JR中的FTP页面用的就是这个,特点是:
Crossbrowser JavaScript 树(类似于Windows浏览器),目前可以在Mozilla 和
IE中运行。可以重命名节点;拖放操作;用键盘来导航;排序。易于使用。
另外代码的结构也很不错,扩展附加的属性很方便,自定义点击菜单项的操作也很容易。
JR中的FTP页面用的就是这个,特点是:
Crossbrowser JavaScript 树(类似于Windows浏览器),目前可以在Mozilla 和
IE中运行。可以重命名节点;拖放操作;用键盘来导航;排序。易于使用。
另外代码的结构也很不错,扩展附加的属性很方便,自定义点击菜单项的操作也很容易。
在进行java开发的时候多线程问题很多时候似乎是无法避免的,而为了符合多线程的要求,我们往往要使用同步技术,而同步不光会大大的降低系统的性能,更
要命的是可能会出现死锁,而死锁的偶发性导致死锁问题难于追踪调试,当然也有一些解决死锁问题的技术,但是都难于使用,其实很多时候我们可以通过修改设计
来进行避免,设计时考虑的一个最有效而且简单的方法就是编写无状态的类,如果需要状态,那么这些有状态的类可以通过ThreadLocal进行管理,达到
线程安全并且复用的目的。无状态类的比较典型的例子就是spring中通过回调技术实现的数据持久层模板类。
最后需要说明的是,多线程问题不可能完全避免,但是在很多情况下是可以避免的。
今天想给blog加一个全部访问数的统计数,看了一下代码,实际是有这个功能的,但是velocity的模板中是不显示这个数目的,可能是因为有bug,
因为对于blog的站点的引用计数分当天和总计,但是总计的值远远小于实际的值,可能以前的一些值丢失了,还没有找到是什么地方的bug。修改
velocity的模板显示总的访问量比较简单,找哪个地方丢失了计数比较困难,因为保存哪个计数值的代码竟然有七八处。
今天在做关于代码覆盖工具的调研的过程中看了一些英文和中文的资料,也看到了另外的一些内容,例如使用JUnitDoclet加快测试开发,
马上就心动,下载了一个,然后又查看了一下相关的内容,结果发现不光是JUnitDoclet已经有好几年没有更新了,其它的也没有更新的类似工具了,冷
静下来想想,现在使用JUnit做测试一般都是采用的测试驱动或者测试先行,那个时候还没有目标类,怎么自动生成测试骨架呢?这个可能是单元测试代码生成
工具没有发展起来的原因吧。
不要轻易激动,很多想法在第一时间可能会很诱人,但是冷静下来后就会发现其实有很多的不足,你需要充分的考虑前后条件,如果是你想做什么东西的话,先估计一下需要多长的时间做出来,你对相关的技术是否熟悉。
这个也是大学时代的作品,也贴过来了。
谈到重建,大家都有一种摸不着头脑的感觉,原因是内核选项给
人实在太多的无赖,不光需要知道那一项是干什么的,还要知道
自己的硬件到底是什么样的。下面的解说只是给大家作一个参
考,别人领进门,修行在个人,能否配置好自己的内核,做到全
面而短小,这全要靠自己。有一点是要提醒大家的:内核的配置
是一件很考验人的意志的任务,不要因为几次失败而放弃!笔者
也曾经经历过那段难熬的岁月,所以提醒大家–不要气馁。
prompt for development and/or incomplete code/drivers
很多参考书上说这是那些开发人员认为还不是很稳定的功能,但
是根据我的经验,这个是应该选的一个选项,因为现代的LINUX是
建立在这些基础上的,所以应该可以回答Y,除非你只是想使用
LINUX中已经完全定型的东西,但性能肯定不会好到哪,而且对系
统特性的支持也不会好。
processor family (386,486/cx486,586/k5/5×86/6×86,pentinum/k6/tsc,
ppro/6×86)
这应该没有太多可说的吧,选择你的CPU的种类,BIOS可以自检得
到,注意系统的启动信息。需要注意的是不能选择比你的CPU类型
还高级的CPU,否则可能不能正常工作。
math emulation
模拟数学协处理器,如果你的机器没有数学协处理器,那就选上
以提高性能,但486以后数学协处理器就集成到CPU内部了,应该是
用不上的,所以一般的选择是N。当然选上也不会有什么问题,除
了内核稍稍变大外。
mttr(memory type range register) support
这个选项是用来启动pentinum pro和pentinum II 的特殊功能,如果你用
的不是这类CPU就选N,否则也仅仅是使内核变大而已。
symmetric multi-processing support
同步处理器支持,如果你有多个CPU就选上吧。
enable loadable module support
这会启动动态载入额外模块的功能,所以一定选上。
set version information on all symbols for modules
这个选项可以为某个版本的内核而编译的模块在另一个版本的内
核下使用,但一般用不上。
kernel module loader
如果你启用这个选项,你可以通过kerneld程序的帮助在需要的时候
自动载入或卸载那些可载入式的模块。建议选上。
networking support
