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Commit 760df93e authored by Shen Feng's avatar Shen Feng Committed by Linus Torvalds
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documentation: update Documentation/filesystem/proc.txt and Documentation/sysctls 

Now /proc/sys is described in many places and much information is
redundant.  This patch updates the proc.txt and move the /proc/sys
desciption out to the files in Documentation/sysctls.

Details are:

merge
-  2.1  /proc/sys/fs - File system data
-  2.11 /proc/sys/fs/mqueue - POSIX message queues filesystem
-  2.17 /proc/sys/fs/epoll - Configuration options for the epoll interface
with Documentation/sysctls/fs.txt.

remove
-  2.2  /proc/sys/fs/binfmt_misc - Miscellaneous binary formats
since it's not better then the Documentation/binfmt_misc.txt.

merge
-  2.3  /proc/sys/kernel - general kernel parameters
with Documentation/sysctls/kernel.txt

remove
-  2.5  /proc/sys/dev - Device specific parameters
since it's obsolete the sysfs is used now.

remove
-  2.6  /proc/sys/sunrpc - Remote procedure calls
since it's not better then the Documentation/sysctls/sunrpc.txt

move
-  2.7  /proc/sys/net - Networking stuff
-  2.9  Appletalk
-  2.10 IPX
to newly created Documentation/sysctls/net.txt.

remove
-  2.8  /proc/sys/net/ipv4 - IPV4 settings
since it's not better then the Documentation/networking/ip-sysctl.txt.

add
- Chapter 3 Per-Process Parameters
to descibe /proc/<pid>/xxx parameters.
Signed-off-by: default avatarShen Feng <shen@cn.fujitsu.com>
Cc: Randy Dunlap <randy.dunlap@oracle.com>
Cc: "David S. Miller" <davem@davemloft.net>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 70eed8d0
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Showing with 329 additions and 1071 deletions
Documentation/filesystems/proc.txt
View file @ 760df93e
......@@ -5,6 +5,7 @@
Bodo Bauer <bb@ricochet.net>
2.4.x update Jorge Nerin <comandante@zaralinux.com> November 14 2000
move /proc/sys Shen Feng <shen@cn.fujitsu.com> April 1 2009
------------------------------------------------------------------------------
Version 1.3 Kernel version 2.2.12
Kernel version 2.4.0-test11-pre4
......@@ -26,25 +27,17 @@ Table of Contents
1.6 Parallel port info in /proc/parport
1.7 TTY info in /proc/tty
1.8 Miscellaneous kernel statistics in /proc/stat
1.9 Ext4 file system parameters
2 Modifying System Parameters
2.1 /proc/sys/fs - File system data
2.2 /proc/sys/fs/binfmt_misc - Miscellaneous binary formats
2.3 /proc/sys/kernel - general kernel parameters
2.4 /proc/sys/vm - The virtual memory subsystem
2.5 /proc/sys/dev - Device specific parameters
2.6 /proc/sys/sunrpc - Remote procedure calls
2.7 /proc/sys/net - Networking stuff
2.8 /proc/sys/net/ipv4 - IPV4 settings
2.9 Appletalk
2.10 IPX
2.11 /proc/sys/fs/mqueue - POSIX message queues filesystem
2.12 /proc/<pid>/oom_adj - Adjust the oom-killer score
2.13 /proc/<pid>/oom_score - Display current oom-killer score
2.14 /proc/<pid>/io - Display the IO accounting fields
2.15 /proc/<pid>/coredump_filter - Core dump filtering settings
2.16 /proc/<pid>/mountinfo - Information about mounts
2.17 /proc/sys/fs/epoll - Configuration options for the epoll interface
3 Per-Process Parameters
3.1 /proc/<pid>/oom_adj - Adjust the oom-killer score
3.2 /proc/<pid>/oom_score - Display current oom-killer score
3.3 /proc/<pid>/io - Display the IO accounting fields
3.4 /proc/<pid>/coredump_filter - Core dump filtering settings
3.5 /proc/<pid>/mountinfo - Information about mounts
------------------------------------------------------------------------------
Preface
......@@ -990,1021 +983,24 @@ review the kernel documentation in the directory /usr/src/linux/Documentation.
This chapter is heavily based on the documentation included in the pre 2.2
kernels, and became part of it in version 2.2.1 of the Linux kernel.
2.1 /proc/sys/fs - File system data
-----------------------------------
This subdirectory contains specific file system, file handle, inode, dentry
and quota information.
Currently, these files are in /proc/sys/fs:
dentry-state
------------
Status of the directory cache. Since directory entries are dynamically
allocated and deallocated, this file indicates the current status. It holds
six values, in which the last two are not used and are always zero. The others
are listed in table 2-1.
Table 2-1: Status files of the directory cache
..............................................................................
File Content
nr_dentry Almost always zero
nr_unused Number of unused cache entries
age_limit
in seconds after the entry may be reclaimed, when memory is short
want_pages internally
..............................................................................
dquot-nr and dquot-max
----------------------
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 available cached disk quotas is very low and you have a large
number of simultaneous system users, you might want to raise the limit.
file-nr and file-max
--------------------
The kernel allocates file handles dynamically, but doesn't free them again at
this time.
The value in file-max denotes the maximum number of file handles that the
Linux kernel will allocate. When you get a lot of error messages about running
out of file handles, you might want to raise this limit. The default value is
10% of RAM in kilobytes. To change it, just write the new number into the
file:
# cat /proc/sys/fs/file-max
4096
# echo 8192 > /proc/sys/fs/file-max
# cat /proc/sys/fs/file-max
8192
This method of revision is useful for all customizable parameters of the
kernel - simply echo the new value to the corresponding file.
