diff options
Diffstat (limited to 'Documentation/admin-guide')
| -rw-r--r-- | Documentation/admin-guide/binfmt-misc.rst | 4 | ||||
| -rw-r--r-- | Documentation/admin-guide/blockdev/zram.rst | 2 | ||||
| -rw-r--r-- | Documentation/admin-guide/bootconfig.rst | 2 | ||||
| -rw-r--r-- | Documentation/admin-guide/cgroup-v1/index.rst | 2 | ||||
| -rw-r--r-- | Documentation/admin-guide/cgroup-v2.rst | 28 | ||||
| -rw-r--r-- | Documentation/admin-guide/edid.rst | 60 | ||||
| -rw-r--r-- | Documentation/admin-guide/hw-vuln/tsx_async_abort.rst | 2 | ||||
| -rw-r--r-- | Documentation/admin-guide/index.rst | 1 | ||||
| -rw-r--r-- | Documentation/admin-guide/kernel-parameters.txt | 26 | ||||
| -rw-r--r-- | Documentation/admin-guide/kernel-per-CPU-kthreads.rst | 2 | ||||
| -rw-r--r-- | Documentation/admin-guide/perf/imx-ddr.rst | 3 | ||||
| -rw-r--r-- | Documentation/admin-guide/sysctl/kernel.rst | 1049 |
12 files changed, 640 insertions, 541 deletions
diff --git a/Documentation/admin-guide/binfmt-misc.rst b/Documentation/admin-guide/binfmt-misc.rst index 97b0d7927078..95c93bbe408a 100644 --- a/Documentation/admin-guide/binfmt-misc.rst +++ b/Documentation/admin-guide/binfmt-misc.rst @@ -1,5 +1,5 @@ -Kernel Support for miscellaneous (your favourite) Binary Formats v1.1 -===================================================================== +Kernel Support for miscellaneous Binary Formats (binfmt_misc) +============================================================= This Kernel feature allows you to invoke almost (for restrictions see below) every program by simply typing its name in the shell. diff --git a/Documentation/admin-guide/blockdev/zram.rst b/Documentation/admin-guide/blockdev/zram.rst index 27c77d853028..a6fd1f9b5faf 100644 --- a/Documentation/admin-guide/blockdev/zram.rst +++ b/Documentation/admin-guide/blockdev/zram.rst @@ -251,8 +251,6 @@ line of text and contains the following stats separated by whitespace: ================ ============================================================= orig_data_size uncompressed size of data stored in this disk. - This excludes same-element-filled pages (same_pages) since - no memory is allocated for them. Unit: bytes compr_data_size compressed size of data stored in this disk mem_used_total the amount of memory allocated for this disk. This diff --git a/Documentation/admin-guide/bootconfig.rst b/Documentation/admin-guide/bootconfig.rst index cf2edcd09183..d6b3b77a4129 100644 --- a/Documentation/admin-guide/bootconfig.rst +++ b/Documentation/admin-guide/bootconfig.rst @@ -23,7 +23,7 @@ of dot-connected-words, and key and value are connected by ``=``. The value has to be terminated by semi-colon (``;``) or newline (``\n``). For array value, array entries are separated by comma (``,``). :: -KEY[.WORD[...]] = VALUE[, VALUE2[...]][;] + KEY[.WORD[...]] = VALUE[, VALUE2[...]][;] Unlike the kernel command line syntax, spaces are OK around the comma and ``=``. diff --git a/Documentation/admin-guide/cgroup-v1/index.rst b/Documentation/admin-guide/cgroup-v1/index.rst index 10bf48bae0b0..226f64473e8e 100644 --- a/Documentation/admin-guide/cgroup-v1/index.rst +++ b/Documentation/admin-guide/cgroup-v1/index.rst @@ -1,3 +1,5 @@ +.. _cgroup-v1: + ======================== Control Groups version 1 ======================== diff --git a/Documentation/admin-guide/cgroup-v2.rst b/Documentation/admin-guide/cgroup-v2.rst index 3f801461f0f3..fbb111616705 100644 --- a/Documentation/admin-guide/cgroup-v2.rst +++ b/Documentation/admin-guide/cgroup-v2.rst @@ -9,7 +9,7 @@ This is the authoritative documentation on the design, interface and conventions of cgroup v2. It describes all userland-visible aspects of cgroup including core and specific controller behaviors. All future changes must be reflected in this document. Documentation for -v1 is available under Documentation/admin-guide/cgroup-v1/. +v1 is available under :ref:`Documentation/admin-guide/cgroup-v1/index.rst <cgroup-v1>`. .. CONTENTS @@ -1023,7 +1023,7 @@ All time durations are in microseconds. A read-only nested-key file which exists on non-root cgroups. Shows pressure stall information for CPU. See - Documentation/accounting/psi.rst for details. + :ref:`Documentation/accounting/psi.rst <psi>` for details. cpu.uclamp.min A read-write single value file which exists on non-root cgroups. @@ -1103,7 +1103,7 @@ PAGE_SIZE multiple when read back. proportionally to the overage, reducing reclaim pressure for smaller overages. - Effective min boundary is limited by memory.min values of + Effective min boundary is limited by memory.min values of all ancestor cgroups. If there is memory.min overcommitment (child cgroup or cgroups are requiring more protected memory than parent will allow), then each child cgroup will get @@ -1313,53 +1313,41 @@ PAGE_SIZE multiple when read back. Number of major page faults incurred workingset_refault - Number of refaults of previously evicted pages workingset_activate - Number of refaulted pages that were immediately activated workingset_nodereclaim - Number of times a shadow node has been reclaimed pgrefill - Amount of scanned pages (in an active LRU list) pgscan - Amount of scanned pages (in an inactive LRU list) pgsteal - Amount of reclaimed pages pgactivate - Amount of pages moved to the active LRU list pgdeactivate - Amount of pages moved to the inactive LRU list pglazyfree - Amount of pages postponed to be freed under memory pressure pglazyfreed - Amount of reclaimed lazyfree pages thp_fault_alloc - Number of transparent hugepages which were allocated to satisfy a page fault, including COW faults. This counter is not present when CONFIG_TRANSPARENT_HUGEPAGE is not set. thp_collapse_alloc - Number of transparent hugepages which were allocated to allow collapsing an existing range of pages. This counter is not present when CONFIG_TRANSPARENT_HUGEPAGE is not set. @@ -1403,7 +1391,7 @@ PAGE_SIZE multiple when read back. A read-only nested-key file which exists on non-root cgroups. Shows pressure stall information for memory. See - Documentation/accounting/psi.rst for details. + :ref:`Documentation/accounting/psi.rst <psi>` for details. Usage Guidelines @@ -1478,7 +1466,7 @@ IO Interface Files dios Number of discard IOs ====== ===================== - An example read output follows: + An example read output follows:: 8:16 rbytes=1459200 wbytes=314773504 rios=192 wios=353 dbytes=0 dios=0 8:0 rbytes=90430464 wbytes=299008000 rios=8950 wios=1252 dbytes=50331648 dios=3021 @@ -1643,7 +1631,7 @@ IO Interface Files A read-only nested-key file which exists on non-root cgroups. Shows pressure stall information for IO. See - Documentation/accounting/psi.rst for details. + :ref:`Documentation/accounting/psi.rst <psi>` for details. Writeback @@ -1853,7 +1841,7 @@ Cpuset Interface Files from the requested CPUs. The CPU numbers are comma-separated numbers or ranges. - For example: + For example:: # cat cpuset.cpus 0-4,6,8-10 @@ -1892,7 +1880,7 @@ Cpuset Interface Files from the requested memory nodes. The memory node numbers are comma-separated numbers or ranges. - For example: + For example:: # cat cpuset.mems 0-1,3 diff --git a/Documentation/admin-guide/edid.rst b/Documentation/admin-guide/edid.rst new file mode 100644 index 000000000000..80deeb21a265 --- /dev/null +++ b/Documentation/admin-guide/edid.rst @@ -0,0 +1,60 @@ +.. SPDX-License-Identifier: GPL-2.0 + +==== +EDID +==== + +In the good old days when graphics parameters were configured explicitly +in a file called xorg.conf, even broken hardware could be managed. + +Today, with the advent of Kernel Mode Setting, a graphics board is +either correctly working because all components follow the standards - +or the computer is unusable, because the screen remains dark after +booting or it displays the wrong area. Cases when this happens are: + +- The graphics board does not recognize the monitor. +- The graphics board is unable to detect