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diff --git a/man5/proc_sys_kernel.5 b/man5/proc_sys_kernel.5 deleted file mode 100644 index 334d3be..0000000 --- a/man5/proc_sys_kernel.5 +++ /dev/null @@ -1,691 +0,0 @@ -.\" Copyright (C) 1994, 1995, Daniel Quinlan <quinlan@yggdrasil.com> -.\" Copyright (C) 2002-2008, 2017, Michael Kerrisk <mtk.manpages@gmail.com> -.\" Copyright (C) , Andries Brouwer <aeb@cwi.nl> -.\" Copyright (C) 2023, Alejandro Colomar <alx@kernel.org> -.\" -.\" SPDX-License-Identifier: GPL-3.0-or-later -.\" -.TH proc_sys_kernel 5 2023-09-30 "Linux man-pages 6.7" -.SH NAME -/proc/sys/kernel/ \- control a range of kernel parameters -.SH DESCRIPTION -.TP -.I /proc/sys/kernel/ -This directory contains files controlling a range of kernel parameters, -as described below. -.TP -.I /proc/sys/kernel/acct -This file -contains three numbers: -.IR highwater , -.IR lowwater , -and -.IR frequency . -If BSD-style process accounting is enabled, these values control -its behavior. -If free space on filesystem where the log lives goes below -.I lowwater -percent, accounting suspends. -If free space gets above -.I highwater -percent, accounting resumes. -.I frequency -determines -how often the kernel checks the amount of free space (value is in -seconds). -Default values are 4, 2, and 30. -That is, suspend accounting if 2% or less space is free; resume it -if 4% or more space is free; consider information about amount of free space -valid for 30 seconds. -.TP -.IR /proc/sys/kernel/auto_msgmni " (Linux 2.6.27 to Linux 3.18)" -.\" commit 9eefe520c814f6f62c5d36a2ddcd3fb99dfdb30e (introduces feature) -.\" commit 0050ee059f7fc86b1df2527aaa14ed5dc72f9973 (rendered redundant) -From Linux 2.6.27 to Linux 3.18, -this file was used to control recomputing of the value in -.I /proc/sys/kernel/msgmni -upon the addition or removal of memory or upon IPC namespace creation/removal. -Echoing "1" into this file enabled -.I msgmni -automatic recomputing (and triggered a recomputation of -.I msgmni -based on the current amount of available memory and number of IPC namespaces). -Echoing "0" disabled automatic recomputing. -(Automatic recomputing was also disabled if a value was explicitly assigned to -.IR /proc/sys/kernel/msgmni .) -The default value in -.I auto_msgmni -was 1. -.IP -Since Linux 3.19, the content of this file has no effect (because -.I msgmni -.\" FIXME Must document the 3.19 'msgmni' changes. -defaults to near the maximum value possible), -and reads from this file always return the value "0". -.TP -.IR /proc/sys/kernel/cap_last_cap " (since Linux 3.2)" -See -.BR capabilities (7). -.TP -.IR /proc/sys/kernel/cap\-bound " (from Linux 2.2 to Linux 2.6.24)" -This file holds the value of the kernel -.I "capability bounding set" -(expressed as a signed decimal number). -This set is ANDed against the capabilities permitted to a process -during -.BR execve (2). -Starting with Linux 2.6.25, -the system-wide capability bounding set disappeared, -and was replaced by a per-thread bounding set; see -.BR capabilities (7). -.TP -.I /proc/sys/kernel/core_pattern -See -.BR core (5). -.TP -.I /proc/sys/kernel/core_pipe_limit -See -.BR core (5). -.TP -.I /proc/sys/kernel/core_uses_pid -See -.BR core (5). -.TP -.I /proc/sys/kernel/ctrl\-alt\-del -This file -controls the handling of Ctrl-Alt-Del from the keyboard. -When the value in this file is 0, Ctrl-Alt-Del is trapped and -sent to the -.BR init (1) -program to handle a graceful restart. -When the value is greater than zero, Linux's reaction to a Vulcan -Nerve Pinch (tm) will be an immediate reboot, without even -syncing its dirty buffers. -Note: when a program (like dosemu) has the keyboard in "raw" -mode, the Ctrl-Alt-Del is intercepted by the program before it -ever reaches the kernel tty layer, and it's up to the program -to decide what to do with it. -.TP -.IR /proc/sys/kernel/dmesg_restrict " (since Linux 2.6.37)" -The value in this file determines who can see kernel syslog contents. -A value of 0 in this file imposes no restrictions. -If the value is 1, only privileged users can read the kernel syslog. -(See -.BR syslog (2) -for more details.) -Since Linux 3.4, -.