer be used, and
340	the toggle cannot be set back to false. This allows a kexec image to be
341	loaded before disabling the syscall, allowing a system to set up (and
342	later use) an image without it being altered. Generally used together
343	with the "modules_disabled" sysctl.
344	
345	==============================================================
346	
347	kptr_restrict:
348	
349	This toggle indicates whether restrictions are placed on
350	exposing kernel addresses via /proc and other interfaces.
351	
352	When kptr_restrict is set to (0), the default, there are no restrictions.
353	
354	When kptr_restrict is set to (1), kernel pointers printed using the %pK
355	format specifier will be replaced with 0's unless the user has CAP_SYSLOG
356	and effective user and group ids are equal to the real ids. This is
357	because %pK checks are done at read() time rather than open() time, so
358	if permissions are elevated between the open() and the read() (e.g via
359	a setuid binary) then %pK will not leak kernel pointers to unprivileged
360	users. Note, this is a temporary solution only. The correct long-term
361	solution is to do the permission checks at open() time. Consider removing
362	world read permissions from files that use %pK, and using dmesg_restrict
363	to protect against uses of %pK in dmesg(8) if leaking kernel pointer
364	values to unprivileged users is a concern.
365	
366	When kptr_restrict is set to (2), kernel pointers printed using
367	%pK will be replaced with 0's regardless of privileges.
368	
369	==============================================================
370	
371	kstack_depth_to_print: (X86 only)
372	
373	Controls the number of words to print when dumping the raw
374	kernel stack.
375	
376	==============================================================
377	
378	l2cr: (PPC only)
379	
380	This flag controls the L2 cache of G3 processor boards. If
381	0, the cache is disabled. Enabled if nonzero.
382	
383	==============================================================
384	
385	modules_disabled:
386	
387	A toggle value indicating if modules are allowed to be loaded
388	in an otherwise modular kernel.  This toggle defaults to off
389	(0), but can be set true (1).  Once true, modules can be
390	neither loaded nor unloaded, and the toggle cannot be set back
391	to false.  Generally used with the "kexec_load_disabled" toggle.
392	
393	==============================================================
394	
395	msg_next_id, sem_next_id, and shm_next_id:
396	
397	These three toggles allows to specify desired id for next allocated IPC
398	object: message, semaphore or shared memory respectively.
399	
400	By default they are equal to -1, which means generic allocation logic.
401	Possible values to set are in range {0..INT_MAX}.
402	
403	Notes:
404	1) kernel doesn't guarantee, that new object will have desired id. So,
405	it's up to userspace, how to handle an object with "wrong" id.
406	2) Toggle with non-default value will be set back to -1 by kernel after
407	successful IPC object allocation.
408	
409	==============================================================
410	
411	nmi_watchdog:
412	
413	Enables/Disables the NMI watchdog on x86 systems. When the value is
414	non-zero the NMI watchdog is enabled and will continuously test all
415	online cpus to determine whether or not they are still functioning
416	properly. Currently, passing "nmi_watchdog=" parameter at boot time is
417	required for this function to work.
418	
419	If LAPIC NMI watchdog method is in use (nmi_watchdog=2 kernel
420	parameter), the NMI watchdog shares registers with oprofile. By
421	disabling the NMI watchdog, oprofile may have more registers to
422	utilize.
423	
424	==============================================================
425	
426	numa_balancing
427	
428	Enables/disables automatic page fault based NUMA memory
429	balancing. Memory is moved automatically to nodes
430	that access it often.
431	
432	Enables/disables automatic NUMA memory balancing. On NUMA machines, there
433	is a performance penalty if remote memory is accessed by a CPU. When this
434	feature is enabled the kernel samples what task thread is accessing memory
435	by periodically unmapping pages and later trapping a page fault. At the
436	time of the page fault, it is determined if the data being accessed should
437	be migrated to a local memory node.
438	
439	The unmapping of pages and trapping faults incur additional overhead that
440	ideally is offset by improved memory locality but there is no universal
441	guarantee. If the target workload is already bound to NUMA nodes then this
442	feature should be disabled. Otherwise, if the system overhead from the
443	feature is too high then the rate the kernel samples for NUMA hinting
444	faults may be controlled by the numa_balancing_scan_period_min_ms,
445	numa_balancing_scan_delay_ms, numa_balancing_scan_period_max_ms,
446	numa_balancing_scan_size_mb, and numa_balancing_settle_count sysctls.