Historically, the three values in file-nr denoted the number of allocated file
handles, the number of allocated but unused file handles, and the maximum
number of file handles. Linux 2.6 always reports 0 as the number of free file
handles -- this is not an error, it just means that the number of allocated
file handles exactly matches the number of used file handles.
Attempts to allocate more file descriptors than file-max are reported with
printk, look for "VFS: file-max limit <number> reached".
inode-state and inode-nr
------------------------
The file inode-nr contains the first two items from inode-state, so we'll skip
to that file...
inode-state contains two actual numbers and five dummy values. The numbers
are nr_inodes and nr_free_inodes (in order of appearance).
nr_inodes
~~~~~~~~~
Denotes the number of inodes the system has allocated. This number will
grow and shrink dynamically.
nr_open
-------
Denotes the maximum number of file-handles a process can
allocate. Default value is 1024*1024 (1048576) which should be
enough for most machines. Actual limit depends on RLIMIT_NOFILE
resource limit.
nr_free_inodes
--------------
Represents the number of free inodes. Ie. The number of inuse inodes is
(nr_inodes - nr_free_inodes).
aio-nr and aio-max-nr
---------------------
aio-nr is the running total of the number of events specified on the
io_setup system call for all currently active aio contexts. If aio-nr
reaches aio-max-nr then io_setup will fail with EAGAIN. Note that
raising aio-max-nr does not result in the pre-allocation or re-sizing
of any kernel data structures.
2.2 /proc/sys/fs/binfmt_misc - Miscellaneous binary formats
-----------------------------------------------------------
Besides these files, there is the subdirectory /proc/sys/fs/binfmt_misc. This
handles the kernel support for miscellaneous binary formats.
Binfmt_misc provides the ability to register additional binary formats to the
Kernel without compiling an additional module/kernel. Therefore, binfmt_misc
needs to know magic numbers at the beginning or the filename extension of the
binary.
It works by maintaining a linked list of structs that contain a description of
a binary format, including a magic with size (or the filename extension),
offset and mask, and the interpreter name. On request it invokes the given
interpreter with the original program as argument, as binfmt_java and
binfmt_em86 and binfmt_mz do. Since binfmt_misc does not define any default
binary-formats, you have to register an additional binary-format.
There are two general files in binfmt_misc and one file per registered format.
The two general files are register and status.
Registering a new binary format
-------------------------------
To register a new binary format you have to issue the command
echo :name:type:offset:magic:mask:interpreter: > /proc/sys/fs/binfmt_misc/register
with appropriate name (the name for the /proc-dir entry), offset (defaults to
0, if omitted), magic, mask (which can be omitted, defaults to all 0xff) and
last but not least, the interpreter that is to be invoked (for example and
testing /bin/echo). Type can be M for usual magic matching or E for filename
extension matching (give extension in place of magic).
Check or reset the status of the binary format handler
------------------------------------------------------
If you do a cat on the file /proc/sys/fs/binfmt_misc/status, you will get the
current status (enabled/disabled) of binfmt_misc. Change the status by echoing
0 (disables) or 1 (enables) or -1 (caution: this clears all previously
registered binary formats) to status. For example echo 0 > status to disable
binfmt_misc (temporarily).
Status of a single handler
--------------------------
Each registered handler has an entry in /proc/sys/fs/binfmt_misc. These files
perform the same function as status, but their scope is limited to the actual
binary format. By cating this file, you also receive all related information
about the interpreter/magic of the binfmt.
Example usage of binfmt_misc (emulate binfmt_java)
--------------------------------------------------
cd /proc/sys/fs/binfmt_misc
echo ':Java:M::\xca\xfe\xba\xbe::/usr/local/java/bin/javawrapper:' > register
echo ':HTML:E::html::/usr/local/java/bin/appletviewer:' > register
echo ':Applet:M::<!--applet::/usr/local/java/bin/appletviewer:' > register
echo ':DEXE:M::\x0eDEX::/usr/bin/dosexec:' > register
These four lines add support for Java executables and Java applets (like
binfmt_java, additionally recognizing the .html extension with no need to put
<!--applet> to every applet file). You have to install the JDK and the
shell-script /usr/local/java/bin/javawrapper too. It works around the
brokenness of the Java filename handling. To add a Java binary, just create a
link to the class-file somewhere in the path.
2.3 /proc/sys/kernel - general kernel parameters
------------------------------------------------
This directory reflects general kernel behaviors. As I've said before, the
contents depend on your configuration. Here you'll find the most important
files, along with descriptions of what they mean and how to use them.
acct
----
The file contains three values; highwater, lowwater, and frequency.
It exists only when BSD-style process accounting is enabled. These values
control its behavior. If the free space on the file system where the log lives
goes below lowwater percentage, accounting suspends. If it goes above
highwater percentage, accounting resumes. Frequency determines how often you
check the amount of free space (value is in seconds). Default settings are: 4,
2, and 30. That is, suspend accounting if there is less than 2 percent free;
resume it if we have a value of 3 or more percent; consider information about
the amount of free space valid for 30 seconds
ctrl-alt-del
------------
When the value in this file is 0, ctrl-alt-del is trapped and sent to the init
program to handle a graceful restart. However, when the value is greater that
zero, Linux's reaction to this key combination will be an immediate reboot,
without 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 is up to the program to decide what to do with
it.
domainname and hostname
-----------------------
These files can be controlled to set the NIS domainname and hostname of your
box. For the classic darkstar.frop.org a simple:
# echo "darkstar" > /proc/sys/kernel/hostname
# echo "frop.org" > /proc/sys/kernel/domainname
would suffice to set your hostname and NIS domainname.
osrelease, ostype and version
-----------------------------
The names make it pretty obvious what these fields contain:
> cat /proc/sys/kernel/osrelease
2.2.12
> cat /proc/sys/kernel/ostype
Linux
> cat /proc/sys/kernel/version
#4 Fri Oct 1 12:41:14 PDT 1999
The files osrelease and ostype should be clear enough. Version needs a little
more clarification. The #4 means that this is the 4th kernel built from this
source base and the date after it indicates the time the kernel was built. The
only way to tune these values is to rebuild the kernel.