\" commit 620f6e8e855d6d447688a5f67a4e176944a084e8 -only users with the -.B CAP_SYS_ADMIN -capability may change the value in this file. -.TP -.IR /proc/sys/kernel/domainname " and " /proc/sys/kernel/hostname -can be used to set the NIS/YP domainname and the -hostname of your box in exactly the same way as the commands -.BR domainname (1) -and -.BR hostname (1), -that is: -.IP -.in +4n -.EX -.RB "#" " echo \[aq]darkstar\[aq] > /proc/sys/kernel/hostname" -.RB "#" " echo \[aq]mydomain\[aq] > /proc/sys/kernel/domainname" -.EE -.in -.IP -has the same effect as -.IP -.in +4n -.EX -.RB "#" " hostname \[aq]darkstar\[aq]" -.RB "#" " domainname \[aq]mydomain\[aq]" -.EE -.in -.IP -Note, however, that the classic darkstar.frop.org has the -hostname "darkstar" and DNS (Internet Domain Name Server) -domainname "frop.org", not to be confused with the NIS (Network -Information Service) or YP (Yellow Pages) domainname. -These two -domain names are in general different. -For a detailed discussion -see the -.BR hostname (1) -man page. -.TP -.I /proc/sys/kernel/hotplug -This file -contains the pathname for the hotplug policy agent. -The default value in this file is -.IR /sbin/hotplug . -.TP -.\" Removed in commit 87f504e5c78b910b0c1d6ffb89bc95e492322c84 (tglx/history.git) -.IR /proc/sys/kernel/htab\-reclaim " (before Linux 2.4.9.2)" -(PowerPC only) If this file is set to a nonzero value, -the PowerPC htab -.\" removed in commit 1b483a6a7b2998e9c98ad985d7494b9b725bd228, before Linux 2.6.28 -(see kernel file -.IR Documentation/powerpc/ppc_htab.txt ) -is pruned -each time the system hits the idle loop. -.TP -.I /proc/sys/kernel/keys/ -This directory contains various files that define parameters and limits -for the key-management facility. -These files are described in -.BR keyrings (7). -.TP -.IR /proc/sys/kernel/kptr_restrict " (since Linux 2.6.38)" -.\" 455cd5ab305c90ffc422dd2e0fb634730942b257 -The value in this file determines whether kernel addresses are exposed via -.I /proc -files and other interfaces. -A value of 0 in this file imposes no restrictions. -If the value is 1, kernel pointers printed using the -.I %pK -format specifier will be replaced with zeros unless the user has the -.B CAP_SYSLOG -capability. -If the value is 2, kernel pointers printed using the -.I %pK -format specifier will be replaced with zeros regardless -of the user's capabilities. -The initial default value for this file was 1, -but the default was changed -.\" commit 411f05f123cbd7f8aa1edcae86970755a6e2a9d9 -to 0 in Linux 2.6.39. -Since Linux 3.4, -.\" commit 620f6e8e855d6d447688a5f67a4e176944a084e8 -only users with the -.B CAP_SYS_ADMIN -capability can change the value in this file. -.TP -.I /proc/sys/kernel/l2cr -(PowerPC only) This file -contains a flag that controls the L2 cache of G3 processor -boards. -If 0, the cache is disabled. -Enabled if nonzero. -.TP -.I /proc/sys/kernel/modprobe -This file contains the pathname for the kernel module loader. -The default value is -.IR /sbin/modprobe . -The file is present only if the kernel is built with the -.B CONFIG_MODULES -.RB ( CONFIG_KMOD -in Linux 2.6.26 and earlier) -option enabled. -It is described by the Linux kernel source file -.I Documentation/kmod.txt -(present only in Linux 2.4 and earlier). -.TP -.IR /proc/sys/kernel/modules_disabled " (since Linux 2.6.31)" -.