diff options
Diffstat (limited to 'Documentation/sysctl/kernel.txt')
| -rw-r--r-- | Documentation/sysctl/kernel.txt | 237 |
1 files changed, 132 insertions, 105 deletions
diff --git a/Documentation/sysctl/kernel.txt b/Documentation/sysctl/kernel.txt index 5e7cb39ad195..704e474a93df 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 ] @@ -59,9 +61,11 @@ show up in /proc/sys/kernel: - rtsig-nr - sem - sg-big-buff [ generic SCSI device (sg) ] +- shm_rmid_forced - shmall - shmmax [ sysv ipc ] - shmmni +- softlockup_thresh - stop-a [ SPARC only ] - sysrq ==> Documentation/sysrq.txt - tainted @@ -71,15 +75,6 @@ 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 +92,25 @@ 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 +186,24 @@ 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 +234,14 @@ 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 +272,6 @@ 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 +292,13 @@ 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 +309,21 @@ 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 +343,10 @@ 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 +355,22 @@ 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 +420,14 @@ 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 +447,7 @@ 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 @@ -466,15 +510,36 @@ 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. ============================================================== +shm_rmid_forced: + +Linux lets you set resource limits, including how much memory one +process can consume, via setrlimit(2). Unfortunately, shared memory +segments are allowed to exist without association with any process, and +thus might not be counted against any resource limits. If enabled, +shared memory segments are automatically destroyed when their attach +count becomes zero after a detach or a process termination. It will +also destroy segments that were created, but never attached to, on exit +from the process. The only use left for IPC_RMID is to immediately +destroy an unattached segment. Of course, this breaks the way things are +defined, so some applications might stop working. Note that this +feature will do you no good unless you also configure your resource +limits (in particular, RLIMIT_AS and RLIMIT_NPROC). Most systems don't +need this. + +Note that if you change this from 0 to 1, already created segments +without users and with a dead originative process will be destroyed. + +============================================================== + softlockup_thresh: This value can be used to lower the softlockup tolerance threshold. The @@ -484,7 +549,7 @@ 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 +574,11 @@ 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. |