447	
448	==============================================================
449	
450	numa_balancing_scan_period_min_ms, numa_balancing_scan_delay_ms,
451	numa_balancing_scan_period_max_ms, numa_balancing_scan_size_mb
452	
453	Automatic NUMA balancing scans tasks address space and unmaps pages to
454	detect if pages are properly placed or if the data should be migrated to a
455	memory node local to where the task is running.  Every "scan delay" the task
456	scans the next "scan size" number of pages in its address space. When the
457	end of the address space is reached the scanner restarts from the beginning.
458	
459	In combination, the "scan delay" and "scan size" determine the scan rate.
460	When "scan delay" decreases, the scan rate increases.  The scan delay and
461	hence the scan rate of every task is adaptive and depends on historical
462	behaviour. If pages are properly placed then the scan delay increases,
463	otherwise the scan delay decreases.  The "scan size" is not adaptive but
464	the higher the "scan size", the higher the scan rate.
465	
466	Higher scan rates incur higher system overhead as page faults must be
467	trapped and potentially data must be migrated. However, the higher the scan
468	rate, the more quickly a tasks memory is migrated to a local node if the
469	workload pattern changes and minimises performance impact due to remote
470	memory accesses. These sysctls control the thresholds for scan delays and
471	the number of pages scanned.
472	
473	numa_balancing_scan_period_min_ms is the minimum time in milliseconds to
474	scan a tasks virtual memory. It effectively controls the maximum scanning
475	rate for each task.
476	
477	numa_balancing_scan_delay_ms is the starting "scan delay" used for a task
478	when it initially forks.
479	
480	numa_balancing_scan_period_max_ms is the maximum time in milliseconds to
481	scan a tasks virtual memory. It effectively controls the minimum scanning
482	rate for each task.
483	
484	numa_balancing_scan_size_mb is how many megabytes worth of pages are
485	scanned for a given scan.
486	
487	==============================================================
488	
489	osrelease, ostype & version:
490	
491	# cat osrelease
492	2.1.88
493	# cat ostype
494	Linux
495	# cat version
496	#5 Wed Feb 25 21:49:24 MET 1998
497	
498	The files osrelease and ostype should be clear enough. Version
499	needs a little more clarification however. The '#5' means that
500	this is the fifth kernel built from this source base and the
501	date behind it indicates the time the kernel was built.
502	The only way to tune these values is to rebuild the kernel :-)
503	
504	==============================================================
505	
506	overflowgid & overflowuid:
507	
508	if your architecture did not always support 32-bit UIDs (i.e. arm,
509	i386, m68k, sh, and sparc32), a fixed UID and GID will be returned to
510	applications that use the old 16-bit UID/GID system calls, if the
511	actual UID or GID would exceed 65535.
512	
513	These sysctls allow you to change the value of the fixed UID and GID.
514	The default is 65534.
515	
516	==============================================================
517	
518	panic:
519	
520	The value in this file represents the number of seconds the kernel
521	waits before rebooting on a panic. When you use the software watchdog,
522	the recommended setting is 60.
523	
524	==============================================================
525	
526	panic_on_unrecovered_nmi:
527	
528	The default Linux behaviour on an NMI of either memory or unknown is
529	to continue operation. For many environments such as scientific
530	computing it is preferable that the box is taken out and the error
531	dealt with than an uncorrected parity/ECC error get propagated.
532	
533	A small number of systems do generate NMI's for bizarre random reasons
534	such as power management so the default is off. That sysctl works like
535	the existing panic controls already in that directory.
536	
537	==============================================================
538	
539	panic_on_oops:
540	
541	Controls the kernel's behaviour when an oops or BUG is encountered.
542	
543	0: try to continue operation
544	
545	1: panic immediately.  If the `panic' sysctl is also non-zero then the
546	   machine will be rebooted.
547	
548	==============================================================
549	
550	panic_on_stackoverflow:
551	
552	Controls the kernel's behavior when detecting the overflows of
553	kernel, IRQ and exception stacks except a user stack.
554	This file shows up if CONFIG_DEBUG_STACKOVERFLOW is enabled.
555	
556	0: try to continue operation.
557	
558	1: panic immediately.
559	
560	==============================================================
561	
562	perf_cpu_time_max_percent:
563	
564	Hints to the kernel how much CPU time it should be allowed to
565	use to handle perf sampling events.  If the perf subsystem
566	is informed that its samples are exceeding this limit, it
567	will drop its sampling frequency to attempt to reduce its CPU
568	usage.