如果你用到任何网络就应该选上
pci bios support
这个一般是应该选上的,除非你用没有任何PCI设备的机器。PCI
BIOS是用来侦测并启用PCI设备的。
pci bridge optimization(v1.3)
当这个选项被启动时,操作系统会对从CPU和系统内存在PCI总线
来往的数据做最佳化,这个功能已经完成实验阶段,使用起来应
该很安全,而且还可增进系统的效率。
system v ipc
起用这个选项可以使内核支持System V 的进程间通信的功能
(IPC),有些从System V转移过来的程序会需要这个功能,建议启
用该功能。
sysctl support
除非你的内存少的可怜,否则你应该启动这个功能,启用该选项
后内核会大8K,但能让你直接改变内核的参数而不必重新开机。
kernel support for elf binaries
该选项让你的系统得以执行用ELF格式存储的可执行文件,而ELF
是现代LINUX的可执行文件、目标文件和系统函数库的标准格式。
当操作系统要和编译器以及连接器合作时会需要这些标准,所以
应该回答Y。
compile kernel as elf
这选项让你的内核本身以ELF的格式编译,如果你的系统上的过程
gcc默认产生ELF格式的可执行文件,那么你就应该启动这个选项。
先看看你的编译器的版本再决定。
parallel port support
如果你有任何并行口的设备并且想让LINUX使用,那么就可以启用
这个选项。LINUX不仅可以使用并口的打印机,还可以支持PLIP
(一种为并行口而设计的网络通讯协定),ZIP磁盘驱动器、扫描
仪等。在大多情况下,你需要额外的驱动程序才能使用外接的并
口设备。
plug and play support
支持PNP设备并非Microsoft的专利,如果你要让LINUX也支持PNP设
备,只要启用该选项就可以,但有些情况下会和其他设备产生冲
突(I/O,DMA,IRQ等)。这个选项对PCI设备没有影响,因为他们
天生就是PNP设备。
normal floppy disk support
除非你不想在LINUX下使用软盘,否则就应该回答Y。但对于一些
不需要支持软盘驱动器的系统而言,这个选项可以节省一些内
存。
enhanced ide/mfm/dll disk support
除非你不需要MFM/DLL/IDE硬盘的的支持,否则就应该回答Y,但如
果你只有SCSI的硬盘,关掉这个选项会比较安全。
enhanced ide/mfm/dll cdrom support
和上面的类似,只不过是对CDROM的支持而已。
enhanced ide/mfm/dll tape support
一般没有多少人在用磁带机吧,所以回答N是比较好的答案。
enhanced ide/mfm/dll floppy support
这个设备好象一般也没有人用,所以也可以回答N。
xt harddisk support
如果你有这种石器时代的XT硬盘,那么恭喜你你可以用上他了。
parallel port ide device support
LINUX是支持这种很新的并口的IDE设备的,如果你有的话就用上
吧。
networking options
如果你在前面选了支持网络的话,在这里会回答很多问题。除非
你有特别的需求,否则使用默认的选项应该就足够了。
scsi support
如果你有任何一种SCSI控制卡,这个选项就应该回答Y。事先搞清
楚你的硬件的类型,因为这些问题都是针对特定的SCSI控制芯片和
控制卡的,如果你不确定自己使用的是哪一种,查看你的硬件的
说明文件或者LINUX的HOWTO文档。同样也会让你回答很多SCSI设
备的支持(硬盘、CDROM、Tape、floppy等),依据你的情况选择。
如果你没有SCSI设备的话,建议不要支持,因为这会节约很多内核
空间。
network device support
这里面有很多关于网络控制卡的问题,如果你无法确定如何正确
选择,查看硬件文档或LINUX HOWTO文档。
amateur radio support
这个选项可以用来启动无线网络的基本支持,目前的无线网络可
以通过公众频率传输数据,如果你有此类设备就可以启用,具体
请参考AX25和HAM HOWTO 文档。
isdn subsystem
如果你有ISDN硬件就应该启用该选项并安装合适的硬件驱动程
序,你应该还会需要启用Support synchronous PPP选项(参考PPP over
ISDN)。
old cd-rom drivers
这是针对一些特殊光盘驱动器程序的问题,如果你有IDE或SCSI的
CDROM控制卡,那么就不用启用该选项了。
character devices
LINUX支持很多特殊的字符设备,例如并口、串口控制卡、QIC02磁
带驱动器以及特定界面的鼠标,此外对于游戏杆和影象摄取和麦
克等也在这里面,依据你自己的情况选者吧。
filesystems
这是一系列内核所支持的各文件系统的问题,对ext2 /proc文件系统
是一定应该支持的,有光驱还应该支持ISO9660(或模块支持),
有WINDOWS或DOS分区并且想在LINUX下访问他们也可以进行支
持。
console drivers