\" 3d43321b7015387cfebbe26436d0e9d299162ea1 -.\" From Documentation/sysctl/kernel.txt -A toggle value indicating if modules are allowed to be loaded -in an otherwise modular kernel. -This toggle defaults to off (0), but can be set true (1). -Once true, modules can be neither loaded nor unloaded, -and the toggle cannot be set back to false. -The file is present only if the kernel is built with the -.B CONFIG_MODULES -option enabled. -.TP -.IR /proc/sys/kernel/msgmax " (since Linux 2.2)" -This file defines -a system-wide limit specifying the maximum number of bytes in -a single message written on a System V message queue. -.TP -.IR /proc/sys/kernel/msgmni " (since Linux 2.4)" -This file defines the system-wide limit on the number of -message queue identifiers. -See also -.IR /proc/sys/kernel/auto_msgmni . -.TP -.IR /proc/sys/kernel/msgmnb " (since Linux 2.2)" -This file defines a system-wide parameter used to initialize the -.I msg_qbytes -setting for subsequently created message queues. -The -.I msg_qbytes -setting specifies the maximum number of bytes that may be written to the -message queue. -.TP -.IR /proc/sys/kernel/ngroups_max " (since Linux 2.6.4)" -This is a read-only file that displays the upper limit on the -number of a process's group memberships. -.TP -.IR /proc/sys/kernel/ns_last_pid " (since Linux 3.3)" -See -.BR pid_namespaces (7). -.TP -.IR /proc/sys/kernel/ostype " and " /proc/sys/kernel/osrelease -These files -give substrings of -.IR /proc/version . -.TP -.IR /proc/sys/kernel/overflowgid " and " /proc/sys/kernel/overflowuid -These files duplicate the files -.I /proc/sys/fs/overflowgid -and -.IR /proc/sys/fs/overflowuid . -.TP -.I /proc/sys/kernel/panic -This file gives read/write access to the kernel variable -.IR panic_timeout . -If this is zero, the kernel will loop on a panic; if nonzero, -it indicates that the kernel should autoreboot after this number -of seconds. -When you use the -software watchdog device driver, the recommended setting is 60. -.TP -.IR /proc/sys/kernel/panic_on_oops " (since Linux 2.5.68)" -This file controls the kernel's behavior when an oops -or BUG is encountered. -If this file contains 0, then the system -tries to continue operation. -If it contains 1, then the system -delays a few seconds (to give klogd time to record the oops output) -and then panics. -If the -.I /proc/sys/kernel/panic -file is also nonzero, then the machine will be rebooted. -.TP -.IR /proc/sys/kernel/pid_max " (since Linux 2.5.34)" -This file specifies the value at which PIDs wrap around -(i.e., the value in this file is one greater than the maximum PID). -PIDs greater than this value are not allocated; -thus, the value in this file also acts as a system-wide limit -on the total number of processes and threads. -The default value for this file, 32768, -results in the same range of PIDs as on earlier kernels. -On 32-bit platforms, 32768 is the maximum value for -.IR pid_max . -On 64-bit systems, -.I pid_max -can be set to any value up to 2\[ha]22 -.RB ( PID_MAX_LIMIT , -approximately 4 million). -.\" Prior to Linux 2.6.10, pid_max could also be raised above 32768 on 32-bit -.\" platforms, but this broke /proc/[pid] -.\" See http://marc.theaimsgroup.com/?l=linux-kernel&m=109513010926152&w=2 -.TP -.IR /proc/sys/kernel/powersave\-nap " (PowerPC only)" -This file contains a flag. -If set, Linux-PPC will use the "nap" mode of -powersaving, -otherwise the "doze" mode will be used. -.TP -.I /proc/sys/kernel/printk -See -.BR syslog (2). -.TP -.IR /proc/sys/kernel/pty " (since Linux 2.6.4)" -This directory contains two files relating to the number of UNIX 98 -pseudoterminals (see -.BR pts (4)) -on the system. -.TP -.I /proc/sys/kernel/pty/max -This file defines the maximum number of pseudoterminals. -.