Documentation for /proc/sys/kernel/* kernel version 2.2.10
(c) 1998, 1999, Rik van Riel <riel@nl.linux.org>
+ (c) 2009, Shen Feng<shen@cn.fujitsu.com>
For general info and legal blurb, please look in README.
Currently, these files might (depending on your configuration)
show up in /proc/sys/kernel:
+- acpi_video_flags
- acct
+- 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
- hotplug
- java-appletviewer [ binfmt_java, obsolete ]
- java-interpreter [ binfmt_java, obsolete ]
+- kstack_depth_to_print [ X86 only ]
- l2cr [ PPC only ]
-- modprobe ==> Documentation/kmod.txt
+- modprobe ==> Documentation/debugging-modules.txt
+- modules_disabled
- msgmax
- msgmnb
- msgmni
+- nmi_watchdog
- osrelease
- ostype
- overflowgid
- panic
- pid_max
- powersave-nap [ PPC only ]
+- panic_on_unrecovered_nmi
- printk
+- randomize_va_space
- real-root-dev ==> Documentation/initrd.txt
- reboot-cmd [ SPARC only ]
- rtsig-max
- shmmax [ sysv ipc ]
- shmmni
- stop-a [ SPARC only ]
-- suid_dumpable
- sysrq ==> Documentation/sysrq.txt
- tainted
- threads-max
+- unknown_nmi_panic
- version
==============================================================
+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
==============================================================
+bootloader_type:
+
+x86 bootloader identification
+
+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
+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.txt for additional information.
+
+==============================================================
+
+bootloader_version:
+
+x86 bootloader version
+
+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.txt for additional information.
+
+==============================================================
+
+callhome:
+
+Controls the kernel's callhome behavior in case of a kernel panic.
+
+The s390 hardware allows an operating system to send a notification
+to a service organization (callhome) in case of an operating system panic.
+
+When the value in this file is 0 (which is the default behavior)
+nothing happens in case of a kernel panic. If this value is set to "1"
+the complete kernel oops message is send to the IBM customer service
+organization in case the mainframe the Linux operating system is running
+on has a service contract with IBM.
+
+==============================================================
+
core_pattern:
core_pattern is used to specify a core dumpfile pattern name.
-. max length 64 characters; default value is "core"
+. max length 128 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.
%h hostname
%e executable filename
%<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:
+
+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.
==============================================================
==============================================================
+kstack_depth_to_print: (X86 only)
+
+Controls the number of words to print when dumping the raw
+kernel stack.
+
+==============================================================
+
+modules_disabled:
+
+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.
+
+==============================================================
+
osrelease, ostype & version:
# cat osrelease
0: try to continue operation
-1: delay a few seconds (to give klogd time to record the oops output) and
- then panic. If the `panic' sysctl is also non-zero then the machine will
- be rebooted.
+1: panic immediately. If the `panic' sysctl is also non-zero then the
+ machine will be rebooted.
==============================================================
pid_max:
-PID allocation wrap value. When the kenrel's next PID value
+PID allocation wrap value. When the kernel's next PID value
reaches this value, it wraps back to a minimum PID value.
PIDs of value pid_max or larger are not allocated.
==============================================================
+printk_delay:
+
+Delay each printk message in printk_delay milliseconds
+
+Value from 0 - 10000 is allowed.
+
+==============================================================
+
+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
+that support this feature.
+
+0 - Turn the process address space randomization off. This is the
+ default for architectures that do not support this feature anyways,
+ and kernels that are booted with the "norandmaps" parameter.
+
+1 - Make the addresses of mmap base, stack and VDSO page randomized.
+ This, among other things, implies that shared libraries will be
+ loaded to random addresses. Also for PIE-linked binaries, the
+ location of code start is randomized. This is the default if the
+ CONFIG_COMPAT_BRK option is enabled.
+
+2 - Additionally enable heap randomization. This is the default if
+ CONFIG_COMPAT_BRK is disabled.
+
+ There are a few legacy applications out there (such as some ancient
+ versions of libc.so.5 from 1996) that assume that brk area starts
+ just after the end of the code+bss. These applications break when
+ start of the brk area is randomized. There are however no known
+ non-legacy applications that would be broken this way, so for most
+ systems it is safe to choose full randomization.
+
+ Systems with ancient and/or broken binaries should be configured
+ with CONFIG_COMPAT_BRK enabled, which excludes the heap from process
+ address space randomization.
+
+==============================================================
+
reboot-cmd: (Sparc only)
??? This seems to be a way to give an argument to the Sparc
==============================================================
-suid_dumpable:
-
-This value can be used to query and set the core dump mode for setuid
-or otherwise protected/tainted binaries. The modes are
+softlockup_thresh:
-0 - (default) - traditional behaviour. Any process which has changed
- privilege levels or is execute only will not be dumped
-1 - (debug) - all processes dump core when possible. The core dump is
- owned by the current user and no security is applied. This is
- intended for system debugging situations only. Ptrace is unchecked.
-2 - (suidsafe) - any binary which normally would not be dumped is dumped
- readable by root only. This allows the end user to remove
- such a dump but not access it directly. For security reasons
- core dumps in this mode will not overwrite one another or
- other files. This mode is appropriate when adminstrators are
- attempting to debug problems in a normal environment.
+This value can be used to lower the softlockup tolerance threshold. The
+default threshold is 60 seconds. If a cpu is locked up for 60 seconds,
+the kernel complains. Valid values are 1-60 seconds. Setting this
+tunable to zero will disable the softlockup detection altogether.
==============================================================
Non-zero if the kernel has been tainted. Numeric values, which
can be ORed together:
- 1 - A module with a non-GPL license has been loaded, this
- includes modules with no license.
- Set by modutils >= 2.4.9 and module-init-tools.
- 2 - A module was force loaded by insmod -f.
- Set by modutils >= 2.4.9 and module-init-tools.
- 4 - Unsafe SMP processors: SMP with CPUs not designed for SMP.
+ 1 - A module with a non-GPL license has been loaded, this
+ includes modules with no license.
+ Set by modutils >= 2.4.9 and module-init-tools.
+ 2 - A module was force loaded by insmod -f.
+ Set by modutils >= 2.4.9 and module-init-tools.
+ 4 - Unsafe SMP processors: SMP with CPUs not designed for SMP.
+ 8 - A module was forcibly unloaded from the system by rmmod -f.
+ 16 - A hardware machine check error occurred on the system.
+ 32 - A bad page was discovered on the system.
+ 64 - The user has asked that the system be marked "tainted". This
+ could be because they are running software that directly modifies
+ the hardware, or for other reasons.
+ 128 - The system has died.
+ 256 - The ACPI DSDT has been overridden with one supplied by the user
+ instead of using the one provided by the hardware.
+ 512 - A kernel warning has occurred.
+1024 - A module from drivers/staging was loaded.
+
+==============================================================
+
+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.
git://ftp.safe.ca / safe / jmp / linux-2.6 / blobdiff