你至少应该支持VGA text console,否则你无法从控制台使用LINUX。
sound card support
在这里回答Y会出现很多关于声卡的问题,根据你自己的情况来配
置。
kernel profiling support(v1.3)
这个选项可以开启内核做效率统计的功能,并且会提供其他在为
系统侦错时有用的信息。这些功能会需要付出一些代价并造成系
统执行得较为缓慢,除非你正在研究内核的某个问题,否则你应
该回答N。
kernel hacking
如果你正打算深入研究自己系统上运行的LINUX如何运作,这里有
很多选项,但一般没有必要的话可以全部关掉。
作者对文章的正确性不做任何保证,如果你发现本文的不足或错
误,请更正并重新发布。
欢迎转载并进行修正,转载及少量修正请注明原作者,如果对本
文进行了任何修改,请寄一份给原作者,谢谢。
这个是我大学的时候利用寒假的时间翻译的,记得当时还特意让我妈买了一个电取暖器,窝在家里很长时间才弄完的,可惜时间太长,原件我这里都没有了,现在也没有找到可以下载全部内容的地方了。贴个链接在这里做个纪念吧,毕竟是我最开始为开源做出的一点贡献。
现在的公司招人一般都要求各种工作经验,有的对于比较低级的职位也要求精通一大堆东西,而这些对于还未真正工作过的人而言简直就是强人所难,而且似乎还有一个先有鸡还是先有蛋的问题。
如果以前没有工作,那么哪儿来的工作经验呢?但是如果没有工作经验你就得不到工作。
如果以前没有鸡,那么哪儿来的蛋?如果没有蛋,鸡是哪儿来的?
12号晚上有流星雨,但是要到灯光污染比较小的地方才好看,自从大学的那次寒冷的夜晚后还没有再看过,这次要不要看呢?
2005英仙座流星雨
/proc/sys/net/ipv4/* Variables:
ip_forward - BOOLEAN
0 - disabled (default)
not 0 - enabled
Forward Packets between interfaces.
This variable is special, its change resets all configuration
parameters to their default state (RFC1122 for hosts, RFC1812
for routers)
ip_default_ttl - INTEGER
default 64
ip_no_pmtu_disc - BOOLEAN
Disable Path MTU Discovery.
default FALSE
IP Fragmentation:
ipfrag_high_thresh - INTEGER
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_low_thresh - INTEGER
See ipfrag_high_thresh
ipfrag_time - INTEGER
Time in seconds to keep an IP fragment in memory.
ipfrag_secret_interval - INTEGER
Regeneration interval (in seconds) of the hash secret (or lifetime
for the hash secret) for IP fragments.
Default: 600
INET peer storage:
inet_peer_threshold - INTEGER
The approximate size of the storage. Starting from this threshold
entries will be thrown aggressively. This threshold also determines
entries' time-to-live and time intervals between garbage collection
passes. More entries, less time-to-live, less GC interval.
inet_peer_minttl - INTEGER
Minimum time-to-live of entries. Should be enough to cover fragment
time-to-live on the reassembling side. This minimum time-to-live is
guaranteed if the pool size is less than inet_peer_threshold.
Measured in jiffies(1).
inet_peer_maxttl - INTEGER
Maximum time-to-live of entries. Unused entries will expire after
this period of time if there is no memory pressure on the pool (i.e.
when the number of entries in the pool is very small).