569	
570	Some perf sampling happens in NMIs.  If these samples
571	unexpectedly take too long to execute, the NMIs can become
572	stacked up next to each other so much that nothing else is
573	allowed to execute.
574	
575	0: disable the mechanism.  Do not monitor or correct perf's
576	   sampling rate no matter how CPU time it takes.
577	
578	1-100: attempt to throttle perf's sample rate to this
579	   percentage of CPU.  Note: the kernel calculates an
580	   "expected" length of each sample event.  100 here means
581	   100% of that expected length.  Even if this is set to
582	   100, you may still see sample throttling if this
583	   length is exceeded.  Set to 0 if you truly do not care
584	   how much CPU is consumed.
585	
586	==============================================================
587	
588	
589	pid_max:
590	
591	PID allocation wrap value.  When the kernel's next PID value
592	reaches this value, it wraps back to a minimum PID value.
593	PIDs of value pid_max or larger are not allocated.
594	
595	==============================================================
596	
597	ns_last_pid:
598	
599	The last pid allocated in the current (the one task using this sysctl
600	lives in) pid namespace. When selecting a pid for a next task on fork
601	kernel tries to allocate a number starting from this one.
602	
603	==============================================================
604	
605	powersave-nap: (PPC only)
606	
607	If set, Linux-PPC will use the 'nap' mode of powersaving,
608	otherwise the 'doze' mode will be used.
609	
610	==============================================================
611	
612	printk:
613	
614	The four values in printk denote: console_loglevel,
615	default_message_loglevel, minimum_console_loglevel and
616	default_console_loglevel respectively.
617	
618	These values influence printk() behavior when printing or
619	logging error messages. See 'man 2 syslog' for more info on
620	the different loglevels.
621	
622	- console_loglevel: messages with a higher priority than
623	  this will be printed to the console
624	- default_message_loglevel: messages without an explicit priority
625	  will be printed with this priority
626	- minimum_console_loglevel: minimum (highest) value to which
627	  console_loglevel can be set
628	- default_console_loglevel: default value for console_loglevel
629	
630	==============================================================
631	
632	printk_delay:
633	
634	Delay each printk message in printk_delay milliseconds
635	
636	Value from 0 - 10000 is allowed.
637	
638	==============================================================
639	
640	printk_ratelimit:
641	
642	Some warning messages are rate limited. printk_ratelimit specifies
643	the minimum length of time between these messages (in jiffies), by
644	default we allow one every 5 seconds.
645	
646	A value of 0 will disable rate limiting.
647	
648	==============================================================
649	
650	printk_ratelimit_burst:
651	
652	While long term we enforce one message per printk_ratelimit
653	seconds, we do allow a burst of messages to pass through.
654	printk_ratelimit_burst specifies the number of messages we can
655	send before ratelimiting kicks in.
656	
657	==============================================================
658	
659	randomize_va_space:
660	
661	This option can be used to select the type of process address
662	space randomization that is used in the system, for architectures
663	that support this feature.
664	
665	0 - Turn the process address space randomization off.  This is the
666	    default for architectures that do not support this feature anyways,
667	    and kernels that are booted with the "norandmaps" parameter.
668	
669	1 - Make the addresses of mmap base, stack and VDSO page randomized.
670	    This, among other things, implies that shared libraries will be
671	    loaded to random addresses.  Also for PIE-linked binaries, the
672	    location of code start is randomized.  This is the default if the
673	    CONFIG_COMPAT_BRK option is enabled.
674	
675	2 - Additionally enable heap randomization.  This is the default if
676	    CONFIG_COMPAT_BRK is disabled.
677	
678	    There are a few legacy applications out there (such as some ancient
679	    versions of libc.so.5 from 1996) that assume that brk area starts
680	    just after the end of the code+bss.  These applications break when
681	    start of the brk area is randomized.  There are however no known
682	    non-legacy applications that would be broken this way, so for most
683	    systems it is safe to choose full randomization.
684	
685	    Systems with ancient and/or broken binaries should be configured
686	    with CONFIG_COMPAT_BRK enabled, which excludes the heap from process
687	    address space randomization.
688	
689	==============================================================
690	
691	reboot-cmd: (Sparc only)
692	
693	??? This seems to be a way to give an argument to the Sparc
694	ROM/Flash boot loader. Maybe to tell it what to do after
695	rebooting. ???
