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>hifive-unleashed-5.1
Borislav Petkov
Linus Torvalds
parent
9fd615f466
commit
807094c0b1
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@ -17,23 +17,21 @@ before actually making adjustments.
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Currently, these files might (depending on your configuration)
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show up in /proc/sys/kernel:
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- acpi_video_flags
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- acct
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- acpi_video_flags
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- auto_msgmni
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- bootloader_type [ X86 only ]
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- bootloader_version [ X86 only ]
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- callhome [ S390 only ]
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- auto_msgmni
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- core_pattern
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- core_pipe_limit
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- core_uses_pid
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- ctrl-alt-del
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- dentry-state
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- dmesg_restrict
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- domainname
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- hostname
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- hotplug
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- java-appletviewer [ binfmt_java, obsolete ]
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- java-interpreter [ binfmt_java, obsolete ]
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- kptr_restrict
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- kstack_depth_to_print [ X86 only ]
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- l2cr [ PPC only ]
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@ -48,10 +46,14 @@ show up in /proc/sys/kernel:
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- overflowgid
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- overflowuid
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- panic
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- panic_on_oops
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- panic_on_unrecovered_nmi
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- pid_max
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- powersave-nap [ PPC only ]
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- panic_on_unrecovered_nmi
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- printk
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- printk_delay
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- printk_ratelimit
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- printk_ratelimit_burst
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- randomize_va_space
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- real-root-dev ==> Documentation/initrd.txt
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- reboot-cmd [ SPARC only ]
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@ -62,6 +64,7 @@ show up in /proc/sys/kernel:
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- shmall
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- shmmax [ sysv ipc ]
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- shmmni
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- softlockup_thresh
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- stop-a [ SPARC only ]
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- sysrq ==> Documentation/sysrq.txt
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- tainted
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@ -71,15 +74,6 @@ show up in /proc/sys/kernel:
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==============================================================
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acpi_video_flags:
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flags
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See Doc*/kernel/power/video.txt, it allows mode of video boot to be
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set during run time.
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==============================================================
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acct:
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highwater lowwater frequency
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@ -95,6 +89,25 @@ That is, suspend accounting if there left <= 2% free; resume it
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if we got >=4%; consider information about amount of free space
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valid for 30 seconds.
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==============================================================
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acpi_video_flags:
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flags
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See Doc*/kernel/power/video.txt, it allows mode of video boot to be
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set during run time.
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==============================================================
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auto_msgmni:
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Enables/Disables automatic recomputing of msgmni upon memory add/remove
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or upon ipc namespace creation/removal (see the msgmni description
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above). Echoing "1" into this file enables msgmni automatic recomputing.
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Echoing "0" turns it off. auto_msgmni default value is 1.
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==============================================================
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bootloader_type:
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@ -172,22 +185,24 @@ core_pattern is used to specify a core dumpfile pattern name.
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core_pipe_limit:
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This sysctl is only applicable when core_pattern is configured to pipe core
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files to a user space helper (when the first character of core_pattern is a '|',
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see above). When collecting cores via a pipe to an application, it is
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occasionally useful for the collecting application to gather data about the
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crashing process from its /proc/pid directory. In order to do this safely, the
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kernel must wait for the collecting process to exit, so as not to remove the
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crashing processes proc files prematurely. This in turn creates the possibility
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that a misbehaving userspace collecting process can block the reaping of a
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crashed process simply by never exiting. This sysctl defends against that. It
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defines how many concurrent crashing processes may be piped to user space
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applications in parallel. If this value is exceeded, then those crashing
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processes above that value are noted via the kernel log and their cores are
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skipped. 0 is a special value, indicating that unlimited processes may be
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captured in parallel, but that no waiting will take place (i.e. the collecting
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process is not guaranteed access to /proc/<crashing pid>/). This value defaults
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to 0.