Measured in jiffies(1).
inet_peer_gc_mintime - INTEGER
Minimum interval between garbage collection passes. This interval is
in effect under high memory pressure on the pool.
Measured in jiffies(1).
inet_peer_gc_maxtime - INTEGER
Minimum interval between garbage collection passes. This interval is
in effect under low (or absent) memory pressure on the pool.
Measured in jiffies(1).
TCP variables:
tcp_syn_retries - INTEGER
Number of times initial SYNs for an active TCP connection attempt
will be retransmitted. Should not be higher than 255. Default value
is 5, which corresponds to ~180seconds.
tcp_synack_retries - INTEGER
Number of times SYNACKs for a passive TCP connection attempt will
be retransmitted. Should not be higher than 255. Default value
is 5, which corresponds to ~180seconds.
tcp_keepalive_time - INTEGER
How often TCP sends out keepalive messages when keepalive is enabled.
Default: 2hours.
tcp_keepalive_probes - INTEGER
How many keepalive probes TCP sends out, until it decides that the
connection is broken. Default value: 9.
tcp_keepalive_intvl - INTEGER
How frequently the probes are send out. Multiplied by
tcp_keepalive_probes it is time to kill not responding connection,
after probes started. Default value: 75sec i.e. connection
will be aborted after ~11 minutes of retries.
tcp_retries1 - INTEGER
How many times to retry before deciding that something is wrong
and it is necessary to report this suspicion to network layer.
Minimal RFC value is 3, it is default, which corresponds
to ~3sec-8min depending on RTO.
tcp_retries2 - INTEGER
How may times to retry before killing alive TCP connection.
RFC1122 says that the limit should be longer than 100 sec.
It is too small number. Default value 15 corresponds to ~13-30min
depending on RTO.
tcp_orphan_retries - INTEGER
How may times to retry before killing TCP connection, closed
by our side. Default value 7 corresponds to ~50sec-16min
depending on RTO. If you machine is loaded WEB server,
you should think about lowering this value, such sockets
may consume significant resources. Cf. tcp_max_orphans.
tcp_fin_timeout - INTEGER
Time to hold socket in state FIN-WAIT-2, if it was closed
by our side. Peer can be broken and never close its side,
or even died unexpectedly. Default value is 60sec.
Usual value used in 2.2 was 180 seconds, you may restore
it, but remember that if your machine is even underloaded WEB server,
you risk to overflow memory with kilotons of dead sockets,
FIN-WAIT-2 sockets are less dangerous than FIN-WAIT-1,
because they eat maximum 1.5K of memory, but they tend
to live longer. Cf. tcp_max_orphans.
tcp_max_tw_buckets - INTEGER
Maximal number of timewait sockets held by system simultaneously.
If this number is exceeded time-wait socket is immediately destroyed
and warning is printed. This limit exists only to prevent
simple DoS attacks, you _must_ not lower the limit artificially,
but rather increase it (probably, after increasing installed memory),
if network conditions require more than default value.
tcp_tw_recycle - BOOLEAN
Enable fast recycling TIME-WAIT sockets. Default value is 0.
It should not be changed without advice/request of technical
experts.
tcp_tw_reuse - BOOLEAN
Allow to reuse TIME-WAIT sockets for new connections when it is
safe from protocol viewpoint. Default value is 0.
It should not be changed without advice/request of technical
experts.
tcp_max_orphans - INTEGER
Maximal number of TCP sockets not attached to any user file handle,
held by system. If this number is exceeded orphaned connections are
reset immediately and warning is printed. This limit exists
only to prevent simple DoS attacks, you _must_ not rely on this
or lower the limit artificially, but rather increase it
(probably, after increasing installed memory),
if network conditions require more than default value,
and tune network services to linger and kill such states
more aggressively. Let me to remind again: each orphan eats
up to ~64K of unswappable memory.
tcp_abort_on_overflow - BOOLEAN
If listening service is too slow to accept new connections,
reset them. Default state is FALSE. It means that if overflow
occurred due to a burst, connection will recover. Enable this
option _only_ if you are really sure that listening daemon
cannot be tuned to accept connections faster. Enabling this
option can harm clients of your server.
tcp_syncookies - BOOLEAN
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 prevent against the common 'syn flood attack'
Default: FALSE
Note, that syncookies is fallback facility.
It MUST NOT be used to help highly loaded servers to stand
against legal connection rate. If you see synflood warnings
in your logs, but investigation shows that they occur
because of overload with legal connections, you should tune
another parameters until this warning disappear.
