-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
------------------------------------------------
-
-The files in this directory can be used to tune the operation of the virtual
-memory (VM) subsystem of the Linux kernel.
-
-vfs_cache_pressure
-------------------
-
-Controls the tendency of the kernel to reclaim the memory which is used for
-caching of directory and inode objects.
-
-At the default value of vfs_cache_pressure=100 the kernel will attempt to
-reclaim dentries and inodes at a "fair" rate with respect to pagecache and
-swapcache reclaim. Decreasing vfs_cache_pressure causes the kernel to prefer
-to retain dentry and inode caches. Increasing vfs_cache_pressure beyond 100
-causes the kernel to prefer to reclaim dentries and inodes.
-
-dirty_background_ratio
-----------------------
-
-Contains, as a percentage of the dirtyable system memory (free pages + mapped
-pages + file cache, not including locked pages and HugePages), the number of
-pages at which the pdflush background writeback daemon will start writing out
-dirty data.
-
-dirty_ratio
------------------
-
-Contains, as a percentage of the dirtyable system memory (free pages + mapped
-pages + file cache, not including locked pages and HugePages), the number of
-pages at which a process which is generating disk writes will itself start
-writing out dirty data.
-
-dirty_writeback_centisecs
--------------------------
-
-The pdflush writeback daemons will periodically wake up and write `old' data
-out to disk. This tunable expresses the interval between those wakeups, in
-100'ths of a second.
-
-Setting this to zero disables periodic writeback altogether.
-
-dirty_expire_centisecs
-----------------------
-
-This tunable is used to define when dirty data is old enough to be eligible
-for writeout by the pdflush daemons. It is expressed in 100'ths of a second.
-Data which has been dirty in-memory for longer than this interval will be
-written out next time a pdflush daemon wakes up.
-
-highmem_is_dirtyable
---------------------
-
-Only present if CONFIG_HIGHMEM is set.
-
-This defaults to 0 (false), meaning that the ratios set above are calculated
-as a percentage of lowmem only. This protects against excessive scanning
-in page reclaim, swapping and general VM distress.
-
-Setting this to 1 can be useful on 32 bit machines where you want to make
-random changes within an MMAPed file that is larger than your available
-lowmem without causing large quantities of random IO. Is is safe if the
-behavior of all programs running on the machine is known and memory will
-not be otherwise stressed.
-
-legacy_va_layout
-----------------
-
-If non-zero, this sysctl disables the new 32-bit mmap mmap layout - the kernel
-will use the legacy (2.4) layout for all processes.
-
-lowmem_reserve_ratio
----------------------
-
-For some specialised workloads on highmem machines it is dangerous for
-the kernel to allow process memory to be allocated from the "lowmem"
-zone. This is because that memory could then be pinned via the mlock()
-system call, or by unavailability of swapspace.
-
-And on large highmem machines this lack of reclaimable lowmem memory
-can be fatal.
-
-So the Linux page allocator has a mechanism which prevents allocations
-which _could_ use highmem from using too much lowmem. This means that
-a certain amount of lowmem is defended from the possibility of being
-captured into pinned user memory.
-
-(The same argument applies to the old 16 megabyte ISA DMA region. This
-mechanism will also defend that region from allocations which could use
-highmem or lowmem).
-
-The `lowmem_reserve_ratio' tunable determines how aggressive the kernel is
-in defending these lower zones.
-
-If you have a machine which uses highmem or ISA DMA and your
-applications are using mlock(), or if you are running with no swap then
-you probably should change the lowmem_reserve_ratio setting.
-
-The lowmem_reserve_ratio is an array. You can see them by reading this file.
--
-% cat /proc/sys/vm/lowmem_reserve_ratio
-256 256 32
--
-Note: # of this elements is one fewer than number of zones. Because the highest
- zone's value is not necessary for following calculation.
-
-But, these values are not used directly. The kernel calculates # of protection
-pages for each zones from them. These are shown as array of protection pages
-in /proc/zoneinfo like followings. (This is an example of x86-64 box).
-Each zone has an array of protection pages like this.
-
--
-Node 0, zone DMA
- pages free 1355
- min 3
- low 3
- high 4
- :
- :
- numa_other 0
- protection: (0, 2004, 2004, 2004)
- ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
- pagesets
- cpu: 0 pcp: 0
- :
--
-These protections are added to score to judge whether this zone should be used
-for page allocation or should be reclaimed.
