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authorLinus Torvalds <torvalds@ppc970.osdl.org>2005-04-16 15:20:36 -0700
committerLinus Torvalds <torvalds@ppc970.osdl.org>2005-04-16 15:20:36 -0700
commit1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 (patch)
tree0bba044c4ce775e45a88a51686b5d9f90697ea9d /Documentation/sysctl
downloadlinux-linaro-stable-1da177e4c3f41524e886b7f1b8a0c1fc7321cac2.tar.gz
Linux-2.6.12-rc2v2.6.12-rc2
Initial git repository build. I'm not bothering with the full history, even though we have it. We can create a separate "historical" git archive of that later if we want to, and in the meantime it's about 3.2GB when imported into git - space that would just make the early git days unnecessarily complicated, when we don't have a lot of good infrastructure for it. Let it rip!
Diffstat (limited to 'Documentation/sysctl')
-rw-r--r--Documentation/sysctl/README75
-rw-r--r--Documentation/sysctl/abi.txt54
-rw-r--r--Documentation/sysctl/fs.txt150
-rw-r--r--Documentation/sysctl/kernel.txt314
-rw-r--r--Documentation/sysctl/sunrpc.txt20
-rw-r--r--Documentation/sysctl/vm.txt104
6 files changed, 717 insertions, 0 deletions
diff --git a/Documentation/sysctl/README b/Documentation/sysctl/README
new file mode 100644
index 000000000000..8c3306e01d52
--- /dev/null
+++ b/Documentation/sysctl/README
@@ -0,0 +1,75 @@
+Documentation for /proc/sys/ kernel version 2.2.10
+ (c) 1998, 1999, Rik van Riel <riel@nl.linux.org>
+
+'Why', I hear you ask, 'would anyone even _want_ documentation
+for them sysctl files? If anybody really needs it, it's all in
+the source...'
+
+Well, this documentation is written because some people either
+don't know they need to tweak something, or because they don't
+have the time or knowledge to read the source code.
+
+Furthermore, the programmers who built sysctl have built it to
+be actually used, not just for the fun of programming it :-)
+
+==============================================================
+
+Legal blurb:
+
+As usual, there are two main things to consider:
+1. you get what you pay for
+2. it's free
+
+The consequences are that I won't guarantee the correctness of
+this document, and if you come to me complaining about how you
+screwed up your system because of wrong documentation, I won't
+feel sorry for you. I might even laugh at you...
+
+But of course, if you _do_ manage to screw up your system using
+only the sysctl options used in this file, I'd like to hear of
+it. Not only to have a great laugh, but also to make sure that
+you're the last RTFMing person to screw up.
+
+In short, e-mail your suggestions, corrections and / or horror
+stories to: <riel@nl.linux.org>
+
+Rik van Riel.
+
+==============================================================
+
+Introduction:
+
+Sysctl is a means of configuring certain aspects of the kernel
+at run-time, and the /proc/sys/ directory is there so that you
+don't even need special tools to do it!
+In fact, there are only four things needed to use these config
+facilities:
+- a running Linux system
+- root access
+- common sense (this is especially hard to come by these days)
+- knowledge of what all those values mean
+
+As a quick 'ls /proc/sys' will show, the directory consists of
+several (arch-dependent?) subdirs. Each subdir is mainly about
+one part of the kernel, so you can do configuration on a piece
+by piece basis, or just some 'thematic frobbing'.
+
+The subdirs are about:
+abi/ execution domains & personalities
+debug/ <empty>
+dev/ device specific information (eg dev/cdrom/info)
+fs/ specific filesystems
+ filehandle, inode, dentry and quota tuning
+ binfmt_misc <Documentation/binfmt_misc.txt>
+kernel/ global kernel info / tuning
+ miscellaneous stuff
+net/ networking stuff, for documentation look in:
+ <Documentation/networking/>
+proc/ <empty>
+sunrpc/ SUN Remote Procedure Call (NFS)
+vm/ memory management tuning
+ buffer and cache management
+
+These are the subdirs I have on my system. There might be more
+or other subdirs in another setup. If you see another dir, I'd
+really like to hear about it :-)
diff --git a/Documentation/sysctl/abi.txt b/Documentation/sysctl/abi.txt
new file mode 100644
index 000000000000..63f4ebcf652c
--- /dev/null
+++ b/Documentation/sysctl/abi.txt
@@ -0,0 +1,54 @@
+Documentation for /proc/sys/abi/* kernel version 2.6.0.test2
+ (c) 2003, Fabian Frederick <ffrederick@users.sourceforge.net>
+
+For general info : README.
+
+==============================================================
+
+This path is binary emulation relevant aka personality types aka abi.
+When a process is executed, it's linked to an exec_domain whose
+personality is defined using values available from /proc/sys/abi.
+You can find further details about abi in include/linux/personality.h.
