diff options
Diffstat (limited to 'Documentation/sysctl/kernel.txt')
-rw-r--r-- | Documentation/sysctl/kernel.txt | 237 |
1 files changed, 132 insertions, 105 deletions
diff --git a/Documentation/sysctl/kernel.txt b/Documentation/sysctl/kernel.txt index 5e7cb39ad19..704e474a93d 100644 --- a/Documentation/sysctl/kernel.txt +++ b/Documentation/sysctl/kernel.txt | |||
@@ -17,23 +17,21 @@ before actually making adjustments. | |||
17 | 17 | ||
18 | Currently, these files might (depending on your configuration) | 18 | Currently, these files might (depending on your configuration) |
19 | show up in /proc/sys/kernel: | 19 | show 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 ] |
@@ -59,9 +61,11 @@ show up in /proc/sys/kernel: | |||
59 | - rtsig-nr | 61 | - rtsig-nr |
60 | - sem | 62 | - sem |
61 | - sg-big-buff [ generic SCSI device (sg) ] | 63 | - sg-big-buff [ generic SCSI device (sg) ] |
64 | - shm_rmid_forced | ||
62 | - shmall | 65 | - shmall |
63 | - shmmax [ sysv ipc ] | 66 | - shmmax [ sysv ipc ] |
64 | - shmmni | 67 | - shmmni |
68 | - softlockup_thresh | ||
65 | - stop-a [ SPARC only ] | 69 | - stop-a [ SPARC only ] |
66 | - sysrq ==> Documentation/sysrq.txt | 70 | - sysrq ==> Documentation/sysrq.txt |
67 | - tainted | 71 | - tainted |
@@ -71,15 +75,6 @@ show up in /proc/sys/kernel: | |||
71 | 75 | ||
72 | ============================================================== | 76 | ============================================================== |
73 | 77 | ||
74 | acpi_video_flags: | ||
75 | |||
76 | flags | ||
77 | |||
78 | See Doc*/kernel/power/video.txt, it allows mode of video boot to be | ||
79 | set during run time. | ||
80 | |||
81 | ============================================================== | ||
82 | |||
83 | acct: | 78 | acct: |
84 | 79 | ||
85 | highwater lowwater frequency | 80 | highwater lowwater frequency |
@@ -97,6 +92,25 @@ valid for 30 seconds. | |||
97 | 92 | ||
98 | ============================================================== | 93 | ============================================================== |
99 | 94 | ||
95 | acpi_video_flags: | ||
96 | |||
97 | flags | ||
98 | |||
99 | See Doc*/kernel/power/video.txt, it allows mode of video boot to be | ||
100 | set during run time. | ||
101 | |||
102 | ============================================================== | ||
103 | |||
104 | auto_msgmni: | ||
105 | |||
106 | Enables/Disables automatic recomputing of msgmni upon memory add/remove | ||
107 | or upon ipc namespace creation/removal (see the msgmni description | ||
108 | above). Echoing "1" into this file enables msgmni automatic recomputing. | ||
109 | Echoing "0" turns it off. auto_msgmni default value is 1. | ||
110 | |||
111 | |||
112 | ============================================================== | ||
113 | |||
100 | bootloader_type: | 114 | bootloader_type: |
101 | 115 | ||
102 | x86 bootloader identification | 116 | x86 bootloader identification |
@@ -172,22 +186,24 @@ core_pattern is used to specify a core dumpfile pattern name. | |||
172 | 186 | ||
173 | core_pipe_limit: | 187 | core_pipe_limit: |
174 | 188 | ||
175 | This sysctl is only applicable when core_pattern is configured to pipe core | 189 | This sysctl is only applicable when core_pattern is configured to pipe |
176 | files to a user space helper (when the first character of core_pattern is a '|', | 190 | core files to a user space helper (when the first character of |
177 | see above). When collecting cores via a pipe to an application, it is | 191 | core_pattern is a '|', see above). When collecting cores via a pipe |
178 | occasionally useful for the collecting application to gather data about the | 192 | to an application, it is occasionally useful for the collecting |
179 | crashing process from its /proc/pid directory. In order to do this safely, the | 193 | application to gather data about the crashing process from its |
180 | kernel must wait for the collecting process to exit, so as not to remove the | 194 | /proc/pid directory. In order to do this safely, the kernel must wait |
181 | crashing processes proc files prematurely. This in turn creates the possibility | 195 | for the collecting process to exit, so as not to remove the crashing |
182 | that a misbehaving userspace collecting process can block the reaping of a | 196 | processes proc files prematurely. This in turn creates the |
183 | crashed process simply by never exiting. This sysctl defends against that. It | 197 | possibility that a misbehaving userspace collecting process can block |
184 | defines how many concurrent crashing processes may be piped to user space | 198 | the reaping of a crashed process simply by never exiting. This sysctl |
185 | applications in parallel. If this value is exceeded, then those crashing | 199 | defends against that. It defines how many concurrent crashing |