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. If set to 0, the auto reboot after a kernel panic
is disabled, which is the default setting.
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, which come from inside the kernel. See syslog(2) for more
information on the different log levels.
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 the console_loglevel can be set.
default_console_loglevel
------------------------
Default value for console_loglevel.
sg-big-buff
-----------
This file shows the size of the generic SCSI (sg) buffer. At this point, you
can't tune it yet, but you can change it at compile time by editing
include/scsi/sg.h and changing the value of SG_BIG_BUFF.
If you use a scanner with SANE (Scanner Access Now Easy) you might want to set
this to a higher value. Refer to the SANE documentation on this issue.
modprobe
--------
The location where the modprobe binary is located. The kernel uses this
program to load modules on demand.
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.
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.
msgmni
------
Maximum number of message queue ids on the system.
This value scales to the amount of lowmem. It is automatically recomputed
upon memory add/remove or ipc namespace creation/removal.
When a value is written into this file, msgmni's value becomes fixed, i.e. it
is not recomputed anymore when one of the above events occurs.
Use auto_msgmni to change this behavior.
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.
2.4 /proc/sys/vm - The virtual memory subsystem
-----------------------------------------------
Please see: Documentation/sysctls/vm.txt for a description of these
Please see: Documentation/sysctls/ directory for descriptions of these
entries.
------------------------------------------------------------------------------
Summary
------------------------------------------------------------------------------
Certain aspects of kernel behavior can be modified at runtime, without the
need to recompile the kernel, or even to reboot the system. The files in the
/proc/sys tree can not only be read, but also modified. You can use the echo
command to write value into these files, thereby changing the default settings
of the kernel.
------------------------------------------------------------------------------
2.5 /proc/sys/dev - Device specific parameters
----------------------------------------------
Currently there is only support for CDROM drives, and for those, there is only
one read-only file containing information about the CD-ROM drives attached to
the system:
>cat /proc/sys/dev/cdrom/info
CD-ROM information, Id: cdrom.c 2.55 1999/04/25
drive name: sr0 hdb
drive speed: 32 40
drive # of slots: 1 0
Can close tray: 1 1
Can open tray: 1 1
Can lock tray: 1 1
Can change speed: 1 1
Can select disk: 0 1
Can read multisession: 1 1
Can read MCN: 1 1
Reports media changed: 1 1
Can play audio: 1 1
You see two drives, sr0 and hdb, along with a list of their features.
2.6 /proc/sys/sunrpc - Remote procedure calls
---------------------------------------------
This directory contains four files, which enable or disable debugging for the
RPC functions NFS, NFS-daemon, RPC and NLM. The default values are 0. They can
be set to one to turn debugging on. (The default value is 0 for each)
2.7 /proc/sys/net - Networking stuff
------------------------------------
The interface to the networking parts of the kernel is located in
/proc/sys/net. Table 2-3 shows all possible subdirectories. You may see only
some of them, depending on your kernel's configuration.
Table 2-3: Subdirectories in /proc/sys/net
..............................................................................
Directory Content Directory Content
core General parameter appletalk Appletalk protocol
unix Unix domain sockets netrom NET/ROM
802 E802 protocol ax25 AX25
ethernet Ethernet protocol rose X.25 PLP layer
ipv4 IP version 4 x25 X.25 protocol
ipx IPX token-ring IBM token ring
bridge Bridging decnet DEC net
ipv6 IP version 6
..............................................................................
We will concentrate on IP networking here. Since AX15, X.25, and DEC Net are
only minor players in the Linux world, we'll skip them in this chapter. You'll
find some short info on Appletalk and IPX further on in this chapter. Review
the online documentation and the kernel source to get a detailed view of the
parameters for those protocols. In this section we'll discuss the
subdirectories printed in bold letters in the table above. As default values
are suitable for most needs, there is no need to change these values.
/proc/sys/net/core - Network core options
-----------------------------------------
rmem_default
------------
The default setting of the socket receive buffer in bytes.
rmem_max
--------
The maximum receive socket buffer size in bytes.
wmem_default
------------
The default setting (in bytes) of the socket send buffer.
wmem_max
--------
The maximum send socket buffer size in bytes.
message_burst and message_cost
------------------------------
These parameters are used to limit the warning messages written to the kernel
log from the networking code. They enforce a rate limit to make a
denial-of-service attack impossible. A higher message_cost factor, results in
fewer messages that will be written. Message_burst controls when messages will
be dropped. The default settings limit warning messages to one every five
seconds.
warnings
--------
This controls console messages from the networking stack that can occur because
of problems on the network like duplicate address or bad checksums. Normally,
this should be enabled, but if the problem persists the messages can be
disabled.
netdev_budget
-------------
Maximum number of packets taken from all interfaces in one polling cycle (NAPI
poll). In one polling cycle interfaces which are registered to polling are
probed in a round-robin manner. The limit of packets in one such probe can be
set per-device via sysfs class/net/<device>/weight .
netdev_max_backlog
------------------
Maximum number of packets, queued on the INPUT side, when the interface
receives packets faster than kernel can process them.
optmem_max
----------
Maximum ancillary buffer size allowed per socket. Ancillary data is a sequence
of struct cmsghdr structures with appended data.
