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authorBorislav Petkov <bp@alien8.de>2011-07-23 13:39:29 -0400
committerLinus Torvalds <torvalds@linux-foundation.org>2011-07-23 13:58:08 -0400
commit807094c0b1c41344def32b249d9faf7b5ebeb1e7 (patch)
treef60bf86065f2ba91a6342de91f64351bc5750a4b /Documentation/sysctl
parent9fd615f466f6a463ebe05f04b2684cccc65c5317 (diff)
Documentation: refresh sysctl/kernel.txt
Refresh sysctl/kernel.txt. More specifically, - drop stale index entries - sync and sort index and entries - reflow sticking out paragraphs to colwidth 72 - correct typos - cleanup whitespace Signed-off-by: Borislav Petkov <bp@alien8.de> Signed-off-by: Randy Dunlap <rdunlap@xenotime.net> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'Documentation/sysctl')
-rw-r--r--Documentation/sysctl/kernel.txt215
1 files changed, 110 insertions, 105 deletions
diff --git a/Documentation/sysctl/kernel.txt b/Documentation/sysctl/kernel.txt
index 5e7cb39ad195..1c7fb0a94e28 100644
--- a/Documentation/sysctl/kernel.txt
+++ b/Documentation/sysctl/kernel.txt
@@ -17,23 +17,21 @@ before actually making adjustments.
17 17
18Currently, these files might (depending on your configuration) 18Currently, these files might (depending on your configuration)
19show up in /proc/sys/kernel: 19show up in /proc/sys/kernel:
20- acpi_video_flags 20
21- acct 21- acct
22- acpi_video_flags
23- auto_msgmni
22- bootloader_type [ X86 only ] 24- bootloader_type [ X86 only ]
23- bootloader_version [ X86 only ] 25- bootloader_version [ X86 only ]
24- callhome [ S390 only ] 26- callhome [ S390 only ]
25- auto_msgmni
26- core_pattern 27- core_pattern
27- core_pipe_limit 28- core_pipe_limit
28- core_uses_pid 29- core_uses_pid
29- ctrl-alt-del 30- ctrl-alt-del
30- dentry-state
31- dmesg_restrict 31- dmesg_restrict
32- domainname 32- domainname
33- hostname 33- hostname
34- hotplug 34- hotplug
35- java-appletviewer [ binfmt_java, obsolete ]
36- java-interpreter [ binfmt_java, obsolete ]
37- kptr_restrict 35- kptr_restrict
38- kstack_depth_to_print [ X86 only ] 36- kstack_depth_to_print [ X86 only ]
39- l2cr [ PPC only ] 37- l2cr [ PPC only ]
@@ -48,10 +46,14 @@ show up in /proc/sys/kernel:
48- overflowgid 46- overflowgid
49- overflowuid 47- overflowuid
50- panic 48- panic
49- panic_on_oops
50- panic_on_unrecovered_nmi
51- pid_max 51- pid_max
52- powersave-nap [ PPC only ] 52- powersave-nap [ PPC only ]
53- panic_on_unrecovered_nmi
54- printk 53- printk
54- printk_delay
55- printk_ratelimit
56- printk_ratelimit_burst
55- randomize_va_space 57- randomize_va_space
56- real-root-dev ==> Documentation/initrd.txt 58- real-root-dev ==> Documentation/initrd.txt
57- reboot-cmd [ SPARC only ] 59- reboot-cmd [ SPARC only ]
@@ -62,6 +64,7 @@ show up in /proc/sys/kernel:
62- shmall 64- shmall
63- shmmax [ sysv ipc ] 65- shmmax [ sysv ipc ]
64- shmmni 66- shmmni
67- softlockup_thresh
65- stop-a [ SPARC only ] 68- stop-a [ SPARC only ]
66- sysrq ==> Documentation/sysrq.txt 69- sysrq ==> Documentation/sysrq.txt
67- tainted 70- tainted
@@ -71,15 +74,6 @@ show up in /proc/sys/kernel:
71 74
72============================================================== 75==============================================================
73 76
74acpi_video_flags:
75
76flags
77
78See Doc*/kernel/power/video.txt, it allows mode of video boot to be
79set during run time.