any EDID data. +- The graphics board incorrectly forwards EDID data to the driver. +- The monitor sends no or bogus EDID data. +- A KVM sends its own EDID data instead of querying the connected monitor. + +Adding the kernel parameter "nomodeset" helps in most cases, but causes +restrictions later on. + +As a remedy for such situations, the kernel configuration item +CONFIG_DRM_LOAD_EDID_FIRMWARE was introduced. It allows to provide an +individually prepared or corrected EDID data set in the /lib/firmware +directory from where it is loaded via the firmware interface. The code +(see drivers/gpu/drm/drm_edid_load.c) contains built-in data sets for +commonly used screen resolutions (800x600, 1024x768, 1280x1024, 1600x1200, +1680x1050, 1920x1080) as binary blobs, but the kernel source tree does +not contain code to create these data. In order to elucidate the origin +of the built-in binary EDID blobs and to facilitate the creation of +individual data for a specific misbehaving monitor, commented sources +and a Makefile environment are given here. + +To create binary EDID and C source code files from the existing data +material, simply type "make" in tools/edid/. + +If you want to create your own EDID file, copy the file 1024x768.S, +replace the settings with your own data and add a new target to the +Makefile. Please note that the EDID data structure expects the timing +values in a different way as compared to the standard X11 format. + +X11: + HTimings: + hdisp hsyncstart hsyncend htotal + VTimings: + vdisp vsyncstart vsyncend vtotal + +EDID:: + + #define XPIX hdisp + #define XBLANK htotal-hdisp + #define XOFFSET hsyncstart-hdisp + #define XPULSE hsyncend-hsyncstart + + #define YPIX vdisp + #define YBLANK vtotal-vdisp + #define YOFFSET vsyncstart-vdisp + #define YPULSE vsyncend-vsyncstart diff --git a/Documentation/admin-guide/hw-vuln/tsx_async_abort.rst b/Documentation/admin-guide/hw-vuln/tsx_async_abort.rst index af6865b822d2..68d96f0e9c95 100644 --- a/Documentation/admin-guide/hw-vuln/tsx_async_abort.rst +++ b/Documentation/admin-guide/hw-vuln/tsx_async_abort.rst @@ -136,8 +136,6 @@ enables the mitigation by default. The mitigation can be controlled at boot time via a kernel command line option. See :ref:`taa_mitigation_control_command_line`. -.. _virt_mechanism: - Virtualization mitigation ^^^^^^^^^^^^^^^^^^^^^^^^^ diff --git a/Documentation/admin-guide/index.rst b/Documentation/admin-guide/index.rst index f1d0ccffbe72..5a6269fb8593 100644 --- a/Documentation/admin-guide/index.rst +++ b/Documentation/admin-guide/index.rst @@ -75,6 +75,7 @@ configure specific aspects of kernel behavior to your liking. cputopology dell_rbu device-mapper/index + edid efi-stub ext4 nfs/index diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index c07815d230bc..d7da466fd5c3 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -1099,6 +1099,12 @@ A valid base address must be provided, and the serial port must already be setup and configured. + ec_imx21,<addr> + ec_imx6q,<addr> + Start an early, polled-mode, output-only console on the + Freescale i.MX UART at the specified address. The UART + must already be setup and configured. + ar3700_uart,<addr> Start an early, polled-mode console on the Armada 3700 serial port at the specified @@ -1779,7 +1785,7 @@ provided by tboot because it makes the system vulnerable to DMA attacks. nobounce [Default off] - Disable bounce buffer for unstrusted devices such as + Disable bounce buffer for untrusted devices such as the Thunderbolt devices. This will treat the untrusted devices as the trusted ones, hence might expose security risks of DMA attacks. @@ -1883,7 +1889,7 @@ No delay ip= [IP_PNP] - See Documentation/filesystems/nfs/nfsroot.txt. + See Documentation/admin-guide/nfs/nfsroot.rst. ipcmni_extend [KNL] Extend the maximum number of unique System V IPC identifiers from 32,768 to 16,777,216. @@ -2795,7 +2801,7 @@ <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>] mtdparts= [MTD] - See