/proc/sys/net/unix - Parameters for Unix domain sockets
-------------------------------------------------------
There are only two files in this subdirectory. They control the delays for
deleting and destroying socket descriptors.
2.8 /proc/sys/net/ipv4 - IPV4 settings
--------------------------------------
IP version 4 is still the most used protocol in Unix networking. It will be
replaced by IP version 6 in the next couple of years, but for the moment it's
the de facto standard for the internet and is used in most networking
environments around the world. Because of the importance of this protocol,
we'll have a deeper look into the subtree controlling the behavior of the IPv4
subsystem of the Linux kernel.
Let's start with the entries in /proc/sys/net/ipv4.
ICMP settings
-------------
icmp_echo_ignore_all and icmp_echo_ignore_broadcasts
----------------------------------------------------
Turn on (1) or off (0), if the kernel should ignore all ICMP ECHO requests, or
just those to broadcast and multicast addresses.
Please note that if you accept ICMP echo requests with a broadcast/multi\-cast
destination address your network may be used as an exploder for denial of
service packet flooding attacks to other hosts.
icmp_destunreach_rate, icmp_echoreply_rate, icmp_paramprob_rate and icmp_timeexeed_rate
---------------------------------------------------------------------------------------
Sets limits for sending ICMP packets to specific targets. A value of zero
disables all limiting. Any positive value sets the maximum package rate in
hundredth of a second (on Intel systems).
IP settings
-----------
ip_autoconfig
-------------
This file contains the number one if the host received its IP configuration by
RARP, BOOTP, DHCP or a similar mechanism. Otherwise it is zero.
ip_default_ttl
--------------
TTL (Time To Live) for IPv4 interfaces. This is simply the maximum number of
hops a packet may travel.
ip_dynaddr
----------
Enable dynamic socket address rewriting on interface address change. This is
useful for dialup interface with changing IP addresses.
ip_forward
----------
Enable or disable forwarding of IP packages between interfaces. Changing this
value resets all other parameters to their default values. They differ if the
kernel is configured as host or router.
ip_local_port_range
-------------------
Range of ports used by TCP and UDP to choose the local port. Contains two
numbers, the first number is the lowest port, the second number the highest
local port. Default is 1024-4999. Should be changed to 32768-61000 for
high-usage systems.
ip_no_pmtu_disc
---------------
Global switch to turn path MTU discovery off. It can also be set on a per
socket basis by the applications or on a per route basis.
ip_masq_debug
-------------
Enable/disable debugging of IP masquerading.
IP fragmentation settings
-------------------------
ipfrag_high_trash and ipfrag_low_trash
--------------------------------------
Maximum memory used to reassemble IP fragments. When ipfrag_high_thresh bytes
of memory is allocated for this purpose, the fragment handler will toss
packets until ipfrag_low_thresh is reached.
ipfrag_time
-----------
Time in seconds to keep an IP fragment in memory.
TCP settings
------------
tcp_ecn
-------
This file controls the use of the ECN bit in the IPv4 headers. This is a new
feature about Explicit Congestion Notification, but some routers and firewalls
block traffic that has this bit set, so it could be necessary to echo 0 to
/proc/sys/net/ipv4/tcp_ecn if you want to talk to these sites. For more info
you could read RFC2481.
tcp_retrans_collapse
--------------------
Bug-to-bug compatibility with some broken printers. On retransmit, try to send
larger packets to work around bugs in certain TCP stacks. Can be turned off by
setting it to zero.
tcp_keepalive_probes
--------------------
Number of keep alive probes TCP sends out, until it decides that the
connection is broken.
tcp_keepalive_time
------------------
How often TCP sends out keep alive messages, when keep alive is enabled. The
default is 2 hours.
tcp_syn_retries
---------------
Number of times initial SYNs for a TCP connection attempt will be
retransmitted. Should not be higher than 255. This is only the timeout for
outgoing connections, for incoming connections the number of retransmits is
defined by tcp_retries1.
tcp_sack
--------
Enable select acknowledgments after RFC2018.
tcp_timestamps
--------------
Enable timestamps as defined in RFC1323.
tcp_stdurg
----------
Enable the strict RFC793 interpretation of the TCP urgent pointer field. The
default is to use the BSD compatible interpretation of the urgent pointer
pointing to the first byte after the urgent data. The RFC793 interpretation is
to have it point to the last byte of urgent data. Enabling this option may
lead to interoperability problems. Disabled by default.
tcp_syncookies
--------------
Only valid when the kernel was compiled with CONFIG_SYNCOOKIES. Send out
syncookies when the syn backlog queue of a socket overflows. This is to ward
off the common 'syn flood attack'. Disabled by default.