80
81==============================================================
82
83acct: 77acct:
84 78
85highwater lowwater frequency 79highwater lowwater frequency
@@ -97,6 +91,25 @@ valid for 30 seconds.
97 91
98============================================================== 92==============================================================
99 93
94acpi_video_flags:
95
96flags
97
98See Doc*/kernel/power/video.txt, it allows mode of video boot to be
99set during run time.
100
101==============================================================
102
103auto_msgmni:
104
105Enables/Disables automatic recomputing of msgmni upon memory add/remove
106or upon ipc namespace creation/removal (see the msgmni description
107above). Echoing "1" into this file enables msgmni automatic recomputing.
108Echoing "0" turns it off. auto_msgmni default value is 1.
109
110
111==============================================================
112
100bootloader_type: 113bootloader_type:
101 114
102x86 bootloader identification 115x86 bootloader identification
@@ -172,22 +185,24 @@ core_pattern is used to specify a core dumpfile pattern name.
172 185
173core_pipe_limit: 186core_pipe_limit:
174 187
175This sysctl is only applicable when core_pattern is configured to pipe core 188This sysctl is only applicable when core_pattern is configured to pipe
176files to a user space helper (when the first character of core_pattern is a '|', 189core files to a user space helper (when the first character of
177see above). When collecting cores via a pipe to an application, it is 190core_pattern is a '|', see above). When collecting cores via a pipe
178occasionally useful for the collecting application to gather data about the 191to an application, it is occasionally useful for the collecting
179crashing process from its /proc/pid directory. In order to do this safely, the 192application to gather data about the crashing process from its
180kernel must wait for the collecting process to exit, so as not to remove the 193/proc/pid directory. In order to do this safely, the kernel must wait
181crashing processes proc files prematurely. This in turn creates the possibility 194for the collecting process to exit, so as not to remove the crashing
182that a misbehaving userspace collecting process can block the reaping of a 195processes proc files prematurely. This in turn creates the
183crashed process simply by never exiting. This sysctl defends against that. It 196possibility that a misbehaving userspace collecting process can block
184defines how many concurrent crashing processes may be piped to user space 197the reaping of a crashed process simply by never exiting. This sysctl
185applications in parallel. If this value is exceeded, then those crashing 198defends against that. It defines how many concurrent crashing
186processes above that value are noted via the kernel log and their cores are 199processes may be piped to user space applications in parallel. If
187skipped. 0 is a special value, indicating that unlimited processes may be 200this value is exceeded, then those crashing processes above that value
188captured in parallel, but that no waiting will take place (i.e. the collecting 201are noted via the kernel log and their cores are skipped. 0 is a
189process is not guaranteed access to /proc/<crashing pid>/). This value defaults 202special value, indicating that unlimited processes may be captured in
190to 0. 203parallel, but that no waiting will take place (i.e. the collecting
204process is not guaranteed access to /proc/<crashing pid>/). This
205value defaults to 0.
191 206
192============================================================== 207==============================================================
193 208
@@ -218,14 +233,14 @@ to decide what to do with it.
218 233
219dmesg_restrict: 234dmesg_restrict:
220 235
221This toggle indicates whether unprivileged users are prevented from using 236This toggle indicates whether unprivileged users are prevented
222dmesg(8) to view messages from the kernel's log buffer. When 237from using dmesg(8) to view messages from the kernel's log buffer.
223dmesg_restrict is set to (0) there are no restrictions. When 238When dmesg_restrict is set to (0) there are no restrictions. When
224dmesg_restrict is set set to (1), users must have CAP_SYSLOG to use 239dmesg_restrict is set set to (1), users must have CAP_SYSLOG to use
225dmesg(8). 240dmesg(8).