186 | processes above that value are noted via the kernel log and their cores are | 200 | processes may be piped to user space applications in parallel. If |
187 | skipped. 0 is a special value, indicating that unlimited processes may be | 201 | this value is exceeded, then those crashing processes above that value |
188 | captured in parallel, but that no waiting will take place (i.e. the collecting | 202 | are noted via the kernel log and their cores are skipped. 0 is a |
189 | process is not guaranteed access to /proc/<crashing pid>/). This value defaults | 203 | special value, indicating that unlimited processes may be captured in |
190 | to 0. | 204 | parallel, but that no waiting will take place (i.e. the collecting |
205 | process is not guaranteed access to /proc/<crashing pid>/). This | ||
206 | value defaults to 0. | ||
191 | 207 | ||
192 | ============================================================== | 208 | ============================================================== |
193 | 209 | ||
@@ -218,14 +234,14 @@ to decide what to do with it. | |||
218 | 234 | ||
219 | dmesg_restrict: | 235 | dmesg_restrict: |
220 | 236 | ||
221 | This toggle indicates whether unprivileged users are prevented from using | 237 | This toggle indicates whether unprivileged users are prevented |
222 | dmesg(8) to view messages from the kernel's log buffer. When | 238 | from using dmesg(8) to view messages from the kernel's log buffer. |
223 | dmesg_restrict is set to (0) there are no restrictions. When | 239 | When dmesg_restrict is set to (0) there are no restrictions. When |
224 | dmesg_restrict is set set to (1), users must have CAP_SYSLOG to use | 240 | dmesg_restrict is set set to (1), users must have CAP_SYSLOG to use |
225 | dmesg(8). | 241 | dmesg(8). |
226 | 242 | ||
227 | The kernel config option CONFIG_SECURITY_DMESG_RESTRICT sets the default | 243 | The kernel config option CONFIG_SECURITY_DMESG_RESTRICT sets the |
228 | value of dmesg_restrict. | 244 | default value of dmesg_restrict. |
229 | 245 | ||
230 | ============================================================== | 246 | ============================================================== |
231 | 247 | ||
@@ -256,13 +272,6 @@ Default value is "/sbin/hotplug". | |||
256 | 272 | ||
257 | ============================================================== | 273 | ============================================================== |
258 | 274 | ||
259 | l2cr: (PPC only) | ||
260 | |||
261 | This flag controls the L2 cache of G3 processor boards. If | ||
262 | 0, the cache is disabled. Enabled if nonzero. | ||
263 | |||
264 | ============================================================== | ||
265 | |||
266 | kptr_restrict: | 275 | kptr_restrict: |
267 | 276 | ||
268 | This toggle indicates whether restrictions are placed on | 277 | This toggle indicates whether restrictions are placed on |
@@ -283,6 +292,13 @@ kernel stack. | |||
283 | 292 | ||
284 | ============================================================== | 293 | ============================================================== |
285 | 294 | ||
295 | l2cr: (PPC only) | ||
296 | |||
297 | This flag controls the L2 cache of G3 processor boards. If | ||
298 | 0, the cache is disabled. Enabled if nonzero. | ||
299 | |||
300 | ============================================================== | ||
301 | |||
286 | modules_disabled: | 302 | modules_disabled: |
287 | 303 | ||
288 | A toggle value indicating if modules are allowed to be loaded | 304 | A toggle value indicating if modules are allowed to be loaded |
@@ -293,6 +309,21 @@ to false. | |||
293 | 309 | ||
294 | ============================================================== | 310 | ============================================================== |
295 | 311 | ||
312 | nmi_watchdog: | ||
313 | |||
314 | Enables/Disables the NMI watchdog on x86 systems. When the value is | ||
315 | non-zero the NMI watchdog is enabled and will continuously test all | ||
316 | online cpus to determine whether or not they are still functioning | ||
317 | properly. Currently, passing "nmi_watchdog=" parameter at boot time is | ||
318 | required for this function to work. | ||
319 | |||
320 | If LAPIC NMI watchdog method is in use (nmi_watchdog=2 kernel | ||
321 | parameter), the NMI watchdog shares registers with oprofile. By | ||
322 | disabling the NMI watchdog, oprofile may have more registers to | ||
323 | utilize. | ||
324 | |||
325 | ============================================================== | ||
326 | |||
296 | osrelease, ostype & version: | 327 | osrelease, ostype & version: |
297 | 328 | ||
298 | # cat osrelease | 329 | # cat osrelease |
@@ -312,10 +343,10 @@ The only way to tune these values is to rebuild the kernel :-) | |||
312 | 343 | ||