Note that the concept of a socket backlog is abandoned. This means the peer
may not receive reliable error messages from an over loaded server with
syncookies enabled.
tcp_window_scaling
------------------
Enable window scaling as defined in RFC1323.
tcp_fin_timeout
---------------
The length of time in seconds it takes to receive a final FIN before the
socket is always closed. This is strictly a violation of the TCP
specification, but required to prevent denial-of-service attacks.
tcp_max_ka_probes
-----------------
Indicates how many keep alive probes are sent per slow timer run. Should not
be set too high to prevent bursts.
tcp_max_syn_backlog
-------------------
Length of the per socket backlog queue. Since Linux 2.2 the backlog specified
in listen(2) only specifies the length of the backlog queue of already
established sockets. When more connection requests arrive Linux starts to drop
packets. When syncookies are enabled the packets are still answered and the
maximum queue is effectively ignored.
tcp_retries1
------------
Defines how often an answer to a TCP connection request is retransmitted
before giving up.
tcp_retries2
------------
Defines how often a TCP packet is retransmitted before giving up.
Interface specific settings
---------------------------
In the directory /proc/sys/net/ipv4/conf you'll find one subdirectory for each
interface the system knows about and one directory calls all. Changes in the
all subdirectory affect all interfaces, whereas changes in the other
subdirectories affect only one interface. All directories have the same
entries:
accept_redirects
----------------
This switch decides if the kernel accepts ICMP redirect messages or not. The
default is 'yes' if the kernel is configured for a regular host and 'no' for a
router configuration.
accept_source_route
-------------------
Should source routed packages be accepted or declined. The default is
dependent on the kernel configuration. It's 'yes' for routers and 'no' for
hosts.
bootp_relay
~~~~~~~~~~~
Accept packets with source address 0.b.c.d with destinations not to this host
as local ones. It is supposed that a BOOTP relay daemon will catch and forward
such packets.
The default is 0, since this feature is not implemented yet (kernel version
2.2.12).
forwarding
----------
Enable or disable IP forwarding on this interface.
log_martians
------------
Log packets with source addresses with no known route to kernel log.
mc_forwarding
-------------
Do multicast routing. The kernel needs to be compiled with CONFIG_MROUTE and a
multicast routing daemon is required.
proxy_arp
---------
Does (1) or does not (0) perform proxy ARP.
rp_filter
---------
Integer value determines if a source validation should be made. 1 means yes, 0
means no. Disabled by default, but local/broadcast address spoofing is always
on.
If you set this to 1 on a router that is the only connection for a network to
the net, it will prevent spoofing attacks against your internal networks
(external addresses can still be spoofed), without the need for additional
firewall rules.
secure_redirects
----------------
Accept ICMP redirect messages only for gateways, listed in default gateway
list. Enabled by default.
shared_media
------------
If it is not set the kernel does not assume that different subnets on this
device can communicate directly. Default setting is 'yes'.
send_redirects
--------------
Determines whether to send ICMP redirects to other hosts.
Routing settings
----------------
The directory /proc/sys/net/ipv4/route contains several file to control
routing issues.
error_burst and error_cost
--------------------------
These parameters are used to limit how many ICMP destination unreachable to
send from the host in question. ICMP destination unreachable messages are
sent when we cannot reach the next hop while trying to transmit a packet.
It will also print some error messages to kernel logs if someone is ignoring
our ICMP redirects. The higher the error_cost factor is, the fewer
destination unreachable and error messages will be let through. Error_burst
controls when destination unreachable messages and error messages will be
dropped. The default settings limit warning messages to five every second.
flush
-----
Writing to this file results in a flush of the routing cache.
gc_elasticity, gc_interval, gc_min_interval_ms, gc_timeout, gc_thresh
---------------------------------------------------------------------
Values to control the frequency and behavior of the garbage collection
algorithm for the routing cache. gc_min_interval is deprecated and replaced
by gc_min_interval_ms.
max_size
--------
Maximum size of the routing cache. Old entries will be purged once the cache
reached has this size.
redirect_load, redirect_number
------------------------------
Factors which determine if more ICPM redirects should be sent to a specific
host. No redirects will be sent once the load limit or the maximum number of
redirects has been reached.
redirect_silence
----------------
Timeout for redirects. After this period redirects will be sent again, even if
this has been stopped, because the load or number limit has been reached.
Network Neighbor handling
-------------------------
Settings about how to handle connections with direct neighbors (nodes attached
to the same link) can be found in the directory /proc/sys/net/ipv4/neigh.
As we saw it in the conf directory, there is a default subdirectory which
holds the default values, and one directory for each interface. The contents
of the directories are identical, with the single exception that the default
settings contain additional options to set garbage collection parameters.
In the interface directories you'll find the following entries:
base_reachable_time, base_reachable_time_ms
-------------------------------------------
A base value used for computing the random reachable time value as specified
in RFC2461.
Expression of base_reachable_time, which is deprecated, is in seconds.
Expression of base_reachable_time_ms is in milliseconds.
retrans_time, retrans_time_ms
-----------------------------
The time between retransmitted Neighbor Solicitation messages.
Used for address resolution and to determine if a neighbor is
unreachable.
Expression of retrans_time, which is deprecated, is in 1/100 seconds (for
IPv4) or in jiffies (for IPv6).
Expression of retrans_time_ms is in milliseconds.
unres_qlen
----------
Maximum queue length for a pending arp request - the number of packets which
are accepted from other layers while the ARP address is still resolved.
anycast_delay
-------------
Maximum for random delay of answers to neighbor solicitation messages in
jiffies (1/100 sec). Not yet implemented (Linux does not have anycast support
yet).
ucast_solicit
-------------
Maximum number of retries for unicast solicitation.
mcast_solicit
-------------
Maximum number of retries for multicast solicitation.
delay_first_probe_time
----------------------
Delay for the first time probe if the neighbor is reachable. (see
gc_stale_time)
locktime
--------
An ARP/neighbor entry is only replaced with a new one if the old is at least
locktime old. This prevents ARP cache thrashing.
proxy_delay
-----------
Maximum time (real time is random [0..proxytime]) before answering to an ARP
request for which we have an proxy ARP entry. In some cases, this is used to
prevent network flooding.
proxy_qlen
----------
Maximum queue length of the delayed proxy arp timer. (see proxy_delay).
app_solicit
----------
Determines the number of requests to send to the user level ARP daemon. Use 0
to turn off.
gc_stale_time
-------------
Determines how often to check for stale ARP entries. After an ARP entry is
stale it will be resolved again (which is useful when an IP address migrates
to another machine). When ucast_solicit is greater than 0 it first tries to
send an ARP packet directly to the known host When that fails and
mcast_solicit is greater than 0, an ARP request is broadcasted.