drivers/mtd/cmdlinepart.c. + See drivers/mtd/parsers/cmdlinepart.c multitce=off [PPC] This parameter disables the use of the pSeries firmware feature for updating multiple TCE entries @@ -2853,13 +2859,13 @@ Default value is 0. nfsaddrs= [NFS] Deprecated. Use ip= instead. - See Documentation/filesystems/nfs/nfsroot.txt. + See Documentation/admin-guide/nfs/nfsroot.rst. nfsroot= [NFS] nfs root filesystem for disk-less boxes. - See Documentation/filesystems/nfs/nfsroot.txt. + See Documentation/admin-guide/nfs/nfsroot.rst. nfsrootdebug [NFS] enable nfsroot debugging messages. - See Documentation/filesystems/nfs/nfsroot.txt. + See Documentation/admin-guide/nfs/nfsroot.rst. nfs.callback_nr_threads= [NFSv4] set the total number of threads that the @@ -4514,10 +4520,10 @@ Format: <integer> A nonzero value instructs the soft-lockup detector - to panic the machine when a soft-lockup occurs. This - is also controlled by CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC - which is the respective build-time switch to that - functionality. + to panic the machine when a soft-lockup occurs. It is + also controlled by the kernel.softlockup_panic sysctl + and CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC, which is the + respective build-time switch to that functionality. softlockup_all_cpu_backtrace= [KNL] Should the soft-lockup detector generate diff --git a/Documentation/admin-guide/kernel-per-CPU-kthreads.rst b/Documentation/admin-guide/kernel-per-CPU-kthreads.rst index baeeba8762ae..21818aca4708 100644 --- a/Documentation/admin-guide/kernel-per-CPU-kthreads.rst +++ b/Documentation/admin-guide/kernel-per-CPU-kthreads.rst @@ -234,7 +234,7 @@ To reduce its OS jitter, do any of the following: Such a workqueue can be confined to a given subset of the CPUs using the ``/sys/devices/virtual/workqueue/*/cpumask`` sysfs files. The set of WQ_SYSFS workqueues can be displayed using - "ls sys/devices/virtual/workqueue". That said, the workqueues + "ls /sys/devices/virtual/workqueue". That said, the workqueues maintainer would like to caution people against indiscriminately sprinkling WQ_SYSFS across all the workqueues. The reason for caution is that it is easy to add WQ_SYSFS, but because sysfs is diff --git a/Documentation/admin-guide/perf/imx-ddr.rst b/Documentation/admin-guide/perf/imx-ddr.rst index 3726a10a03ba..f05f56c73b7d 100644 --- a/Documentation/admin-guide/perf/imx-ddr.rst +++ b/Documentation/admin-guide/perf/imx-ddr.rst @@ -43,7 +43,8 @@ value 1 for supported. AXI_ID and AXI_MASKING are mapped on DPCR1 register in performance counter. When non-masked bits are matching corresponding AXI_ID bits then counter is - incremented. Perf counter is incremented if + incremented. Perf counter is incremented if:: + AxID && AXI_MASKING == AXI_ID && AXI_MASKING This filter doesn't support filter different AXI ID for axid-read and axid-write diff --git a/Documentation/admin-guide/sysctl/kernel.rst b/Documentation/admin-guide/sysctl/kernel.rst index def074807cee..335696d3360d 100644 --- a/Documentation/admin-guide/sysctl/kernel.rst +++ b/Documentation/admin-guide/sysctl/kernel.rst @@ -2,262 +2,197 @@ Documentation for /proc/sys/kernel/ =================================== -kernel version 2.2.10 +.. See scripts/check-sysctl-docs to keep this up to date + Copyright (c) 1998, 1999, Rik van Riel <riel@nl.linux.org> Copyright (c) 2009, Shen Feng<shen@cn.fujitsu.com> -For general info and legal blurb, please look in index.rst. +For general info and legal blurb, please look in :doc:`index`. ------------------------------------------------------------------------------ This file contains documentation for the sysctl files in -/proc/sys/kernel/ and is valid for Linux kernel version 2.2. +``/proc/sys/kernel/`` and is valid for Linux kernel version 2.2. The files in this directory can be used to tune and monitor miscellaneous and general things in the operation of the Linux -kernel. Since