Lines Matching refs:the
9 This file contains documentation for the sysctl files in
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
98 its behaviour. If free space on filesystem where the log lives
101 how often do we check the amount of free space (value is in
135 This gives the bootloader type number as indicated by the bootloader,
136 shifted left by 4, and OR'd with the low four bits of the bootloader
137 version. The reason for this encoding is that this used to match the
138 type_of_loader field in the kernel header; the encoding is kept for
139 backwards compatibility. That is, if the full bootloader type number
140 is 0x15 and the full version number is 0x234, this file will contain
141 the value 340 = 0x154.
143 See the type_of_loader and ext_loader_type fields in
152 The complete bootloader version number. In the example above, this
153 file will contain the value 564 = 0x234.
155 See the type_of_loader and ext_loader_ver fields in
162 Controls the kernel's callhome behavior in case of a kernel panic.
167 When the value in this file is 0 (which is the default behavior)
169 the complete kernel oops message is send to the IBM customer service
170 organization in case the mainframe the Linux operating system is running
177 Highest valid capability of the running kernel. Exports
178 CAP_LAST_CAP from the kernel.
186 . core_pattern is used as a pattern template for the output filename;
192 the filename.
210 . If the first character of the pattern is a '|', the kernel will treat
211 the rest of the pattern as a command to run. The core dump will be
212 written to the standard input of that program instead of to a file.
219 core files to a user space helper (when the first character of
221 to an application, it is occasionally useful for the collecting
222 application to gather data about the crashing process from its
223 /proc/pid directory. In order to do this safely, the kernel must wait
224 for the collecting process to exit, so as not to remove the crashing
225 processes proc files prematurely. This in turn creates the
227 the reaping of a crashed process simply by never exiting. This sysctl
231 are noted via the kernel log and their cores are skipped. 0 is a
233 parallel, but that no waiting will take place (i.e. the collecting
242 core_uses_pid to 1, the coredump filename becomes core.PID.
245 the filename.
251 When the value in this file is 0, ctrl-alt-del is trapped and
252 sent to the init(1) program to handle a graceful restart.
253 When, however, the value is > 0, Linux's reaction to a Vulcan
257 Note: when a program (like dosemu) has the keyboard in 'raw'
258 mode, the ctrl-alt-del is intercepted by the program before it
259 ever reaches the kernel tty layer, and it's up to the program
267 from using dmesg(8) to view messages from the kernel's log buffer.
272 The kernel config option CONFIG_SECURITY_DMESG_RESTRICT sets the
279 These files can be used to set the NIS/YP domainname and the
280 hostname of your box in exactly the same way as the commands
284 has the same effect as
288 Note, however, that the classic darkstar.frop.org has the
290 domainname "frop.org", not to be confused with the NIS (Network
293 see the hostname(1) man page.
299 Path for the hotplug policy agent.
306 Controls the kernel's behavior when a hung task is detected.
309 0: continue operation. This is the default behavior.
317 The upper bound on the number of tasks that are checked.
346 A toggle indicating if the kexec_load syscall has been disabled. This
349 the toggle cannot be set back to false. This allows a kexec image to be
350 loaded before disabling the syscall, allowing a system to set up (and
352 with the "modules_disabled" sysctl.
361 When kptr_restrict is set to (0), the default, there are no restrictions.
363 When kptr_restrict is set to (1), kernel pointers printed using the %pK
364 format specifier will be replaced with 0's unless the user has CAP_SYSLOG
365 and effective user and group ids are equal to the real ids. This is
367 if permissions are elevated between the open() and the read() (e.g via
370 solution is to do the permission checks at open() time. Consider removing
382 Controls the number of words to print when dumping the raw
389 This flag controls the L2 cache of G3 processor boards. If
390 0, the cache is disabled. Enabled if nonzero.
399 neither loaded nor unloaded, and the toggle cannot be set back
400 to false. Generally used with the "kexec_load_disabled" toggle.