226 241
227The kernel config option CONFIG_SECURITY_DMESG_RESTRICT sets the default 242The kernel config option CONFIG_SECURITY_DMESG_RESTRICT sets the
228value of dmesg_restrict. 243default value of dmesg_restrict.
229 244
230============================================================== 245==============================================================
231 246
@@ -256,13 +271,6 @@ Default value is "/sbin/hotplug".
256 271
257============================================================== 272==============================================================
258 273
259l2cr: (PPC only)
260
261This flag controls the L2 cache of G3 processor boards. If
2620, the cache is disabled. Enabled if nonzero.
263
264==============================================================
265
266kptr_restrict: 274kptr_restrict:
267 275
268This toggle indicates whether restrictions are placed on 276This toggle indicates whether restrictions are placed on
@@ -283,6 +291,13 @@ kernel stack.
283 291
284============================================================== 292==============================================================
285 293
294l2cr: (PPC only)
295
296This flag controls the L2 cache of G3 processor boards. If
2970, the cache is disabled. Enabled if nonzero.
298
299==============================================================
300
286modules_disabled: 301modules_disabled:
287 302
288A toggle value indicating if modules are allowed to be loaded 303A toggle value indicating if modules are allowed to be loaded
@@ -293,6 +308,21 @@ to false.
293 308
294============================================================== 309==============================================================
295 310
311nmi_watchdog:
312
313Enables/Disables the NMI watchdog on x86 systems. When the value is
314non-zero the NMI watchdog is enabled and will continuously test all
315online cpus to determine whether or not they are still functioning
316properly. Currently, passing "nmi_watchdog=" parameter at boot time is
317required for this function to work.
318
319If LAPIC NMI watchdog method is in use (nmi_watchdog=2 kernel
320parameter), the NMI watchdog shares registers with oprofile. By
321disabling the NMI watchdog, oprofile may have more registers to
322utilize.
323
324==============================================================
325
296osrelease, ostype & version: 326osrelease, ostype & version:
297 327
298# cat osrelease 328# cat osrelease
@@ -312,10 +342,10 @@ The only way to tune these values is to rebuild the kernel :-)
312 342
313overflowgid & overflowuid: 343overflowgid & overflowuid:
314 344
315if your architecture did not always support 32-bit UIDs (i.e. arm, i386, 345if your architecture did not always support 32-bit UIDs (i.e. arm,
316m68k, sh, and sparc32), a fixed UID and GID will be returned to 346i386, m68k, sh, and sparc32), a fixed UID and GID will be returned to
317applications that use the old 16-bit UID/GID system calls, if the actual 347applications that use the old 16-bit UID/GID system calls, if the
318UID or GID would exceed 65535. 348actual UID or GID would exceed 65535.
319 349
320These sysctls allow you to change the value of the fixed UID and GID. 350These sysctls allow you to change the value of the fixed UID and GID.
321The default is 65534. 351The default is 65534.
@@ -324,9 +354,22 @@ The default is 65534.
324 354
325panic: 355panic:
326 356
327The value in this file represents the number of seconds the 357The value in this file represents the number of seconds the kernel
328kernel waits before rebooting on a panic. When you use the 358waits before rebooting on a panic. When you use the software watchdog,
329software watchdog, the recommended setting is 60. 359the recommended setting is 60.
360
361==============================================================
362
363panic_on_unrecovered_nmi:
364
365The default Linux behaviour on an NMI of either memory or unknown is
366to continue operation. For many environments such as scientific
367computing it is preferable that the box is taken out and the error
368dealt with than an uncorrected parity/ECC error get propagated.
369
370A small number of systems do generate NMI's for bizarre random reasons
371such as power management so the default is off. That sysctl works like
372the existing panic controls already in that directory.
330 373
331============================================================== 374==============================================================
332 375
@@ -376,6 +419,14 @@ the different loglevels.