+
+Here are the files featuring in 2.6 kernel :
+
+- defhandler_coff
+- defhandler_elf
+- defhandler_lcall7
+- defhandler_libcso
+- fake_utsname
+- trace
+
+===========================================================
+defhandler_coff:
+defined value :
+PER_SCOSVR3
+0x0003 | STICKY_TIMEOUTS | WHOLE_SECONDS | SHORT_INODE
+
+===========================================================
+defhandler_elf:
+defined value :
+PER_LINUX
+0
+
+===========================================================
+defhandler_lcall7:
+defined value :
+PER_SVR4
+0x0001 | STICKY_TIMEOUTS | MMAP_PAGE_ZERO,
+
+===========================================================
+defhandler_libsco:
+defined value:
+PER_SVR4
+0x0001 | STICKY_TIMEOUTS | MMAP_PAGE_ZERO,
+
+===========================================================
+fake_utsname:
+Unused
+
+===========================================================
+trace:
+Unused
+
+===========================================================
diff --git a/Documentation/sysctl/fs.txt b/Documentation/sysctl/fs.txt
new file mode 100644
index 000000000000..0b62c62142cf
--- /dev/null
+++ b/Documentation/sysctl/fs.txt
@@ -0,0 +1,150 @@
+Documentation for /proc/sys/fs/* 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/fs/ 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 are in /proc/sys/fs:
+- dentry-state
+- dquot-max
+- dquot-nr
+- file-max
+- file-nr
+- inode-max
+- inode-nr
+- inode-state
+- overflowuid
+- overflowgid
+- super-max
+- super-nr
+
+Documentation for the files in /proc/sys/fs/binfmt_misc is
+in Documentation/binfmt_misc.txt.
+
+==============================================================
+
+dentry-state:
+
+From linux/fs/dentry.c:
+--------------------------------------------------------------
+struct {
+ int nr_dentry;
+ int nr_unused;
+ int age_limit; /* age in seconds */
+ int want_pages; /* pages requested by system */
+ int dummy[2];
+} dentry_stat = {0, 0, 45, 0,};
+--------------------------------------------------------------
+
+Dentries are dynamically allocated and deallocated, and
+nr_dentry seems to be 0 all the time. Hence it's safe to
+assume that only nr_unused, age_limit and want_pages are
+used. Nr_unused seems to be exactly what its name says.
+Age_limit is the age in seconds after which dcache entries
+can be reclaimed when memory is short and want_pages is
+nonzero when shrink_dcache_pages() has been called and the
+dcache isn't pruned yet.
+
+==============================================================
+
+dquot-max & dquot-nr:
+
+The file dquot-max shows the maximum number of cached disk
+quota entries.
+
+The file dquot-nr shows the number of allocated disk quota
+entries and the number of free disk quota entries.
+
+If the number of free cached disk quotas is very low and
+you have some awesome number of simultaneous system users,
+you might want to raise the limit.
+
+==============================================================
+
+file-max & file-nr:
+
+The kernel allocates file handles dynamically, but as yet it
+doesn't free them again.
+
+The value in file-max denotes the maximum number of file-
+handles that the Linux kernel will allocate. When you get lots
+of error messages about running out of file handles, you might
+want to increase this limit.
+
+The three values in file-nr denote the number of allocated
+file handles, the number of unused file handles and the maximum
+number of file handles. When the allocated file handles come
+close to the maximum, but the number of unused file handles is
+significantly greater than 0, you've encountered a peak in your
+usage of file handles and you don't need to increase the maximum.
+
+==============================================================
+
+inode-max, inode-nr & inode-state:
+
+As with file handles, the kernel allocates the inode structures
+dynamically, but can't free them yet.
+
+The value in inode-max denotes the maximum number of inode
+handlers. This value should be 3-4 times larger than the value
+in file-max, since stdin, stdout and network sockets also
+need an inode struct to handle them. When you regularly run
+out of inodes, you need to increase this value.
+
+The file inode-nr contains the first two items from
+inode-state, so we'll skip to that file...
+
+Inode-state contains three actual numbers and four dummies.
+The actual numbers are, in order of appearance, nr_inodes,
+nr_free_inodes and preshrink.
+
+Nr_inodes stands for the number of inodes the system has
+allocated, this can be slightly more than inode-max because
+Linux allocates them one pageful at a time.
+
+Nr_free_inodes represents the number of free inodes (?) and
+preshrink is nonzero when the nr_inodes > inode-max and the
+system needs to prune the inode list instead of allocating
+more.
+
+==============================================================
+
+overflowgid & overflowuid:
+
+Some filesystems only support 16-bit UIDs and GIDs, although in Linux
+UIDs and GIDs are 32 bits. When one of these filesystems is mounted
+with writes enabled, any UID or GID that would exceed 65535 is translated
+to a fixed value before being written to disk.