696	
697	==============================================================
698	
699	rtsig-max & rtsig-nr:
700	
701	The file rtsig-max can be used to tune the maximum number
702	of POSIX realtime (queued) signals that can be outstanding
703	in the system.
704	
705	rtsig-nr shows the number of RT signals currently queued.
706	
707	==============================================================
708	
709	sg-big-buff:
710	
711	This file shows the size of the generic SCSI (sg) buffer.
712	You can't tune it just yet, but you could change it on
713	compile time by editing include/scsi/sg.h and changing
714	the value of SG_BIG_BUFF.
715	
716	There shouldn't be any reason to change this value. If
717	you can come up with one, you probably know what you
718	are doing anyway :)
719	
720	==============================================================
721	
722	shmall:
723	
724	This parameter sets the total amount of shared memory pages that
725	can be used system wide. Hence, SHMALL should always be at least
726	ceil(shmmax/PAGE_SIZE).
727	
728	If you are not sure what the default PAGE_SIZE is on your Linux
729	system, you can run the following command:
730	
731	# getconf PAGE_SIZE
732	
733	==============================================================
734	
735	shmmax:
736	
737	This value can be used to query and set the run time limit
738	on the maximum shared memory segment size that can be created.
739	Shared memory segments up to 1Gb are now supported in the
740	kernel.  This value defaults to SHMMAX.
741	
742	==============================================================
743	
744	shm_rmid_forced:
745	
746	Linux lets you set resource limits, including how much memory one
747	process can consume, via setrlimit(2).  Unfortunately, shared memory
748	segments are allowed to exist without association with any process, and
749	thus might not be counted against any resource limits.  If enabled,
750	shared memory segments are automatically destroyed when their attach
751	count becomes zero after a detach or a process termination.  It will
752	also destroy segments that were created, but never attached to, on exit
753	from the process.  The only use left for IPC_RMID is to immediately
754	destroy an unattached segment.  Of course, this breaks the way things are
755	defined, so some applications might stop working.  Note that this
756	feature will do you no good unless you also configure your resource
757	limits (in particular, RLIMIT_AS and RLIMIT_NPROC).  Most systems don't
758	need this.
759	
760	Note that if you change this from 0 to 1, already created segments
761	without users and with a dead originative process will be destroyed.
762	
763	==============================================================
764	
765	tainted:
766	
767	Non-zero if the kernel has been tainted.  Numeric values, which
768	can be ORed together:
769	
770	   1 - A module with a non-GPL license has been loaded, this
771	       includes modules with no license.
772	       Set by modutils >= 2.4.9 and module-init-tools.
773	   2 - A module was force loaded by insmod -f.
774	       Set by modutils >= 2.4.9 and module-init-tools.
775	   4 - Unsafe SMP processors: SMP with CPUs not designed for SMP.
776	   8 - A module was forcibly unloaded from the system by rmmod -f.
777	  16 - A hardware machine check error occurred on the system.
778	  32 - A bad page was discovered on the system.
779	  64 - The user has asked that the system be marked "tainted".  This
780	       could be because they are running software that directly modifies
781	       the hardware, or for other reasons.
782	 128 - The system has died.
783	 256 - The ACPI DSDT has been overridden with one supplied by the user
784	        instead of using the one provided by the hardware.
785	 512 - A kernel warning has occurred.
786	1024 - A module from drivers/staging was loaded.
787	2048 - The system is working around a severe firmware bug.
788	4096 - An out-of-tree module has been loaded.
789	8192 - An unsigned module has been loaded in a kernel supporting module
790	       signature.
791	
792	==============================================================
793	
794	unknown_nmi_panic:
795	
796	The value in this file affects behavior of handling NMI. When the
797	value is non-zero, unknown NMI is trapped and then panic occurs. At
798	that time, kernel debugging information is displayed on console.
799	
800	NMI switch that most IA32 servers have fires unknown NMI up, for
801	example.  If a system hangs up, try pressing the NMI switch.
802	
803	==============================================================
804	
805	watchdog_thresh:
806	
807	This value can be used to control the frequency of hrtimer and NMI
808	events and the soft and hard lockup thresholds. The default threshold
809	is 10 seconds.
810	
811	The softlockup threshold is (2 * watchdog_thresh). Setting this
812	tunable to zero will disable lockup detection altogether.
813	
814	==============================================================
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