\" FIXME Document /proc/sys/kernel/pty/reserve -.\" New in Linux 3.3 -.\" commit e9aba5158a80098447ff207a452a3418ae7ee386 -.TP -.I /proc/sys/kernel/pty/nr -This read-only file -indicates how many pseudoterminals are currently in use. -.TP -.I /proc/sys/kernel/random/ -This directory -contains various parameters controlling the operation of the file -.IR /dev/random . -See -.BR random (4) -for further information. -.TP -.IR /proc/sys/kernel/random/uuid " (since Linux 2.4)" -Each read from this read-only file returns a randomly generated 128-bit UUID, -as a string in the standard UUID format. -.TP -.IR /proc/sys/kernel/randomize_va_space " (since Linux 2.6.12)" -.\" Some further details can be found in Documentation/sysctl/kernel.txt -Select the address space layout randomization (ASLR) policy for the system -(on architectures that support ASLR). -Three values are supported for this file: -.RS -.TP -.B 0 -Turn ASLR off. -This is the default for architectures that don't support ASLR, -and when the kernel is booted with the -.I norandmaps -parameter. -.TP -.B 1 -Make the addresses of -.BR mmap (2) -allocations, the stack, and the VDSO page randomized. -Among other things, this means that shared libraries will be -loaded at randomized addresses. -The text segment of PIE-linked binaries will also be loaded -at a randomized address. -This value is the default if the kernel was configured with -.BR CONFIG_COMPAT_BRK . -.TP -.B 2 -(Since Linux 2.6.25) -.\" commit c1d171a002942ea2d93b4fbd0c9583c56fce0772 -Also support heap randomization. -This value is the default if the kernel was not configured with -.BR CONFIG_COMPAT_BRK . -.RE -.TP -.I /proc/sys/kernel/real\-root\-dev -This file is documented in the Linux kernel source file -.I Documentation/admin\-guide/initrd.rst -.\" commit 9d85025b0418163fae079c9ba8f8445212de8568 -(or -.I Documentation/initrd.txt -before Linux 4.10). -.TP -.IR /proc/sys/kernel/reboot\-cmd " (Sparc only)" -This file seems to be a way to give an argument to the SPARC -ROM/Flash boot loader. -Maybe to tell it what to do after -rebooting? -.TP -.I /proc/sys/kernel/rtsig\-max -(Up to and including Linux 2.6.7; see -.BR setrlimit (2)) -This file can be used to tune the maximum number -of POSIX real-time (queued) signals that can be outstanding -in the system. -.TP -.I /proc/sys/kernel/rtsig\-nr -(Up to and including Linux 2.6.7.) -This file shows the number of POSIX real-time signals currently queued. -.TP -.IR /proc/ pid /sched_autogroup_enabled " (since Linux 2.6.38)" -.\" commit 5091faa449ee0b7d73bc296a93bca9540fc51d0a -See -.BR sched (7). -.TP -.IR /proc/sys/kernel/sched_child_runs_first " (since Linux 2.6.23)" -If this file contains the value zero, then, after a -.BR fork (2), -the parent is first scheduled on the CPU. -If the file contains a nonzero value, -then the child is scheduled first on the CPU. -(Of course, on a multiprocessor system, -the parent and the child might both immediately be scheduled on a CPU.) -.TP -.IR /proc/sys/kernel/sched_rr_timeslice_ms " (since Linux 3.9)" -See -.BR sched_rr_get_interval (2). -.TP -.IR /proc/sys/kernel/sched_rt_period_us " (since Linux 2.6.25)" -See -.BR sched (7). -.TP -.IR /proc/sys/kernel/sched_rt_runtime_us " (since Linux 2.6.25)" -See -.BR sched (7). -.TP -.IR /proc/sys/kernel/seccomp/ " (since Linux 4.14)" -.