2.9 Appletalk
-------------
The /proc/sys/net/appletalk directory holds the Appletalk configuration data
when Appletalk is loaded. The configurable parameters are:
aarp-expiry-time
----------------
The amount of time we keep an ARP entry before expiring it. Used to age out
old hosts.
aarp-resolve-time
-----------------
The amount of time we will spend trying to resolve an Appletalk address.
aarp-retransmit-limit
---------------------
The number of times we will retransmit a query before giving up.
aarp-tick-time
--------------
Controls the rate at which expires are checked.
The directory /proc/net/appletalk holds the list of active Appletalk sockets
on a machine.
The fields indicate the DDP type, the local address (in network:node format)
the remote address, the size of the transmit pending queue, the size of the
received queue (bytes waiting for applications to read) the state and the uid
owning the socket.
/proc/net/atalk_iface lists all the interfaces configured for appletalk.It
shows the name of the interface, its Appletalk address, the network range on
that address (or network number for phase 1 networks), and the status of the
interface.
/proc/net/atalk_route lists each known network route. It lists the target
(network) that the route leads to, the router (may be directly connected), the
route flags, and the device the route is using.
2.10 IPX
--------
The IPX protocol has no tunable values in proc/sys/net.
The IPX protocol does, however, provide proc/net/ipx. This lists each IPX
socket giving the local and remote addresses in Novell format (that is
network:node:port). In accordance with the strange Novell tradition,
everything but the port is in hex. Not_Connected is displayed for sockets that
are not tied to a specific remote address. The Tx and Rx queue sizes indicate
the number of bytes pending for transmission and reception. The state
indicates the state the socket is in and the uid is the owning uid of the
socket.
The /proc/net/ipx_interface file lists all IPX interfaces. For each interface
it gives the network number, the node number, and indicates if the network is
the primary network. It also indicates which device it is bound to (or
Internal for internal networks) and the Frame Type if appropriate. Linux
supports 802.3, 802.2, 802.2 SNAP and DIX (Blue Book) ethernet framing for
IPX.
The /proc/net/ipx_route table holds a list of IPX routes. For each route it
gives the destination network, the router node (or Directly) and the network
address of the router (or Connected) for internal networks.
2.11 /proc/sys/fs/mqueue - POSIX message queues filesystem
----------------------------------------------------------
The "mqueue" filesystem provides the necessary kernel features to enable the
creation of a user space library that implements the POSIX message queues
API (as noted by the MSG tag in the POSIX 1003.1-2001 version of the System
Interfaces specification.)
The "mqueue" filesystem contains values for determining/setting the amount of
resources used by the file system.
/proc/sys/fs/mqueue/queues_max is a read/write file for setting/getting the
maximum number of message queues allowed on the system.
/proc/sys/fs/mqueue/msg_max is a read/write file for setting/getting the
maximum number of messages in a queue value. In fact it is the limiting value
for another (user) limit which is set in mq_open invocation. This attribute of
a queue must be less or equal then msg_max.
/proc/sys/fs/mqueue/msgsize_max is a read/write file for setting/getting the
maximum message size value (it is every message queue's attribute set during
its creation).
------------------------------------------------------------------------------
CHAPTER 3: PER-PROCESS PARAMETERS
------------------------------------------------------------------------------
2.12 /proc/<pid>/oom_adj - Adjust the oom-killer score
3.1 /proc/<pid>/oom_adj - Adjust the oom-killer score
------------------------------------------------------
This file can be used to adjust the score used to select which processes
......@@ -2041,25 +1037,15 @@ The task with the highest badness score is then selected and its children
are killed, process itself will be killed in an OOM situation when it does
not have children or some of them disabled oom like described above.
2.13 /proc/<pid>/oom_score - Display current oom-killer score
3.2 /proc/<pid>/oom_score - Display current oom-killer score
-------------------------------------------------------------
------------------------------------------------------------------------------
This file can be used to check the current score used by the oom-killer is for
any given <pid>. Use it together with /proc/<pid>/oom_adj to tune which
process should be killed in an out-of-memory situation.
------------------------------------------------------------------------------
Summary
------------------------------------------------------------------------------
Certain aspects of kernel behavior can be modified at runtime, without the
need to recompile the kernel, or even to reboot the system. The files in the
/proc/sys tree can not only be read, but also modified. You can use the echo
command to write value into these files, thereby changing the default settings
of the kernel.
------------------------------------------------------------------------------
2.14 /proc/<pid>/io - Display the IO accounting fields
3.3 /proc/<pid>/io - Display the IO accounting fields
-------------------------------------------------------
This file contains IO statistics for each running process
......@@ -2161,7 +1147,7 @@ those 64-bit counters, process A could see an intermediate result.
More information about this can be found within the taskstats documentation in
Documentation/accounting.