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This sysctl is only applicable when core_pattern is configured to pipe
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core files to a user space helper (when the first character of
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core_pattern is a '|', see above). When collecting cores via a pipe
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to an application, it is occasionally useful for the collecting
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application to gather data about the crashing process from its
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/proc/pid directory. In order to do this safely, the kernel must wait
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for the collecting process to exit, so as not to remove the crashing
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processes proc files prematurely. This in turn creates the
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possibility that a misbehaving userspace collecting process can block
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the reaping of a crashed process simply by never exiting. This sysctl
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defends against that. It defines how many concurrent crashing
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processes may be piped to user space applications in parallel. If
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this value is exceeded, then those crashing processes above that value
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are noted via the kernel log and their cores are skipped. 0 is a
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special value, indicating that unlimited processes may be captured in
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parallel, but that no waiting will take place (i.e. the collecting
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process is not guaranteed access to /proc/<crashing pid>/). This
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value defaults to 0.
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==============================================================
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@ -218,14 +233,14 @@ to decide what to do with it.
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dmesg_restrict:
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This toggle indicates whether unprivileged users are prevented from using
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dmesg(8) to view messages from the kernel's log buffer. When
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dmesg_restrict is set to (0) there are no restrictions. When
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This toggle indicates whether unprivileged users are prevented
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from using dmesg(8) to view messages from the kernel's log buffer.
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When dmesg_restrict is set to (0) there are no restrictions. When
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dmesg_restrict is set set to (1), users must have CAP_SYSLOG to use
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dmesg(8).
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The kernel config option CONFIG_SECURITY_DMESG_RESTRICT sets the default
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value of dmesg_restrict.
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The kernel config option CONFIG_SECURITY_DMESG_RESTRICT sets the
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default value of dmesg_restrict.
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==============================================================
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@ -256,13 +271,6 @@ Default value is "/sbin/hotplug".
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==============================================================
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l2cr: (PPC only)
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This flag controls the L2 cache of G3 processor boards. If
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0, the cache is disabled. Enabled if nonzero.
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==============================================================
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kptr_restrict:
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This toggle indicates whether restrictions are placed on
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@ -283,6 +291,13 @@ kernel stack.
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==============================================================
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l2cr: (PPC only)
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This flag controls the L2 cache of G3 processor boards. If
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0, the cache is disabled. Enabled if nonzero.
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==============================================================
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modules_disabled:
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A toggle value indicating if modules are allowed to be loaded
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@ -293,6 +308,21 @@ to false.
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==============================================================
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nmi_watchdog:
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Enables/Disables the NMI watchdog on x86 systems. When the value is
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non-zero the NMI watchdog is enabled and will continuously test all
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online cpus to determine whether or not they are still functioning
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properly. Currently, passing "nmi_watchdog=" parameter at boot time is
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required for this function to work.
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If LAPIC NMI watchdog method is in use (nmi_watchdog=2 kernel
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parameter), the NMI watchdog shares registers with oprofile. By
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disabling the NMI watchdog, oprofile may have more registers to
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utilize.
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==============================================================
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osrelease, ostype & version:
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# cat osrelease
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@ -312,10 +342,10 @@ The only way to tune these values is to rebuild the kernel :-)
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overflowgid & overflowuid:
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if your architecture did not always support 32-bit UIDs (i.e. arm, i386,
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m68k, sh, and sparc32), a fixed UID and GID will be returned to
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applications that use the old 16-bit UID/GID system calls, if the actual
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UID or GID would exceed 65535.
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if your architecture did not always support 32-bit UIDs (i.e. arm,
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i386, m68k, sh, and sparc32), a fixed UID and GID will be returned to
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applications that use the old 16-bit UID/GID system calls, if the
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actual UID or GID would exceed 65535.
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These sysctls allow you to change the value of the fixed UID and GID.
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The default is 65534.
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@ -324,9 +354,22 @@ The default is 65534.
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panic:
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The value in this file represents the number of seconds the
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kernel waits before rebooting on a panic. When you use the
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software watchdog, the recommended setting is 60.