\" commit 8e5f1ad116df6b0de65eac458d5e7c318d1c05af -This directory provides additional seccomp information and -configuration. -See -.BR seccomp (2) -for further details. -.TP -.IR /proc/sys/kernel/sem " (since Linux 2.4)" -This file contains 4 numbers defining limits for System V IPC semaphores. -These fields are, in order: -.RS -.TP -SEMMSL -The maximum semaphores per semaphore set. -.TP -SEMMNS -A system-wide limit on the number of semaphores in all semaphore sets. -.TP -SEMOPM -The maximum number of operations that may be specified in a -.BR semop (2) -call. -.TP -SEMMNI -A system-wide limit on the maximum number of semaphore identifiers. -.RE -.TP -.I /proc/sys/kernel/sg\-big\-buff -This file -shows the size of the generic SCSI device (sg) buffer. -You can't tune it just yet, but you could change it at -compile time by editing -.I include/scsi/sg.h -and changing -the value of -.BR SG_BIG_BUFF . -However, there shouldn't be any reason to change this value. -.TP -.IR /proc/sys/kernel/shm_rmid_forced " (since Linux 3.1)" -.\" commit b34a6b1da371ed8af1221459a18c67970f7e3d53 -.\" See also Documentation/sysctl/kernel.txt -If this file is set to 1, all System V shared memory segments will -be marked for destruction as soon as the number of attached processes -falls to zero; -in other words, it is no longer possible to create shared memory segments -that exist independently of any attached process. -.IP -The effect is as though a -.BR shmctl (2) -.B IPC_RMID -is performed on all existing segments as well as all segments -created in the future (until this file is reset to 0). -Note that existing segments that are attached to no process will be -immediately destroyed when this file is set to 1. -Setting this option will also destroy segments that were created, -but never attached, -upon termination of the process that created the segment with -.BR shmget (2). -.IP -Setting this file to 1 provides a way of ensuring that -all System V shared memory segments are counted against the -resource usage and resource limits (see the description of -.B RLIMIT_AS -in -.BR getrlimit (2)) -of at least one process. -.IP -Because setting this file to 1 produces behavior that is nonstandard -and could also break existing applications, -the default value in this file is 0. -Set this file to 1 only if you have a good understanding -of the semantics of the applications using -System V shared memory on your system. -.TP -.IR /proc/sys/kernel/shmall " (since Linux 2.2)" -This file -contains the system-wide limit on the total number of pages of -System V shared memory. -.TP -.IR /proc/sys/kernel/shmmax " (since Linux 2.2)" -This file -can be used to query and set the run-time limit -on the maximum (System V IPC) shared memory segment size that can be -created. -Shared memory segments up to 1 GB are now supported in the -kernel. -This value defaults to -.BR SHMMAX . -.TP -.IR /proc/sys/kernel/shmmni " (since Linux 2.4)" -This file -specifies the system-wide maximum number of System V shared memory -segments that can be created. -.TP -.IR /proc/sys/kernel/sysctl_writes_strict " (since Linux 3.16)" -.\" commit f88083005ab319abba5d0b2e4e997558245493c8 -.\" commit 2ca9bb456ada8bcbdc8f77f8fc78207653bbaa92 -.\" commit f4aacea2f5d1a5f7e3154e967d70cf3f711bcd61 -.