422 This parameter can be used to control the NMI watchdog
423 (i.e. the hard lockup detector) on x86 systems.
425 0 - disable the hard lockup detector
426 1 - enable the hard lockup detector
431 while a CPU is busy. Hence, the alternative name 'NMI watchdog'.
433 The NMI watchdog is disabled by default if the kernel is running as a guest
438 to the guest kernel command line (see Documentation/kernel-parameters.txt).
450 feature is enabled the kernel samples what task thread is accessing memory
451 by periodically unmapping pages and later trapping a page fault. At the
452 time of the page fault, it is determined if the data being accessed should
457 guarantee. If the target workload is already bound to NUMA nodes then this
458 feature should be disabled. Otherwise, if the system overhead from the
459 feature is too high then the rate the kernel samples for NUMA hinting
460 faults may be controlled by the numa_balancing_scan_period_min_ms,
470 detect if pages are properly placed or if the data should be migrated to a
471 memory node local to where the task is running. Every "scan delay" the task
472 scans the next "scan size" number of pages in its address space. When the
473 end of the address space is reached the scanner restarts from the beginning.
475 In combination, the "scan delay" and "scan size" determine the scan rate.
476 When "scan delay" decreases, the scan rate increases. The scan delay and
477 hence the scan rate of every task is adaptive and depends on historical
478 behaviour. If pages are properly placed then the scan delay increases,
479 otherwise the scan delay decreases. The "scan size" is not adaptive but
480 the higher the "scan size", the higher the scan rate.
483 trapped and potentially data must be migrated. However, the higher the scan
484 rate, the more quickly a tasks memory is migrated to a local node if the
486 memory accesses. These sysctls control the thresholds for scan delays and
487 the number of pages scanned.
489 numa_balancing_scan_period_min_ms is the minimum time in milliseconds to
490 scan a tasks virtual memory. It effectively controls the maximum scanning
493 numa_balancing_scan_delay_ms is the starting "scan delay" used for a task
496 numa_balancing_scan_period_max_ms is the maximum time in milliseconds to
497 scan a tasks virtual memory. It effectively controls the minimum scanning
516 this is the fifth kernel built from this source base and the
517 date behind it indicates the time the kernel was built.
518 The only way to tune these values is to rebuild the kernel :-)
526 applications that use the old 16-bit UID/GID system calls, if the
529 These sysctls allow you to change the value of the fixed UID and GID.
536 The value in this file represents the number of seconds the kernel
537 waits before rebooting on a panic. When you use the software watchdog,
538 the recommended setting is 60.
544 Controls the kernel's behaviour when an oops or BUG is encountered.
548 1: panic immediately. If the `panic' sysctl is also non-zero then the
555 Controls the kernel's behavior when detecting the overflows of
569 computing it is preferable that the box is taken out and the error
573 such as power management so the default is off. That sysctl works like
574 the existing panic controls already in that directory.
580 Calls panic() in the WARN() path when set to 1. This is useful to avoid
581 a kernel rebuild when attempting to kdump at the location of a WARN().
591 Hints to the kernel how much CPU time it should be allowed to
592 use to handle perf sampling events. If the perf subsystem
598 unexpectedly take too long to execute, the NMIs can become
602 0: disable the mechanism. Do not monitor or correct perf's
606 percentage of CPU. Note: the kernel calculates an
618 PID allocation wrap value. When the kernel's next PID value
626 The last pid allocated in the current (the one task using this sysctl
634 If set, Linux-PPC will use the 'nap' mode of powersaving,
635 otherwise the 'doze' mode will be used.
647 the different loglevels.
650 this will be printed to the console
670 the minimum length of time between these messages (in jiffies), by
681 printk_ratelimit_burst specifies the number of messages we can
688 This option can be used to select the type of process address
689 space randomization that is used in the system, for architectures
692 0 - Turn the process address space randomization off. This is the
694 and kernels that are booted with the "norandmaps" parameter.