-
-In this example, if normal pages (index=2) are required to this DMA zone and
-pages_high is used for watermark, the kernel judges this zone should not be
-used because pages_free(1355) is smaller than watermark + protection[2]
-(4 + 2004 = 2008). If this protection value is 0, this zone would be used for
-normal page requirement. If requirement is DMA zone(index=0), protection[0]
-(=0) is used.
-
-zone[i]'s protection[j] is calculated by following expression.
-
-(i < j):
- zone[i]->protection[j]
- = (total sums of present_pages from zone[i+1] to zone[j] on the node)
- / lowmem_reserve_ratio[i];
-(i = j):
- (should not be protected. = 0;
-(i > j):
- (not necessary, but looks 0)
-
-The default values of lowmem_reserve_ratio[i] are
- 256 (if zone[i] means DMA or DMA32 zone)
- 32 (others).
-As above expression, they are reciprocal number of ratio.
-256 means 1/256. # of protection pages becomes about "0.39%" of total present
-pages of higher zones on the node.
-
-If you would like to protect more pages, smaller values are effective.
-The minimum value is 1 (1/1 -> 100%).
-
-page-cluster
-------------
-
-page-cluster controls the number of pages which are written to swap in
-a single attempt. The swap I/O size.
-
-It is a logarithmic value - setting it to zero means "1 page", setting
-it to 1 means "2 pages", setting it to 2 means "4 pages", etc.
-
-The default value is three (eight pages at a time). There may be some
-small benefits in tuning this to a different value if your workload is
-swap-intensive.
-
-overcommit_memory
------------------
-
-Controls overcommit of system memory, possibly allowing processes
-to allocate (but not use) more memory than is actually available.
-
-
-0 - Heuristic overcommit handling. Obvious overcommits of
- address space are refused. Used for a typical system. It
- ensures a seriously wild allocation fails while allowing
- overcommit to reduce swap usage. root is allowed to
- allocate slightly more memory in this mode. This is the
- default.
-
-1 - Always overcommit. Appropriate for some scientific
- applications.
-
-2 - Don't overcommit. The total address space commit
- for the system is not permitted to exceed swap plus a
- configurable percentage (default is 50) of physical RAM.
- Depending on the percentage you use, in most situations
- this means a process will not be killed while attempting
- to use already-allocated memory but will receive errors
- on memory allocation as appropriate.
-
-overcommit_ratio
-----------------
-
-Percentage of physical memory size to include in overcommit calculations
-(see above.)
-
-Memory allocation limit = swapspace + physmem * (overcommit_ratio / 100)
-
- swapspace = total size of all swap areas
- physmem = size of physical memory in system
-
-nr_hugepages and hugetlb_shm_group
-----------------------------------
-
-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.
-
-hugepages_treat_as_movable
---------------------------
-
-This parameter is only useful when kernelcore= is specified at boot time to
-create ZONE_MOVABLE for pages that may be reclaimed or migrated. Huge pages
-are not movable so are not normally allocated from ZONE_MOVABLE. A non-zero
-value written to hugepages_treat_as_movable allows huge pages to be allocated
-from ZONE_MOVABLE.
-
-Once enabled, the ZONE_MOVABLE is treated as an area of memory the huge
-pages pool can easily grow or shrink within. Assuming that applications are
-not running that mlock() a lot of memory, it is likely the huge pages pool
-can grow to the size of ZONE_MOVABLE by repeatedly entering the desired value
-into nr_hugepages and triggering page reclaim.
-
-laptop_mode
------------
-
-laptop_mode is a knob that controls "laptop mode". All the things that are
-controlled by this knob are discussed in Documentation/laptops/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/laptops/laptop-mode.txt.
-
-swap_token_timeout
-------------------
-
-This file contains valid hold time of swap out protection token. The Linux
-VM has token based thrashing control mechanism and uses the token to prevent
-unnecessary page faults in thrashing situation. The unit of the value is
-second. The value would be useful to tune thrashing behavior.
-
-drop_caches
------------
-
-Writing to this will cause the kernel to drop clean caches, dentries and
-inodes from memory, causing that memory to become free.
-
-To free pagecache:
- echo 1 > /proc/sys/vm/drop_caches
-To free dentries and inodes:
- echo 2 > /proc/sys/vm/drop_caches
-To free pagecache, dentries and inodes:
- echo 3 > /proc/sys/vm/drop_caches
-
-As this is a non-destructive operation and dirty objects are not freeable, the
-user should run `sync' first.
-
-
-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_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.