Re: [PATCH] Documentation: Refresh sysctl/kernel.txt

From: Randy Dunlap
Date: Mon Jul 18 2011 - 13:49:24 EST


On Sat, 16 Jul 2011 10:23:21 +0200 Borislav Petkov wrote:

> 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@xxxxxxxxx>

Applied, thanks.

> ---
> Documentation/sysctl/kernel.txt | 215 ++++++++++++++++++++-------------------
> 1 files changed, 110 insertions(+), 105 deletions(-)
>
> diff --git a/Documentation/sysctl/kernel.txt b/Documentation/sysctl/kernel.txt
> index 5e7cb39..1c7fb0a 100644
> --- a/Documentation/sysctl/kernel.txt
> +++ b/Documentation/sysctl/kernel.txt
> @@ -17,23 +17,21 @@ before actually making adjustments.
>
> Currently, these files might (depending on your configuration)
> show up in /proc/sys/kernel:
> -- acpi_video_flags
> +
> - acct
> +- acpi_video_flags
> +- auto_msgmni
> - bootloader_type [ X86 only ]
> - bootloader_version [ X86 only ]
> - callhome [ S390 only ]
> -- auto_msgmni
> - core_pattern
> - core_pipe_limit
> - core_uses_pid
> - ctrl-alt-del
> -- dentry-state
> - dmesg_restrict
> - domainname
> - hostname
> - hotplug
> -- java-appletviewer [ binfmt_java, obsolete ]
> -- java-interpreter [ binfmt_java, obsolete ]
> - kptr_restrict
> - kstack_depth_to_print [ X86 only ]
> - l2cr [ PPC only ]
> @@ -48,10 +46,14 @@ show up in /proc/sys/kernel:
> - overflowgid
> - overflowuid
> - panic
> +- panic_on_oops
> +- panic_on_unrecovered_nmi
> - pid_max
> - powersave-nap [ PPC only ]
> -- panic_on_unrecovered_nmi
> - printk
> +- printk_delay
> +- printk_ratelimit
> +- printk_ratelimit_burst
> - randomize_va_space
> - real-root-dev ==> Documentation/initrd.txt
> - reboot-cmd [ SPARC only ]
> @@ -62,6 +64,7 @@ show up in /proc/sys/kernel:
> - shmall
> - shmmax [ sysv ipc ]
> - shmmni
> +- softlockup_thresh
> - stop-a [ SPARC only ]
> - sysrq ==> Documentation/sysrq.txt
> - tainted
> @@ -71,15 +74,6 @@ show up in /proc/sys/kernel:
>
> ==============================================================
>
> -acpi_video_flags:
> -
> -flags
> -
> -See Doc*/kernel/power/video.txt, it allows mode of video boot to be
> -set during run time.
> -
> -==============================================================
> -
> acct:
>
> highwater lowwater frequency
> @@ -97,6 +91,25 @@ valid for 30 seconds.
>
> ==============================================================
>
> +acpi_video_flags:
> +
> +flags
> +
> +See Doc*/kernel/power/video.txt, it allows mode of video boot to be
> +set during run time.
> +
> +==============================================================
> +
> +auto_msgmni:
> +
> +Enables/Disables automatic recomputing of msgmni upon memory add/remove
> +or upon ipc namespace creation/removal (see the msgmni description
> +above). Echoing "1" into this file enables msgmni automatic recomputing.
> +Echoing "0" turns it off. auto_msgmni default value is 1.
> +
> +
> +==============================================================
> +
> bootloader_type:
>
> x86 bootloader identification
> @@ -172,22 +185,24 @@ core_pattern is used to specify a core dumpfile pattern name.
>
> 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.
> +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.
>
> ==============================================================
>
> @@ -218,14 +233,14 @@ to decide what to do with it.
>
> 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
> +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).
>
> -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.
>
> ==============================================================
>
> @@ -256,13 +271,6 @@ Default value is "/sbin/hotplug".
>
> ==============================================================
>
> -l2cr: (PPC only)
> -
> -This flag controls the L2 cache of G3 processor boards. If
> -0, the cache is disabled. Enabled if nonzero.
> -
> -==============================================================
> -
> kptr_restrict:
>
> This toggle indicates whether restrictions are placed on
> @@ -283,6 +291,13 @@ kernel stack.
>
> ==============================================================
>
> +l2cr: (PPC only)
> +
> +This flag controls the L2 cache of G3 processor boards. If
> +0, the cache is disabled. Enabled if nonzero.
> +
> +==============================================================
> +
> modules_disabled:
>
> A toggle value indicating if modules are allowed to be loaded
> @@ -293,6 +308,21 @@ to false.
>
> ==============================================================
>
> +nmi_watchdog:
> +
> +Enables/Disables the NMI watchdog on x86 systems. When the value is
> +non-zero the NMI watchdog is enabled and will continuously test all
> +online cpus to determine whether or not they are still functioning
> +properly. Currently, passing "nmi_watchdog=" parameter at boot time is
> +required for this function to work.
> +
> +If LAPIC NMI watchdog method is in use (nmi_watchdog=2 kernel
> +parameter), the NMI watchdog shares registers with oprofile. By
> +disabling the NMI watchdog, oprofile may have more registers to
> +utilize.
> +
> +==============================================================
> +
> osrelease, ostype & version:
>
> # cat osrelease
> @@ -312,10 +342,10 @@ The only way to tune these values is to rebuild the kernel :-)
>
> overflowgid & overflowuid:
>
> -if your architecture did not always support 32-bit UIDs (i.e. arm, i386,
> -m68k, sh, and sparc32), a fixed UID and GID will be returned to
> -applications that use the old 16-bit UID/GID system calls, if the actual
> -UID or GID would exceed 65535.
> +if your architecture did not always support 32-bit UIDs (i.e. arm,