696 1 - Make the addresses of mmap base, stack and VDSO page randomized.
698 loaded to random addresses. Also for PIE-linked binaries, the
699 location of code start is randomized. This is the default if the
702 2 - Additionally enable heap randomization. This is the default if
707 just after the end of the code+bss. These applications break when
708 start of the brk area is randomized. There are however no known
713 with CONFIG_COMPAT_BRK enabled, which excludes the heap from process
720 ??? This seems to be a way to give an argument to the Sparc
728 The file rtsig-max can be used to tune the maximum number
730 in the system.
732 rtsig-nr shows the number of RT signals currently queued.
738 This file shows the size of the generic SCSI (sg) buffer.
741 the value of SG_BIG_BUFF.
751 This parameter sets the total amount of shared memory pages that
755 If you are not sure what the default PAGE_SIZE is on your Linux
756 system, you can run the following command:
764 This value can be used to query and set the run time limit
765 on the maximum shared memory segment size that can be created.
766 Shared memory segments up to 1Gb are now supported in the
780 from the process. The only use left for IPC_RMID is to immediately
781 destroy an unattached segment. Of course, this breaks the way things are
794 Control how file position affects the behavior of updating sysctl values
795 via the /proc/sys interface:
798 Each write syscall must fully contain the sysctl value to be
799 written, and multiple writes on the same sysctl file descriptor
800 will rewrite the sysctl value, regardless of file position.
802 perform writes to a sysctl file descriptor when the file position
805 will append to the sysctl value buffer. Anything past the max length
806 of the sysctl value buffer will be ignored. Writes to numeric sysctl
807 entries must always be at file position 0 and the value must be
808 fully contained in the buffer sent in the write syscall.
814 This value controls the soft lockup detector thread's behavior
822 0: do nothing. This is the default behavior.
830 This parameter can be used to control the soft lockup detector.
832 0 - disable the soft lockup detector
833 1 - enable the soft lockup detector
835 The soft lockup detector monitors CPUs for threads that are hogging the CPUs
836 without rescheduling voluntarily, and thus prevent the 'watchdog/N' threads
837 from running. The mechanism depends on the CPUs ability to respond to timer
838 interrupts which are needed for the 'watchdog/N' threads to be woken up by
839 the watchdog timer function, otherwise the NMI watchdog - if enabled - can
846 Non-zero if the kernel has been tainted. Numeric values, which
855 8 - A module was forcibly unloaded from the system by rmmod -f.
856 16 - A hardware machine check error occurred on the system.
857 32 - A bad page was discovered on the system.
858 64 - The user has asked that the system be marked "tainted". This
860 the hardware, or for other reasons.
862 256 - The ACPI DSDT has been overridden with one supplied by the user
863 instead of using the one provided by the hardware.
870 16384 - A soft lockup has previously occurred on the system.
877 This value controls the maximum number of threads that can be created
880 During initialization the kernel sets this value such that even if the
881 maximum number of threads is created, the thread structures occupy only
882 a part (1/8th) of the available RAM pages.
885 The maximum value that can be written to threads-max is given by the
890 The value written is checked against the available RAM pages. If the
891 thread structures would occupy too much (more than 1/8th) of the
898 The value in this file affects behavior of handling NMI. When the
903 example. If a system hangs up, try pressing the NMI switch.
909 This parameter can be used to disable or enable the soft lockup detector
910 _and_ the NMI watchdog (i.e. the hard lockup detector) at the same time.
915 The soft lockup detector and the NMI watchdog can also be disabled or
916 enabled individually, using the soft_watchdog and nmi_watchdog parameters.
917 If the watchdog parameter is read, for example by executing
921 the output of this command (0 or 1) shows the logical OR of soft_watchdog
928 This value can be used to control the frequency of hrtimer and NMI
929 events and the soft and hard lockup thresholds. The default threshold