313 | overflowgid & overflowuid: | 344 | overflowgid & overflowuid: |
314 | 345 | ||
315 | if your architecture did not always support 32-bit UIDs (i.e. arm, i386, | 346 | if your architecture did not always support 32-bit UIDs (i.e. arm, |
316 | m68k, sh, and sparc32), a fixed UID and GID will be returned to | 347 | i386, m68k, sh, and sparc32), a fixed UID and GID will be returned to |
317 | applications that use the old 16-bit UID/GID system calls, if the actual | 348 | applications that use the old 16-bit UID/GID system calls, if the |
318 | UID or GID would exceed 65535. | 349 | actual UID or GID would exceed 65535. |
319 | 350 | ||
320 | These sysctls allow you to change the value of the fixed UID and GID. | 351 | These sysctls allow you to change the value of the fixed UID and GID. |
321 | The default is 65534. | 352 | The default is 65534. |
@@ -324,9 +355,22 @@ The default is 65534. | |||
324 | 355 | ||
325 | panic: | 356 | panic: |
326 | 357 | ||
327 | The value in this file represents the number of seconds the | 358 | The value in this file represents the number of seconds the kernel |
328 | kernel waits before rebooting on a panic. When you use the | 359 | waits before rebooting on a panic. When you use the software watchdog, |
329 | software watchdog, the recommended setting is 60. | 360 | the recommended setting is 60. |
361 | |||
362 | ============================================================== | ||
363 | |||
364 | panic_on_unrecovered_nmi: | ||
365 | |||
366 | The default Linux behaviour on an NMI of either memory or unknown is | ||
367 | to continue operation. For many environments such as scientific | ||
368 | computing it is preferable that the box is taken out and the error | ||
369 | dealt with than an uncorrected parity/ECC error get propagated. | ||
370 | |||
371 | A small number of systems do generate NMI's for bizarre random reasons | ||
372 | such as power management so the default is off. That sysctl works like | ||
373 | the existing panic controls already in that directory. | ||
330 | 374 | ||
331 | ============================================================== | 375 | ============================================================== |
332 | 376 | ||
@@ -376,6 +420,14 @@ the different loglevels. | |||
376 | 420 | ||
377 | ============================================================== | 421 | ============================================================== |
378 | 422 | ||
423 | printk_delay: | ||
424 | |||
425 | Delay each printk message in printk_delay milliseconds | ||
426 | |||
427 | Value from 0 - 10000 is allowed. | ||
428 | |||
429 | ============================================================== | ||
430 | |||
379 | printk_ratelimit: | 431 | printk_ratelimit: |
380 | 432 | ||
381 | Some warning messages are rate limited. printk_ratelimit specifies | 433 | Some warning messages are rate limited. printk_ratelimit specifies |
@@ -395,15 +447,7 @@ send before ratelimiting kicks in. | |||
395 | 447 | ||
396 | ============================================================== | 448 | ============================================================== |
397 | 449 | ||
398 | printk_delay: | 450 | randomize_va_space: |
399 | |||
400 | Delay each printk message in printk_delay milliseconds | ||
401 | |||
402 | Value from 0 - 10000 is allowed. | ||
403 | |||
404 | ============================================================== | ||
405 | |||
406 | randomize-va-space: | ||
407 | 451 | ||
408 | This option can be used to select the type of process address | 452 | This option can be used to select the type of process address |
409 | space randomization that is used in the system, for architectures | 453 | space randomization that is used in the system, for architectures |
@@ -466,15 +510,36 @@ are doing anyway :) | |||
466 | 510 | ||
467 | ============================================================== | 511 | ============================================================== |
468 | 512 | ||
469 | shmmax: | 513 | shmmax: |
470 | 514 | ||
471 | This value can be used to query and set the run time limit | 515 | This value can be used to query and set the run time limit |
472 | on the maximum shared memory segment size that can be created. | 516 | on the maximum shared memory segment size that can be created. |
473 | Shared memory segments up to 1Gb are now supported in the | 517 | Shared memory segments up to 1Gb are now supported in the |
474 | kernel. This value defaults to SHMMAX. | 518 | kernel. This value defaults to SHMMAX. |
475 | 519 | ||
476 | ============================================================== | 520 | ============================================================== |
477 | 521 | ||
522 | shm_rmid_forced: | ||
523 | |||
524 | Linux lets you set resource limits, including how much memory one | ||