376 419
377============================================================== 420==============================================================
378 421
422printk_delay:
423
424Delay each printk message in printk_delay milliseconds
425
426Value from 0 - 10000 is allowed.
427
428==============================================================
429
379printk_ratelimit: 430printk_ratelimit:
380 431
381Some warning messages are rate limited. printk_ratelimit specifies 432Some warning messages are rate limited. printk_ratelimit specifies
@@ -395,15 +446,7 @@ send before ratelimiting kicks in.
395 446
396============================================================== 447==============================================================
397 448
398printk_delay: 449randomize_va_space:
399
400Delay each printk message in printk_delay milliseconds
401
402Value from 0 - 10000 is allowed.
403
404==============================================================
405
406randomize-va-space:
407 450
408This option can be used to select the type of process address 451This option can be used to select the type of process address
409space randomization that is used in the system, for architectures 452space randomization that is used in the system, for architectures
@@ -466,11 +509,11 @@ are doing anyway :)
466 509
467============================================================== 510==============================================================
468 511
469shmmax: 512shmmax:
470 513
471This value can be used to query and set the run time limit 514This value can be used to query and set the run time limit
472on the maximum shared memory segment size that can be created. 515on the maximum shared memory segment size that can be created.
473Shared memory segments up to 1Gb are now supported in the 516Shared memory segments up to 1Gb are now supported in the
474kernel. This value defaults to SHMMAX. 517kernel. This value defaults to SHMMAX.
475 518
476============================================================== 519==============================================================
@@ -484,7 +527,7 @@ tunable to zero will disable the softlockup detection altogether.
484 527
485============================================================== 528==============================================================
486 529
487tainted: 530tainted:
488 531
489Non-zero if the kernel has been tainted. Numeric values, which 532Non-zero if the kernel has been tainted. Numeric values, which
490can be ORed together: 533can be ORed together:
@@ -509,49 +552,11 @@ can be ORed together:
509 552
510============================================================== 553==============================================================
511 554
512auto_msgmni:
513
514Enables/Disables automatic recomputing of msgmni upon memory add/remove or
515upon ipc namespace creation/removal (see the msgmni description above).
516Echoing "1" into this file enables msgmni automatic recomputing.
517Echoing "0" turns it off.
518auto_msgmni default value is 1.
519
520==============================================================
521
522nmi_watchdog:
523
524Enables/Disables the NMI watchdog on x86 systems. When the value is non-zero
525the NMI watchdog is enabled and will continuously test all online cpus to
526determine whether or not they are still functioning properly. Currently,
527passing "nmi_watchdog=" parameter at boot time is required for this function
528to work.
529
530If LAPIC NMI watchdog method is in use (nmi_watchdog=2 kernel parameter), the
531NMI watchdog shares registers with oprofile. By disabling the NMI watchdog,
532oprofile may have more registers to utilize.
533
534==============================================================
535
536unknown_nmi_panic: 555unknown_nmi_panic:
537 556
538The value in this file affects behavior of handling NMI. When the value is 557The value in this file affects behavior of handling NMI. When the
539non-zero, unknown NMI is trapped and then panic occurs. At that time, kernel 558value is non-zero, unknown NMI is trapped and then panic occurs. At
540debugging information is displayed on console. 559that time, kernel debugging information is displayed on console.
541
542NMI switch that most IA32 servers have fires unknown NMI up, for example.
543If a system hangs up, try pressing the NMI switch.
544
545==============================================================
546
547panic_on_unrecovered_nmi:
548
549The default Linux behaviour on an NMI of either memory or unknown is to continue
550operation. For many environments such as scientific computing it is preferable
551that the box is taken out and the error dealt with than an uncorrected
552parity/ECC error get propogated.
553
554A small number of systems do generate NMI's for bizarre random reasons such as
555power management so the default is off. That sysctl works like the existing
556panic controls already in that directory.
557 560
561NMI switch that most IA32 servers have fires unknown NMI up, for
562example. If a system hangs up, try pressing the NMI switch.