2.15 /proc/<pid>/coredump_filter - Core dump filtering settings
3.4 /proc/<pid>/coredump_filter - Core dump filtering settings
---------------------------------------------------------------
When a process is dumped, all anonymous memory is written to a core file as
long as the size of the core file isn't limited. But sometimes we don't want
......@@ -2205,7 +1191,7 @@ For example:
$ echo 0x7 > /proc/self/coredump_filter
$ ./some_program
2.16 /proc/<pid>/mountinfo - Information about mounts
3.5 /proc/<pid>/mountinfo - Information about mounts
--------------------------------------------------------
This file contains lines of the form:
......@@ -2242,30 +1228,3 @@ For more information on mount propagation see:
Documentation/filesystems/sharedsubtree.txt
2.17 /proc/sys/fs/epoll - Configuration options for the epoll interface
--------------------------------------------------------
This directory contains configuration options for the epoll(7) interface.
max_user_instances
------------------
This is the maximum number of epoll file descriptors that a single user can
have open at a given time. The default value is 128, and should be enough
for normal users.
max_user_watches
----------------
Every epoll file descriptor can store a number of files to be monitored
for event readiness. Each one of these monitored files constitutes a "watch".
This configuration option sets the maximum number of "watches" that are
allowed for each user.
Each "watch" costs roughly 90 bytes on a 32bit kernel, and roughly 160 bytes
on a 64bit one.
The current default value for max_user_watches is the 1/32 of the available
low memory, divided for the "watch" cost in bytes.
------------------------------------------------------------------------------
Documentation/sysctl/00-INDEX
View file @ 760df93e
......@@ -10,6 +10,8 @@ fs.txt
- documentation for /proc/sys/fs/*.
kernel.txt
- documentation for /proc/sys/kernel/*.
net.txt
- documentation for /proc/sys/net/*.
sunrpc.txt
- documentation for /proc/sys/sunrpc/*.
vm.txt
......
Documentation/sysctl/fs.txt
View file @ 760df93e
Documentation for /proc/sys/fs/* 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.
......@@ -14,7 +15,12 @@ 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.
1. /proc/sys/fs
----------------------------------------------------------
Currently, these files are in /proc/sys/fs:
- aio-max-nr
- aio-nr
- dentry-state
- dquot-max
- dquot-nr
......@@ -30,8 +36,15 @@ Currently, these files are in /proc/sys/fs:
- super-max
- super-nr
Documentation for the files in /proc/sys/fs/binfmt_misc is
in Documentation/binfmt_misc.txt.
==============================================================
aio-nr & aio-max-nr:
aio-nr is the running total of the number of events specified on the
io_setup system call for all currently active aio contexts. If aio-nr
reaches aio-max-nr then io_setup will fail with EAGAIN. Note that
raising aio-max-nr does not result in the pre-allocation or re-sizing
of any kernel data structures.
==============================================================
......@@ -178,3 +191,60 @@ requests. aio-max-nr allows you to change the maximum value
aio-nr can grow to.
==============================================================
2. /proc/sys/fs/binfmt_misc
----------------------------------------------------------
Documentation for the files in /proc/sys/fs/binfmt_misc is
in Documentation/binfmt_misc.txt.
3. /proc/sys/fs/mqueue - POSIX message queues filesystem
----------------------------------------------------------
The "mqueue" filesystem provides the necessary kernel features to enable the
creation of a user space library that implements the POSIX message queues
API (as noted by the MSG tag in the POSIX 1003.1-2001 version of the System
Interfaces specification.)
The "mqueue" filesystem contains values for determining/setting the amount of
resources used by the file system.
/proc/sys/fs/mqueue/queues_max is a read/write file for setting/getting the
maximum number of message queues allowed on the system.
/proc/sys/fs/mqueue/msg_max is a read/write file for setting/getting the
maximum number of messages in a queue value. In fact it is the limiting value
for another (user) limit which is set in mq_open invocation. This attribute of
a queue must be less or equal then msg_max.
/proc/sys/fs/mqueue/msgsize_max is a read/write file for setting/getting the
maximum message size value (it is every message queue's attribute set during
its creation).
4. /proc/sys/fs/epoll - Configuration options for the epoll interface
--------------------------------------------------------
This directory contains configuration options for the epoll(7) interface.
max_user_instances
------------------
This is the maximum number of epoll file descriptors that a single user can
have open at a given time. The default value is 128, and should be enough
for normal users.
max_user_watches
----------------
Every epoll file descriptor can store a number of files to be monitored
for event readiness. Each one of these monitored files constitutes a "watch".
This configuration option sets the maximum number of "watches" that are
allowed for each user.
Each "watch" costs roughly 90 bytes on a 32bit kernel, and roughly 160 bytes
on a 64bit one.
The current default value for max_user_watches is the 1/32 of the available
low memory, divided for the "watch" cost in bytes.
Documentation/sysctl/kernel.txt
View file @ 760df93e
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.
......@@ -18,6 +19,7 @@ Currently, these files might (depending on your configuration)
show up in /proc/sys/kernel:
- acpi_video_flags
- acct
- auto_msgmni
- core_pattern
- core_uses_pid
- ctrl-alt-del
......@@ -33,6 +35,7 @@ show up in /proc/sys/kernel:
- msgmax
- msgmnb
- msgmni
- nmi_watchdog
- osrelease
- ostype
- overflowgid
......@@ -40,6 +43,7 @@ show up in /proc/sys/kernel:
- panic
- pid_max
- powersave-nap [ PPC only ]
- panic_on_unrecovered_nmi
- printk
- randomize_va_space
- real-root-dev ==> Documentation/initrd.txt
......@@ -55,6 +59,7 @@ show up in /proc/sys/kernel:
- sysrq ==> Documentation/sysrq.txt
- tainted
- threads-max
- unknown_nmi_panic
- version
==============================================================
......@@ -381,3 +386,51 @@ can be ORed together:
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.