525 | process can consume, via setrlimit(2). Unfortunately, shared memory | ||
526 | segments are allowed to exist without association with any process, and | ||
527 | thus might not be counted against any resource limits. If enabled, | ||
528 | shared memory segments are automatically destroyed when their attach | ||
529 | count becomes zero after a detach or a process termination. It will | ||
530 | also destroy segments that were created, but never attached to, on exit | ||
531 | from the process. The only use left for IPC_RMID is to immediately | ||
532 | destroy an unattached segment. Of course, this breaks the way things are | ||
533 | defined, so some applications might stop working. Note that this | ||
534 | feature will do you no good unless you also configure your resource | ||
535 | limits (in particular, RLIMIT_AS and RLIMIT_NPROC). Most systems don't | ||
536 | need this. | ||
537 | |||
538 | Note that if you change this from 0 to 1, already created segments | ||
539 | without users and with a dead originative process will be destroyed. | ||
540 | |||
541 | ============================================================== | ||
542 | |||
478 | softlockup_thresh: | 543 | softlockup_thresh: |
479 | 544 | ||
480 | This value can be used to lower the softlockup tolerance threshold. The | 545 | This value can be used to lower the softlockup tolerance threshold. The |
@@ -484,7 +549,7 @@ tunable to zero will disable the softlockup detection altogether. | |||
484 | 549 | ||
485 | ============================================================== | 550 | ============================================================== |
486 | 551 | ||
487 | tainted: | 552 | tainted: |
488 | 553 | ||
489 | Non-zero if the kernel has been tainted. Numeric values, which | 554 | Non-zero if the kernel has been tainted. Numeric values, which |
490 | can be ORed together: | 555 | can be ORed together: |
@@ -509,49 +574,11 @@ can be ORed together: | |||
509 | 574 | ||
510 | ============================================================== | 575 | ============================================================== |
511 | 576 | ||
512 | auto_msgmni: | ||
513 | |||
514 | Enables/Disables automatic recomputing of msgmni upon memory add/remove or | ||
515 | upon ipc namespace creation/removal (see the msgmni description above). | ||
516 | Echoing "1" into this file enables msgmni automatic recomputing. | ||
517 | Echoing "0" turns it off. | ||
518 | auto_msgmni default value is 1. | ||
519 | |||
520 | ============================================================== | ||
521 | |||
522 | nmi_watchdog: | ||
523 | |||
524 | Enables/Disables the NMI watchdog on x86 systems. When the value is non-zero | ||
525 | the NMI watchdog is enabled and will continuously test all online cpus to | ||
526 | determine whether or not they are still functioning properly. Currently, | ||
527 | passing "nmi_watchdog=" parameter at boot time is required for this function | ||
528 | to work. | ||
529 | |||
530 | If LAPIC NMI watchdog method is in use (nmi_watchdog=2 kernel parameter), the | ||
531 | NMI watchdog shares registers with oprofile. By disabling the NMI watchdog, | ||
532 | oprofile may have more registers to utilize. | ||
533 | |||
534 | ============================================================== | ||
535 | |||
536 | unknown_nmi_panic: | 577 | unknown_nmi_panic: |
537 | 578 | ||
538 | The value in this file affects behavior of handling NMI. When the value is | 579 | The value in this file affects behavior of handling NMI. When the |
539 | non-zero, unknown NMI is trapped and then panic occurs. At that time, kernel | 580 | value is non-zero, unknown NMI is trapped and then panic occurs. At |
540 | debugging information is displayed on console. | 581 | that time, kernel debugging information is displayed on console. |
541 | |||
542 | NMI switch that most IA32 servers have fires unknown NMI up, for example. | ||
543 | If a system hangs up, try pressing the NMI switch. | ||
544 | |||
545 | ============================================================== | ||
546 | |||
547 | panic_on_unrecovered_nmi: | ||
548 | |||
549 | The default Linux behaviour on an NMI of either memory or unknown is to continue | ||
550 | operation. For many environments such as scientific computing it is preferable | ||
551 | that the box is taken out and the error dealt with than an uncorrected | ||
552 | parity/ECC error get propogated. | ||
553 | |||
554 | A small number of systems do generate NMI's for bizarre random reasons such as | ||
555 | power management so the default is off. That sysctl works like the existing | ||
556 | panic controls already in that directory. | ||
557 | 582 | ||
583 | NMI switch that most IA32 servers have fires unknown NMI up, for | ||
584 | example. If a system hangs up, try pressing the NMI switch. | ||