> +i386, m68k, sh, and sparc32), a fixed UID and GID will be returned to
> +applications that use the old 16-bit UID/GID system calls, if the
> +actual UID or GID would exceed 65535.
>
> These sysctls allow you to change the value of the fixed UID and GID.
> The default is 65534.
> @@ -324,9 +354,22 @@ The default is 65534.
>
> panic:
>
> -The value in this file represents the number of seconds the
> -kernel waits before rebooting on a panic. When you use the
> -software watchdog, the recommended setting is 60.
> +The value in this file represents the number of seconds the kernel
> +waits before rebooting on a panic. When you use the software watchdog,
> +the recommended setting is 60.
> +
> +==============================================================
> +
> +panic_on_unrecovered_nmi:
> +
> +The default Linux behaviour on an NMI of either memory or unknown is
> +to continue operation. For many environments such as scientific
> +computing it is preferable that the box is taken out and the error
> +dealt with than an uncorrected parity/ECC error get propagated.
> +
> +A small number of systems do generate NMI's for bizarre random reasons
> +such as power management so the default is off. That sysctl works like
> +the existing panic controls already in that directory.
>
> ==============================================================
>
> @@ -376,6 +419,14 @@ the different loglevels.
>
> ==============================================================
>
> +printk_delay:
> +
> +Delay each printk message in printk_delay milliseconds
> +
> +Value from 0 - 10000 is allowed.
> +
> +==============================================================
> +
> printk_ratelimit:
>
> Some warning messages are rate limited. printk_ratelimit specifies
> @@ -395,15 +446,7 @@ send before ratelimiting kicks in.
>
> ==============================================================
>
> -printk_delay:
> -
> -Delay each printk message in printk_delay milliseconds
> -
> -Value from 0 - 10000 is allowed.
> -
> -==============================================================
> -
> -randomize-va-space:
> +randomize_va_space:
>
> This option can be used to select the type of process address
> space randomization that is used in the system, for architectures
> @@ -466,11 +509,11 @@ are doing anyway :)
>
> ==============================================================
>
> -shmmax:
> +shmmax:
>
> This value can be used to query and set the run time limit
> on the maximum shared memory segment size that can be created.
> -Shared memory segments up to 1Gb are now supported in the
> +Shared memory segments up to 1Gb are now supported in the
> kernel. This value defaults to SHMMAX.
>
> ==============================================================
> @@ -484,7 +527,7 @@ tunable to zero will disable the softlockup detection altogether.
>
> ==============================================================
>
> -tainted:
> +tainted:
>
> Non-zero if the kernel has been tainted. Numeric values, which
> can be ORed together:
> @@ -509,49 +552,11 @@ can be ORed together:
>
> ==============================================================
>
> -auto_msgmni:
> -
> -Enables/Disables automatic recomputing of msgmni upon memory add/remove or
> -upon ipc namespace creation/removal (see the msgmni description above).
> -Echoing "1" into this file enables msgmni automatic recomputing.
> -Echoing "0" turns it off.
> -auto_msgmni default value is 1.
> -
> -==============================================================
> -
> -nmi_watchdog:
> -
> -Enables/Disables the NMI watchdog on x86 systems. When the value is non-zero
> -the NMI watchdog is enabled and will continuously test all online cpus to
> -determine whether or not they are still functioning properly. Currently,
> -passing "nmi_watchdog=" parameter at boot time is required for this function
> -to work.
> -
> -If LAPIC NMI watchdog method is in use (nmi_watchdog=2 kernel parameter), the
> -NMI watchdog shares registers with oprofile. By disabling the NMI watchdog,
> -oprofile may have more registers to utilize.
> -
> -==============================================================
> -
> unknown_nmi_panic:
>
> -The value in this file affects behavior of handling NMI. When the value is
> -non-zero, unknown NMI is trapped and then panic occurs. At that time, kernel
> -debugging information is displayed on console.
> -
> -NMI switch that most IA32 servers have fires unknown NMI up, for example.
> -If a system hangs up, try pressing the NMI switch.
> -
> -==============================================================
> -
> -panic_on_unrecovered_nmi:
> -
> -The default Linux behaviour on an NMI of either memory or unknown is to continue
> -operation. For many environments such as scientific computing it is preferable
> -that the box is taken out and the error dealt with than an uncorrected
> -parity/ECC error get propogated.
> -
> -A small number of systems do generate NMI's for bizarre random reasons such as
> -power management so the default is off. That sysctl works like the existing
> -panic controls already in that directory.
> +The value in this file affects behavior of handling NMI. When the
> +value is non-zero, unknown NMI is trapped and then panic occurs. At
> +that time, kernel debugging information is displayed on console.
>
> +NMI switch that most IA32 servers have fires unknown NMI up, for
> +example. If a system hangs up, try pressing the NMI switch.
> --


---
~Randy
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