linux/Documentation/sysctl
Linus Torvalds 73da9e1a9f Merge branch 'akpm' (patches from Andrew)
Merge updates from Andrew Morton:

 - misc fixes

 - ocfs2 updates

 - most of MM

* emailed patches from Andrew Morton <akpm@linux-foundation.org>: (118 commits)
  mm: remove PG_highmem description
  tools, vm: new option to specify kpageflags file
  mm/swap.c: make functions and their kernel-doc agree
  mm, memory_hotplug: fix memmap initialization
  mm: correct comments regarding do_fault_around()
  mm: numa: do not trap faults on shared data section pages.
  hugetlb, mbind: fall back to default policy if vma is NULL
  hugetlb, mempolicy: fix the mbind hugetlb migration
  mm, hugetlb: further simplify hugetlb allocation API
  mm, hugetlb: get rid of surplus page accounting tricks
  mm, hugetlb: do not rely on overcommit limit during migration
  mm, hugetlb: integrate giga hugetlb more naturally to the allocation path
  mm, hugetlb: unify core page allocation accounting and initialization
  mm/memcontrol.c: try harder to decrease [memory,memsw].limit_in_bytes
  mm/memcontrol.c: make local symbol static
  mm/hmm: fix uninitialized use of 'entry' in hmm_vma_walk_pmd()
  include/linux/mmzone.h: fix explanation of lower bits in the SPARSEMEM mem_map pointer
  mm/compaction.c: fix comment for try_to_compact_pages()
  mm/page_ext.c: make page_ext_init a noop when CONFIG_PAGE_EXTENSION but nothing uses it
  zsmalloc: use U suffix for negative literals being shifted
  ...
2018-01-31 18:46:22 -08:00
..
00-INDEX sysctl: remove obsolete comments 2011-01-13 08:03:18 -08:00
abi.txt
fs.txt docs: Update binfmt_misc links 2017-10-03 15:23:38 -06:00
kernel.txt Major additions: 2017-09-22 16:16:41 -10:00
net.txt net: Clarify dev_weight documentation for LRO and GRO_HW. 2017-12-20 13:04:01 -05:00
README docs: Update binfmt_misc links 2017-10-03 15:23:38 -06:00
sunrpc.txt
user.txt userns; Document per user per user namespace limits. 2016-09-22 12:52:03 -05:00
vm.txt mm, hugetlb: remove hugepages_treat_as_movable sysctl 2018-01-31 17:18:37 -08:00

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/admin-guide/binfmt-misc.rst>
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
user/		Per user per user namespace limits

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 :-)