some of the files _can_ be used to screw up your +kernel. Since some of the files *can* be used to screw up your system, it is advisable to read both documentation and source before actually making adjustments. Currently, these files might (depending on your configuration) -show up in /proc/sys/kernel: - -- acct -- acpi_video_flags -- auto_msgmni -- bootloader_type [ X86 only ] -- bootloader_version [ X86 only ] -- cap_last_cap -- core_pattern -- core_pipe_limit -- core_uses_pid -- ctrl-alt-del -- dmesg_restrict -- domainname -- hostname -- hotplug -- hardlockup_all_cpu_backtrace -- hardlockup_panic -- hung_task_panic -- hung_task_check_count -- hung_task_timeout_secs -- hung_task_check_interval_secs -- hung_task_warnings -- hyperv_record_panic_msg -- kexec_load_disabled -- kptr_restrict -- l2cr [ PPC only ] -- modprobe ==> Documentation/debugging-modules.txt -- modules_disabled -- msg_next_id [ sysv ipc ] -- msgmax -- msgmnb -- msgmni -- nmi_watchdog -- osrelease -- ostype -- overflowgid -- overflowuid -- panic -- panic_on_oops -- panic_on_stackoverflow -- panic_on_unrecovered_nmi -- panic_on_warn -- panic_print -- panic_on_rcu_stall -- perf_cpu_time_max_percent -- perf_event_paranoid -- perf_event_max_stack -- perf_event_mlock_kb -- perf_event_max_contexts_per_stack -- pid_max -- powersave-nap [ PPC only ] -- printk -- printk_delay -- printk_ratelimit -- printk_ratelimit_burst -- pty ==> Documentation/filesystems/devpts.txt -- randomize_va_space -- real-root-dev ==> Documentation/admin-guide/initrd.rst -- reboot-cmd [ SPARC only ] -- rtsig-max -- rtsig-nr -- sched_energy_aware -- seccomp/ ==> Documentation/userspace-api/seccomp_filter.rst -- sem -- sem_next_id [ sysv ipc ] -- sg-big-buff [ generic SCSI device (sg) ] -- shm_next_id [ sysv ipc ] -- shm_rmid_forced -- shmall -- shmmax [ sysv ipc ] -- shmmni -- softlockup_all_cpu_backtrace -- soft_watchdog -- stack_erasing -- stop-a [ SPARC only ] -- sysrq ==> Documentation/admin-guide/sysrq.rst -- sysctl_writes_strict -- tainted ==> Documentation/admin-guide/tainted-kernels.rst -- threads-max -- unknown_nmi_panic -- watchdog -- watchdog_thresh -- version - - -acct: -===== +show up in ``/proc/sys/kernel``: + +.. contents:: :local: + + +acct +==== + +:: -highwater lowwater frequency + highwater lowwater frequency If BSD-style process accounting is enabled these values control its behaviour. If free space on filesystem where the log lives -goes below <lowwater>% accounting suspends. If free space gets -above <highwater>% accounting resumes. <Frequency> determines +goes below ``lowwater``% accounting suspends. If free space gets +above ``highwater``% accounting resumes. ``frequency`` determines how often do we check the amount of free space (value is in seconds). Default: -4 2 30 -That is, suspend accounting if there left <= 2% free; resume it -if we got >=4%; consider information about amount of free space -valid for 30 seconds. +:: -acpi_video_flags: -================= + 4 2 30 + +That is, suspend accounting if free space drops below 2%; resume it +if it increases to at least 4%; consider information about amount of +free space valid for 30 seconds. -flags -See Doc*/kernel/power/video.txt, it allows mode of video boot to be -set during run time. +acpi_video_flags +================ +See :doc:`/power/video`. This allows the video resume mode to be set, +in a similar fashion to the ``acpi_sleep`` kernel parameter, by +combining the following values: + += ======= +1 s3_bios +2 s3_mode +4 s3_beep += ======= -auto_msgmni: -============ + +auto_msgmni +=========== This variable has no effect and may be removed in future kernel releases. Reading it always returns 0. -Up to Linux 3.17, it enabled/disabled automatic recomputing of msgmni -upon memory add/remove or upon ipc namespace creation/removal. +Up to Linux 3.17, it enabled/disabled automatic recomputing of +`msgmni`_ +upon memory add/remove or upon IPC namespace creation/removal. Echoing "1" into this file enabled msgmni automatic recomputing. -Echoing "0" turned it off. auto_msgmni default value was 1. - +Echoing "0" turned it off. The default value was 1. -bootloader_type: -================ -x86 bootloader identification +bootloader_type (x86 only) +========================== This gives the bootloader type number as indicated by the bootloader, shifted left by 4, and OR'd with the low four bits of the bootloader version. The reason for this encoding is that this used to match the -type_of_loader field in the kernel header; the encoding is kept for +``type_of_loader`` field in the kernel header; the encoding is kept for backwards compatibility. That is, if the full bootloader type number is 0x15 and the full version number is 0x234, this file will contain the value 340 = 0x154. -See the type_of_loader and ext_loader_type fields in -Documentation/x86/boot.rst for additional information. - +See the ``type_of_loader`` and ``ext_loader_type`` fields in +:doc:`/x86/boot` for additional information. -bootloader_version: -=================== -x86 bootloader version +bootloader_version (x86 only) +============================= The complete bootloader version number. In the example above, this file will contain the value 564 = 0x234. -See the type_of_loader and ext_loader_ver fields in -Documentation/x86/boot.rst for additional information. +See the ``type_of_loader`` and ``ext_loader_ver`` fields in +:doc:`/x86/boot` for additional information. -cap_last_cap: -============= +cap_last_cap +============ Highest valid capability of the running kernel. Exports -CAP_LAST_CAP from the kernel. +``CAP_LAST_CAP`` from the kernel. -core_pattern: -============= +core_pattern +============ -core_pattern is used to specify a core dumpfile pattern name. +``core_pattern`` is used to specify a core dumpfile pattern name. * max length 127 characters; default value is "core" -* core_pattern is used as a pattern template for the output filename; - certain string patterns (beginning with '%') are substituted with - their actual values. -* backward compatibility with core_uses_pid: +* ``core_pattern`` is used as a pattern template for the output + filename; certain string patterns (beginning with '%') are + substituted with their actual values. +* backward compatibility with ``core_uses_pid``: - If core_pattern does not include "%p" (default does not) - and core_uses_pid is set, then .PID will be appended to + If ``core_pattern`` does not include "%p" (default does not) + and ``core_uses_pid`` is set, then .PID will be appended to the filename. -* corename format specifiers:: - - %<NUL> '%' is dropped - %% output one '%' - %p pid - %P global pid (init PID namespace) - %i tid - %I global tid (init PID namespace) - %u uid (in initial user namespace) - %g gid (in initial user namespace) - %d dump mode, matches PR_SET_DUMPABLE and - /proc/sys/fs/suid_dumpable - %s signal number - %t UNIX time of dump - %h hostname - %e executable filename (may be shortened) - %E executable path - %<OTHER> both are dropped +* corename format specifiers + + ======== ========================================== + %<NUL> '%' is dropped + %% output one '%' + %p pid + %P global pid (init PID namespace) + %i tid + %I global tid (init PID namespace) + %u uid (in initial user namespace) + %g gid (in initial user namespace) + %d dump mode, matches ``PR_SET_DUMPABLE`` and + ``/proc/sys/fs/suid_dumpable`` + %s signal number + %t UNIX time of dump + %h hostname + %e executable filename (may be shortened) + %E executable path + %c maximum size of core file by resource limit RLIMIT_CORE + %<OTHER> both are dropped + ======== ========================================== * If the first character of the pattern is a '|', the kernel will treat the rest of the pattern as a command to run. The core dump will be written to the standard input of that program instead of to a file. -core_pipe_limit: -================ +core_pipe_limit +=============== -This sysctl is only applicable when core_pattern is configured to pipe -core files to a user space helper (when the first character of -core_pattern is a '|', see above). When collecting cores via a pipe -to an application, it is occasionally useful for the collecting -application to gather data about the crashing process from its -/proc/pid directory. In order to do this safely, the kernel must wait -for the collecting process to exit, so as not to remove the crashing -processes proc files prematurely. This in turn creates the -possibility that a misbehaving userspace collecting process can block -the reaping of a crashed process simply by never exiting. This sysctl -defends against that. It defines how many concurrent crashing -processes may be piped to user space applications in parallel. If -this value is exceeded, then those crashing processes above that value -are noted via the kernel log and their cores are skipped. 0 is a -special value, indicating that unlimited processes may be captured in -parallel, but that no waiting will take place (i.e. the collecting -process is not guaranteed access to /proc/<crashing pid>/). This -value defaults to 0. - - -core_uses_pid: -============== +This sysctl is only applicable when `core_pattern`_ is configured to +pipe core files to a user space helper (when the first character of +``core_pattern`` is a '|', see above). +When collecting cores via a pipe to an application, it is occasionally +useful for the collecting application to gather data about the +crashing process from its ``/proc/pid`` directory. +In order to do this safely, the kernel must wait for the collecting +process to exit, so as not to remove the crashing processes proc files +prematurely. +This in turn creates the possibility that a misbehaving userspace +collecting process can block the reaping of a crashed process simply +by never exiting. +This sysctl defends against that. +It defines how many concurrent crashing processes may be piped to user +space applications in parallel. +If this value is exceeded, then those crashing processes above that +value are noted via the kernel log and their cores are skipped. +0 is a special value, indicating that unlimited processes may be +captured in parallel, but that no waiting will take place (i.e. the +collecting process is not guaranteed access to ``/proc/<crashing +pid>/``). +This value defaults to 0. + + +core_uses_pid +============= The default coredump filename is "core". By setting -core_uses_pid to 1, the coredump filename becomes core.PID. -If core_pattern does not include "%p" (default does not) -and core_uses_pid is set, then .PID will be appended to +``core_uses_pid`` to 1, the coredump filename becomes core.PID. +If `core_pattern`_ does not include "%p" (default does not) +and ``core_uses_pid`` is set, then .PID will be appended to the filename. -ctrl-alt-del: -============= +ctrl-alt-del +============ When the value in this file is 0, ctrl-alt-del is trapped and -sent to the init(1) program to handle a graceful restart. +sent to the ``init(1)`` program to handle a graceful restart. When, however, the value is > 0, Linux's reaction to a Vulcan Nerve Pinch (tm) will be an immediate reboot, without even syncing its dirty buffers. @@ -269,21 +204,22 @@ Note: to decide what to do with it. -dmesg_restrict: -=============== +dmesg_restrict +============== This toggle indicates whether unprivileged users are prevented -from using dmesg(8) to view messages from the kernel's log buffer. -When dmesg_restrict is set to (0) there are no restrictions. When -dmesg_restrict is set set to (1), users must have CAP_SYSLOG to use -dmesg(8). +from using ``dmesg(8)`` to view messages from the kernel's log +buffer. +When ``dmesg_restrict`` is set to 0 there are no restrictions. +When ``dmesg_restrict`` is set set to 1, users must have +``CAP_SYSLOG`` to use ``dmesg(8)``. -The kernel config option CONFIG_SECURITY_DMESG_RESTRICT