proc.txt

来自「Linux Kernel 2.6.9 for OMAP1710」· 文本 代码 · 共 1,564 行 · 第 1/5 页

----------------------------------

nr_hugepages configures number of hugetlb page reserved for the system.

hugetlb_shm_group contains group id that is allowed to create SysV shared
memory segment using hugetlb page.

laptop_mode
-----------

laptop_mode is a knob that controls "laptop mode". All the things that are
controlled by this knob are discussed in Documentation/laptop-mode.txt.

block_dump
----------

block_dump enables block I/O debugging when set to a nonzero value. More
information on block I/O debugging is in Documentation/laptop-mode.txt.

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.

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 trafic 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 this 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 interoperatibility 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 t