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Diffstat (limited to 'Documentation/sysctl/kernel.txt')
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diff --git a/Documentation/sysctl/kernel.txt b/Documentation/sysctl/kernel.txt new file mode 100644 index 000000000000..35159176997b --- /dev/null +++ b/Documentation/sysctl/kernel.txt @@ -0,0 +1,314 @@ +Documentation for /proc/sys/kernel/* kernel version 2.2.10 + (c) 1998, 1999, Rik van Riel <riel@nl.linux.org> + +For general info and legal blurb, please look in README. + +============================================================== + +This file contains documentation for the sysctl files in +/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 +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 +- core_pattern +- core_uses_pid +- ctrl-alt-del +- dentry-state +- domainname +- hostname +- hotplug +- java-appletviewer [ binfmt_java, obsolete ] +- java-interpreter [ binfmt_java, obsolete ] +- l2cr [ PPC only ] +- modprobe ==> Documentation/kmod.txt +- msgmax +- msgmnb +- msgmni +- osrelease +- ostype +- overflowgid +- overflowuid +- panic +- pid_max +- powersave-nap [ PPC only ] +- printk +- real-root-dev ==> Documentation/initrd.txt +- reboot-cmd [ SPARC only ] +- rtsig-max +- rtsig-nr +- sem +- sg-big-buff [ generic SCSI device (sg) ] +- shmall +- shmmax [ sysv ipc ] +- shmmni +- stop-a [ SPARC only ] +- sysrq ==> Documentation/sysrq.txt +- tainted +- threads-max +- version + +============================================================== + +acct: + +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 +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. + +============================================================== + +core_pattern: + +core_pattern is used to specify a core dumpfile pattern name. +. max length 64 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: + 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 + %u uid + %g gid + %s signal number + %t UNIX time of dump + %h hostname + %e executable filename + %<OTHER> both are dropped + +============================================================== + +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 +the filename. + +============================================================== + +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. +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. + +Note: when a program (like dosemu) has the keyboard in 'raw' +mode, the ctrl-alt-del is intercepted by the program before it +ever reaches the kernel tty layer, and it's up to the program +to decide what to do with it. + +============================================================== + +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 +domainname and hostname, i.e.: +# echo "darkstar" > /proc/sys/kernel/hostname +# echo "mydomain" > /proc/sys/kernel/domainname +has the same effect as +# hostname "darkstar" +# domainname "mydomain" + +Note, however, that the classic darkstar.frop.org has the +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. + +============================================================== + +hotplug: + +Path for the hotplug policy agent. +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. + +============================================================== + +osrelease, ostype & version: + +# cat osrelease +2.1.88 +# cat ostype +Linux +# cat version +#5 Wed Feb 25 21:49:24 MET 1998 + +The files osrelease and ostype should be clear enough. Version +needs a little more clarification however. The '#5' means that +this is the fifth kernel built from this source base and the +date behind it indicates the time the kernel was built. +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. + +These sysctls allow you to change the value of the fixed UID and GID. +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. + +============================================================== + +panic_on_oops: + +Controls the kernel's behaviour when an oops or BUG is encountered. + +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. + +============================================================== + +pid_max: + +PID allocation wrap value. When the kenrel'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. + +============================================================== + +powersave-nap: (PPC only) + +If set, Linux-PPC will use the 'nap' mode of powersaving, +otherwise the 'doze' mode will be used. + +============================================================== + +printk: + +The four values in printk denote: console_loglevel, +default_message_loglevel, minimum_console_loglevel and +default_console_loglevel respectively. + +These values influence printk() behavior when printing or +logging error messages. See 'man 2 syslog' for more info on +the different loglevels. + +- console_loglevel: messages with a higher priority than + this will be printed to the console +- default_message_level: messages without an explicit priority + will be printed with this priority +- minimum_console_loglevel: minimum (highest) value to which + console_loglevel can be set +- default_console_loglevel: default value for console_loglevel + +============================================================== + +printk_ratelimit: + +Some warning messages are rate limited. printk_ratelimit specifies +the minimum length of time between these messages (in jiffies), by +default we allow one every 5 seconds. + +A value of 0 will disable rate limiting. + +============================================================== + +printk_ratelimit_burst: + +While long term we enforce one message per printk_ratelimit +seconds, we do allow a burst of messages to pass through. +printk_ratelimit_burst specifies the number of messages we can +send before ratelimiting kicks in. + +============================================================== + +reboot-cmd: (Sparc only) + +??? This seems to be a way to give an argument to the Sparc +ROM/Flash boot loader. Maybe to tell it what to do after +rebooting. ??? + +============================================================== + +rtsig-max & rtsig-nr: + +The file rtsig-max can be used to tune the maximum number +of POSIX realtime (queued) signals that can be outstanding +in the system. + +rtsig-nr shows the number of RT signals currently queued. + +============================================================== + +sg-big-buff: + +This file shows the size of the generic SCSI (sg) buffer. +You can't tune it just yet, but you could change it on +compile time by editing include/scsi/sg.h and changing +the value of SG_BIG_BUFF. + +There shouldn't be any reason to change this value. If +you can come up with one, you probably know what you +are doing anyway :) + +============================================================== + +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 +kernel. This value defaults to SHMMAX. + +============================================================== + +tainted: + +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. + |