Documentation/sysctl/net.txt 0 → 100644
View file @ 760df93e
Documentation for /proc/sys/net/* kernel version 2.4.0-test11-pre4
(c) 1999 Terrehon Bowden <terrehon@pacbell.net>
Bodo Bauer <bb@ricochet.net>
(c) 2000 Jorge Nerin <comandante@zaralinux.com>
(c) 2009 Shen Feng <shen@cn.fujitsu.com>
For general info and legal blurb, please look in README.
==============================================================
This file contains the documentation for the sysctl files in
/proc/sys/net and is valid for Linux kernel version 2.4.0-test11-pre4.
The interface to the networking parts of the kernel is located in
/proc/sys/net. The following table shows all possible subdirectories.You may
see only some of them, depending on your kernel's configuration.
Table : Subdirectories in /proc/sys/net
..............................................................................
Directory Content Directory Content
core General parameter appletalk Appletalk protocol
unix Unix domain sockets netrom NET/ROM
802 E802 protocol ax25 AX25
ethernet Ethernet protocol rose X.25 PLP layer
ipv4 IP version 4 x25 X.25 protocol
ipx IPX token-ring IBM token ring
bridge Bridging decnet DEC net
ipv6 IP version 6
..............................................................................
1. /proc/sys/net/core - Network core options
-------------------------------------------------------
rmem_default
------------
The default setting of the socket receive buffer in bytes.
rmem_max
--------
The maximum receive socket buffer size in bytes.
wmem_default
------------
The default setting (in bytes) of the socket send buffer.
wmem_max
--------
The maximum send socket buffer size in bytes.
message_burst and message_cost
------------------------------
These parameters are used to limit the warning messages written to the kernel
log from the networking code. They enforce a rate limit to make a
denial-of-service attack impossible. A higher message_cost factor, results in
fewer messages that will be written. Message_burst controls when messages will
be dropped. The default settings limit warning messages to one every five
seconds.
warnings
--------
This controls console messages from the networking stack that can occur because
of problems on the network like duplicate address or bad checksums. Normally,
this should be enabled, but if the problem persists the messages can be
disabled.
netdev_budget
-------------
Maximum number of packets taken from all interfaces in one polling cycle (NAPI
poll). In one polling cycle interfaces which are registered to polling are
probed in a round-robin manner. The limit of packets in one such probe can be
set per-device via sysfs class/net/<device>/weight .
netdev_max_backlog
------------------
Maximum number of packets, queued on the INPUT side, when the interface
receives packets faster than kernel can process them.
optmem_max
----------
Maximum ancillary buffer size allowed per socket. Ancillary data is a sequence
of struct cmsghdr structures with appended data.
2. /proc/sys/net/unix - Parameters for Unix domain sockets
-------------------------------------------------------
There are only two files in this subdirectory. They control the delays for
deleting and destroying socket descriptors.
3. /proc/sys/net/ipv4 - IPV4 settings
-------------------------------------------------------
Please see: Documentation/networking/ip-sysctl.txt and ipvs-sysctl.txt for
descriptions of these entries.
4. Appletalk
-------------------------------------------------------
The /proc/sys/net/appletalk directory holds the Appletalk configuration data
when Appletalk is loaded. The configurable parameters are:
aarp-expiry-time
----------------
The amount of time we keep an ARP entry before expiring it. Used to age out
old hosts.
aarp-resolve-time
-----------------
The amount of time we will spend trying to resolve an Appletalk address.
aarp-retransmit-limit
---------------------
The number of times we will retransmit a query before giving up.
aarp-tick-time
--------------
Controls the rate at which expires are checked.
The directory /proc/net/appletalk holds the list of active Appletalk sockets
on a machine.
The fields indicate the DDP type, the local address (in network:node format)
the remote address, the size of the transmit pending queue, the size of the
received queue (bytes waiting for applications to read) the state and the uid
owning the socket.
/proc/net/atalk_iface lists all the interfaces configured for appletalk.It
shows the name of the interface, its Appletalk address, the network range on
that address (or network number for phase 1 networks), and the status of the
interface.
/proc/net/atalk_route lists each known network route. It lists the target
(network) that the route leads to, the router (may be directly connected), the
route flags, and the device the route is using.
5. IPX
-------------------------------------------------------
The IPX protocol has no tunable values in proc/sys/net.
The IPX protocol does, however, provide proc/net/ipx. This lists each IPX
socket giving the local and remote addresses in Novell format (that is
network:node:port). In accordance with the strange Novell tradition,
everything but the port is in hex. Not_Connected is displayed for sockets that
are not tied to a specific remote address. The Tx and Rx queue sizes indicate
the number of bytes pending for transmission and reception. The state
indicates the state the socket is in and the uid is the owning uid of the
socket.
The /proc/net/ipx_interface file lists all IPX interfaces. For each interface
it gives the network number, the node number, and indicates if the network is
the primary network. It also indicates which device it is bound to (or
Internal for internal networks) and the Frame Type if appropriate. Linux
supports 802.3, 802.2, 802.2 SNAP and DIX (Blue Book) ethernet framing for
IPX.
The /proc/net/ipx_route table holds a list of IPX routes. For each route it
gives the destination network, the router node (or Directly) and the network
address of the router (or Connected) for internal networks.
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