sets the -default value of dmesg_restrict. +The kernel config option ``CONFIG_SECURITY_DMESG_RESTRICT`` sets the +default value of ``dmesg_restrict``. -domainname & hostname: -====================== +domainname & hostname +===================== These files can be used to set the NIS/YP domainname and the hostname of your box in exactly the same way as the commands @@ -302,167 +238,206 @@ 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 hostname(1) man page. +see the ``hostname(1)`` man page. -hardlockup_all_cpu_backtrace: -============================= +hardlockup_all_cpu_backtrace +============================ This value controls the hard lockup detector behavior when a hard lockup condition is detected as to whether or not to gather further debug information. If enabled, arch-specific all-CPU stack dumping will be initiated. -0: do nothing. This is the default behavior. - -1: on detection capture more debug information. += ============================================ +0 Do nothing. This is the default behavior. +1 On detection capture more debug information. += ============================================ -hardlockup_panic: -================= +hardlockup_panic +================ This parameter can be used to control whether the kernel panics when a hard lockup is detected. - 0 - don't panic on hard lockup - 1 - panic on hard lockup += =========================== +0 Don't panic on hard lockup. +1 Panic on hard lockup. += =========================== -See Documentation/admin-guide/lockup-watchdogs.rst for more information. This can -also be set using the nmi_watchdog kernel parameter. +See :doc:`/admin-guide/lockup-watchdogs` for more information. +This can also be set using the nmi_watchdog kernel parameter. -hotplug: -======== +hotplug +======= Path for the hotplug policy agent. -Default value is "/sbin/hotplug". +Default value is "``/sbin/hotplug``". -hung_task_panic: -================ +hung_task_panic +=============== Controls the kernel's behavior when a hung task is detected. -This file shows up if CONFIG_DETECT_HUNG_TASK is enabled. - -0: continue operation. This is the default behavior. +This file shows up if ``CONFIG_DETECT_HUNG_TASK`` is enabled. -1: panic immediately. += ================================================= +0 Continue operation. This is the default behavior. +1 Panic immediately. += ================================================= -hung_task_check_count: -====================== +hung_task_check_count +===================== The upper bound on the number of tasks that are checked. -This file shows up if CONFIG_DETECT_HUNG_TASK is enabled. +This file shows up if ``CONFIG_DETECT_HUNG_TASK`` is enabled. -hung_task_timeout_secs: -======================= +hung_task_timeout_secs +====================== When a task in D state did not get scheduled for more than this value report a warning. -This file shows up if CONFIG_DETECT_HUNG_TASK is enabled. +This file shows up if ``CONFIG_DETECT_HUNG_TASK`` is enabled. -0: means infinite timeout - no checking done. +0 means infinite timeout, no checking is done. -Possible values to set are in range {0..LONG_MAX/HZ}. +Possible values to set are in range {0:``LONG_MAX``/``HZ``}. -hung_task_check_interval_secs: -============================== +hung_task_check_interval_secs +============================= Hung task check interval. If hung task checking is enabled -(see hung_task_timeout_secs), the check is done every -hung_task_check_interval_secs seconds. -This file shows up if CONFIG_DETECT_HUNG_TASK is enabled. +(see `hung_task_timeout_secs`_), the check is done every +``hung_task_check_interval_secs`` seconds. +This file shows up if ``CONFIG_DETECT_HUNG_TASK`` is enabled. -0 (default): means use hung_task_timeout_secs as checking interval. -Possible values to set are in range {0..LONG_MAX/HZ}. +0 (default) means use ``hung_task_timeout_secs`` as checking +interval. +Possible values to set are in range {0:``LONG_MAX``/``HZ``}. |