+
+These sysctls allow you to change the value of the fixed UID and GID.
+The default is 65534.
+
+==============================================================
+
+super-max & super-nr:
+
+These numbers control the maximum number of superblocks, and
+thus the maximum number of mounted filesystems the kernel
+can have. You only need to increase super-max if you need to
+mount more filesystems than the current value in super-max
+allows you to.
+
+==============================================================
+
+aio-nr & aio-max-nr:
+
+aio-nr shows the current system-wide number of asynchronous io
+requests. aio-max-nr allows you to change the maximum value
+aio-nr can grow to.
+
+==============================================================
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.
+
diff --git a/Documentation/sysctl/sunrpc.txt b/Documentation/sysctl/sunrpc.txt
new file mode 100644
index 000000000000..ae1ecac6f85a
--- /dev/null
+++ b/Documentation/sysctl/sunrpc.txt
@@ -0,0 +1,20 @@
+Documentation for /proc/sys/sunrpc/* 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 the documentation for the sysctl files in
+/proc/sys/sunrpc and is valid for Linux kernel version 2.2.
+
+The files in this directory can be used to (re)set the debug
+flags of the SUN Remote Procedure Call (RPC) subsystem in
+the Linux kernel. This stuff is used for NFS, KNFSD and
+maybe a few other things as well.
+
+The files in there are used to control the debugging flags:
+rpc_debug, nfs_debug, nfsd_debug and nlm_debug.
+
+These flags are for kernel hackers only. You should read the
+source code in net/sunrpc/ for more information.
diff --git a/Documentation/sysctl/vm.txt b/Documentation/sysctl/vm.txt
new file mode 100644
index 000000000000..2f1aae32a5d9
--- /dev/null
+++ b/Documentation/sysctl/vm.txt
@@ -0,0 +1,104 @@
+Documentation for /proc/sys/vm/* 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 the documentation for the sysctl files in
+/proc/sys/vm and is valid for Linux kernel version 2.2.
+
+The files in this directory can be used to tune the operation
+of the virtual memory (VM) subsystem of the Linux kernel and
+the writeout of dirty data to disk.
+
+Default values and initialization routines for most of these
+files can be found in mm/swap.c.
+
+Currently, these files are in /proc/sys/vm:
+- overcommit_memory
+- page-cluster
+- dirty_ratio
+- dirty_background_ratio
+- dirty_expire_centisecs
+- dirty_writeback_centisecs
+- max_map_count
+- min_free_kbytes
+- laptop_mode
+- block_dump
+
+==============================================================
+
+dirty_ratio, dirty_background_ratio, dirty_expire_centisecs,
+dirty_writeback_centisecs, vfs_cache_pressure, laptop_mode,
+block_dump, swap_token_timeout:
+
+See Documentation/filesystems/proc.txt
+
+==============================================================
+
+overcommit_memory:
+
+This value contains a flag that enables memory overcommitment.
+
+When this flag is 0, the kernel attempts to estimate the amount
+of free memory left when userspace requests more memory.
+
+When this flag is 1, the kernel pretends there is always enough
+memory until it actually runs out.
+
+When this flag is 2, the kernel uses a "never overcommit"
+policy that attempts to prevent any overcommit of memory.
+
+This feature can be very useful because there are a lot of
+programs that malloc() huge amounts of memory "just-in-case"
+and don't use much of it.
+
+The default value is 0.
+
+See Documentation/vm/overcommit-accounting and
+security/commoncap.c::cap_vm_enough_memory() for more information.
+
+==============================================================
+
+overcommit_ratio:
+
+When overcommit_memory is set to 2, the committed address
+space is not permitted to exceed swap plus this percentage
+of physical RAM. See above.
+
+==============================================================
+
+page-cluster:
+
+The Linux VM subsystem avoids excessive disk seeks by reading
+multiple pages on a page fault. The number of pages it reads
+is dependent on the amount of memory in your machine.
+
+The number of pages the kernel reads in at once is equal to
+2 ^ page-cluster. Values above 2 ^ 5 don't make much sense
+for swap because we only cluster swap data in 32-page groups.
+
+==============================================================
+
+max_map_count:
+
+This file contains the maximum number of memory map areas a process
+may have. Memory map areas are used as a side-effect of calling
+malloc, directly by mmap and mprotect, and also when loading shared
+libraries.
+
+While most applications need less than a thousand maps, certain
+programs, particularly malloc debuggers, may consume lots of them,
+e.g., up to one or two maps per allocation.
+
+The default value is 65536.
+
+==============================================================
+
+min_free_kbytes:
+
+This is used to force the Linux VM to keep a minimum number
+of kilobytes free. The VM uses this number to compute a pages_min
+value for each lowmem zone in the system. Each lowmem zone gets
+a number of reserved free pages based proportionally on its size.