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The value in this file represents the number of seconds the kernel
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waits before rebooting on a panic. When you use the software watchdog,
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the recommended setting is 60.
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==============================================================
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panic_on_unrecovered_nmi:
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The default Linux behaviour on an NMI of either memory or unknown is
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to continue operation. For many environments such as scientific
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computing it is preferable that the box is taken out and the error
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dealt with than an uncorrected parity/ECC error get propagated.
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A small number of systems do generate NMI's for bizarre random reasons
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such as power management so the default is off. That sysctl works like
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the existing panic controls already in that directory.
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==============================================================
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@ -376,6 +419,14 @@ the different loglevels.
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==============================================================
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printk_delay:
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Delay each printk message in printk_delay milliseconds
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Value from 0 - 10000 is allowed.
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==============================================================
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printk_ratelimit:
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Some warning messages are rate limited. printk_ratelimit specifies
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@ -395,15 +446,7 @@ send before ratelimiting kicks in.
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==============================================================
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printk_delay:
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Delay each printk message in printk_delay milliseconds
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Value from 0 - 10000 is allowed.
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==============================================================
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randomize-va-space:
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randomize_va_space:
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This option can be used to select the type of process address
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space randomization that is used in the system, for architectures
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@ -466,11 +509,11 @@ are doing anyway :)
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==============================================================
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shmmax:
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shmmax:
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This value can be used to query and set the run time limit
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on the maximum shared memory segment size that can be created.
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Shared memory segments up to 1Gb are now supported in the
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Shared memory segments up to 1Gb are now supported in the
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kernel. This value defaults to SHMMAX.
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==============================================================
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@ -484,7 +527,7 @@ tunable to zero will disable the softlockup detection altogether.
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==============================================================
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tainted:
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tainted:
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Non-zero if the kernel has been tainted. Numeric values, which
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can be ORed together:
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@ -509,49 +552,11 @@ can be ORed together:
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==============================================================
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auto_msgmni:
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Enables/Disables automatic recomputing of msgmni upon memory add/remove or
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upon ipc namespace creation/removal (see the msgmni description above).
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Echoing "1" into this file enables msgmni automatic recomputing.
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Echoing "0" turns it off.
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auto_msgmni default value is 1.
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==============================================================
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nmi_watchdog:
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Enables/Disables the NMI watchdog on x86 systems. When the value is non-zero
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the NMI watchdog is enabled and will continuously test all online cpus to
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determine whether or not they are still functioning properly. Currently,
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passing "nmi_watchdog=" parameter at boot time is required for this function
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to work.
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If LAPIC NMI watchdog method is in use (nmi_watchdog=2 kernel parameter), the
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NMI watchdog shares registers with oprofile. By disabling the NMI watchdog,
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oprofile may have more registers to utilize.
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==============================================================
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unknown_nmi_panic:
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The value in this file affects behavior of handling NMI. When the value is
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non-zero, unknown NMI is trapped and then panic occurs. At that time, kernel
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debugging information is displayed on console.
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NMI switch that most IA32 servers have fires unknown NMI up, for example.
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If a system hangs up, try pressing the NMI switch.
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==============================================================
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panic_on_unrecovered_nmi:
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The default Linux behaviour on an NMI of either memory or unknown is to continue
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operation. For many environments such as scientific computing it is preferable
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that the box is taken out and the error dealt with than an uncorrected
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parity/ECC error get propogated.
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A small number of systems do generate NMI's for bizarre random reasons such as
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power management so the default is off. That sysctl works like the existing
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panic controls already in that directory.
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The value in this file affects behavior of handling NMI. When the
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value is non-zero, unknown NMI is trapped and then panic occurs. At
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that time, kernel debugging information is displayed on console.
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NMI switch that most IA32 servers have fires unknown NMI up, for
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example. If a system hangs up, try pressing the NMI switch.
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