\" commit 24fe831c17ab8149413874f2fd4e5c8a41fcd294 -The value in this file determines how the file offset affects -the behavior of updating entries in files under -.IR /proc/sys . -The file has three possible values: -.RS -.TP 4 -\-1 -This provides legacy handling, with no printk warnings. -Each -.BR write (2) -must fully contain the value to be written, -and multiple writes on the same file descriptor -will overwrite the entire value, regardless of the file position. -.TP -0 -(default) This provides the same behavior as for \-1, -but printk warnings are written for processes that -perform writes when the file offset is not 0. -.TP -1 -Respect the file offset when writing strings into -.I /proc/sys -files. -Multiple writes will -.I append -to the value buffer. -Anything written beyond the maximum length -of the value buffer will be ignored. -Writes to numeric -.I /proc/sys -entries must always be at file offset 0 and the value must be -fully contained in the buffer provided to -.BR write (2). -.\" FIXME . -.\" With /proc/sys/kernel/sysctl_writes_strict==1, writes at an -.\" offset other than 0 do not generate an error. Instead, the -.\" write() succeeds, but the file is left unmodified. -.\" This is surprising. The behavior may change in the future. -.\" See thread.gmane.org/gmane.linux.man/9197 -.\" From: Michael Kerrisk (man-pages <mtk.manpages@...> -.\" Subject: sysctl_writes_strict documentation + an oddity? -.\" Newsgroups: gmane.linux.man, gmane.linux.kernel -.\" Date: 2015-05-09 08:54:11 GMT -.RE -.TP -.I /proc/sys/kernel/sysrq -This file controls the functions allowed to be invoked by the SysRq key. -By default, -the file contains 1 meaning that every possible SysRq request is allowed -(in older kernel 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). -Possible values in this file are: -.RS -.TP 5 -0 -Disable sysrq completely -.TP -1 -Enable all functions of sysrq -.TP -> 1 -Bit mask of allowed sysrq functions, as follows: -.PD 0 -.RS -.TP 5 -\ \ 2 -Enable control of console logging level -.TP -\ \ 4 -Enable control of keyboard (SAK, unraw) -.TP -\ \ 8 -Enable debugging dumps of processes etc. -.TP -\ 16 -Enable sync command -.TP -\ 32 -Enable remount read-only -.TP -\ 64 -Enable signaling of processes (term, kill, oom-kill) -.TP -128 -Allow reboot/poweroff -.TP -256 -Allow nicing of all real-time tasks -.RE -.PD -.RE -.IP -This file is present only if the -.B CONFIG_MAGIC_SYSRQ -kernel configuration option is enabled. -For further details see the Linux kernel source file -.I Documentation/admin\-guide/sysrq.rst -.\" commit 9d85025b0418163fae079c9ba8f8445212de8568 -(or -.I Documentation/sysrq.txt -before Linux 4.10). -.TP -.I /proc/sys/kernel/version -This file contains a string such as: -.IP -.in +4n -.EX -#5 Wed Feb 25 21:49:24 MET 1998 -.EE -.in -.IP -The "#5" means that -this is the fifth kernel built from this source base and the -date following it indicates the time the kernel was built. -.TP -.IR /proc/sys/kernel/threads\-max " (since Linux 2.3.11)" -.\" The following is based on Documentation/sysctl/kernel.txt -This file specifies the system-wide limit on the number of -threads (tasks) that can be created on the system. -.IP -Since Linux 4.1, -.\" commit 230633d109e35b0a24277498e773edeb79b4a331 -the value that can be written to -.I threads\-max -is bounded. -The minimum value that can be written is 20. -The maximum value that can be written is given by the -constant -.B FUTEX_TID_MASK -(0x3fffffff). -If a value outside of this range is written to -.IR threads\-max , -the error -.B EINVAL -occurs. -.IP -The value written is checked against the available RAM pages. -If the thread structures would occupy too much (more than 1/8th) -of the available RAM pages, -.I threads\-max -is reduced accordingly. -.TP -.IR /proc/sys/kernel/yama/ptrace_scope " (since Linux 3.5)" -See -.BR ptrace (2). -.TP -.IR /proc/sys/kernel/zero\-paged " (PowerPC only)" -This file -contains a flag. -When enabled (nonzero), Linux-PPC will pre-zero pages in -the idle loop, possibly speeding up get_free_pages. -.SH SEE ALSO -.BR proc (5), -.BR proc_sys (5) |