See: tcp_max_syn_backlog, tcp_synack_retries, tcp_abort_on_overflow.
syncookies seriously violate TCP protocol, do not allow
to use TCP extensions, can result in serious degradation
of some services (f.e. SMTP relaying), visible not by you,
but your clients and relays, contacting you. While you see
synflood warnings in logs not being really flooded, your server
is seriously misconfigured.
tcp_stdurg - BOOLEAN
Use the Host requirements interpretation of the TCP urg pointer field.
Most hosts use the older BSD interpretation, so if you turn this on
Linux might not communicate correctly with them.
Default: FALSE
tcp_max_syn_backlog - INTEGER
Maximal number of remembered connection requests, which are
still did not receive an acknowledgment from connecting client.
Default value is 1024 for systems with more than 128Mb of memory,
and 128 for low memory machines. If server suffers of overload,
try to increase this number.
tcp_window_scaling - BOOLEAN
Enable window scaling as defined in RFC1323.
tcp_timestamps - BOOLEAN
Enable timestamps as defined in RFC1323.
tcp_sack - BOOLEAN
Enable select acknowledgments (SACKS).
tcp_fack - BOOLEAN
Enable FACK congestion avoidance and fast retransmission.
The value is not used, if tcp_sack is not enabled.
tcp_dsack - BOOLEAN
Allows TCP to send "duplicate" SACKs.
tcp_ecn - BOOLEAN
Enable Explicit Congestion Notification in TCP.
tcp_reordering - INTEGER
Maximal reordering of packets in a TCP stream.
Default: 3
tcp_retrans_collapse - BOOLEAN
Bug-to-bug compatibility with some broken printers.
On retransmit try to send bigger packets to work around bugs in
certain TCP stacks.
tcp_wmem - vector of 3 INTEGERs: min, default, max
min: Amount of memory reserved for send buffers for TCP socket.
Each TCP socket has rights to use it due to fact of its birth.
Default: 4K
default: Amount of memory allowed for send buffers for TCP socket
by default. This value overrides net.core.wmem_default used
by other protocols, it is usually lower than net.core.wmem_default.
Default: 16K
max: Maximal amount of memory allowed for automatically selected
send buffers for TCP socket. This value does not override
net.core.wmem_max, "static" selection via SO_SNDBUF does not use this.
Default: 128K
tcp_rmem - vector of 3 INTEGERs: min, default, max
min: Minimal size of receive buffer used by TCP sockets.
It is guaranteed to each TCP socket, even under moderate memory
pressure.
Default: 8K
default: default size of receive buffer used by TCP sockets.
This value overrides net.core.rmem_default used by other protocols.
Default: 87380 bytes. This value results in window of 65535 with
default setting of tcp_adv_win_scale and tcp_app_win:0 and a bit
less for default tcp_app_win. See below about these variables.
max: maximal size of receive buffer allowed for automatically
selected receiver buffers for TCP socket. This value does not override
net.core.rmem_max, "static" selection via SO_RCVBUF does not use this.
Default: 87380*2 bytes.
tcp_mem - vector of 3 INTEGERs: min, pressure, max
low: below this number of pages TCP is not bothered about its
memory appetite.
pressure: when amount of memory allocated by TCP exceeds this number
of pages, TCP moderates its memory consumption and enters memory
pressure mode, which is exited when memory consumption falls
under "low".
high: number of pages allowed for queueing by all TCP sockets.
Defaults are calculated at boot time from amount of available
memory.
tcp_app_win - INTEGER
Reserve max(window/2^tcp_app_win, mss) of window for application
buffer. Value 0 is special, it means that nothing is reserved.
Default: 31
tcp_adv_win_scale - INTEGER
Count buffering overhead as bytes/2^tcp_adv_win_scale
(if tcp_adv_win_scale > 0) or bytes-bytes/2^(-tcp_adv_win_scale),
if it is <= 0.
Default: 2
tcp_rfc1337 - BOOLEAN
If set, the TCP stack behaves conforming to RFC1337. If unset,
we are not conforming to RFC, but prevent TCP TIME_WAIT
assassination.
Default: 0
tcp_low_latency - BOOLEAN
If set, the TCP stack makes decisions that prefer lower
latency as opposed to higher throughput. By default, this
option is not set meaning that higher throughput is preferred.
An example of an application where this default should be
changed would be a Beowulf compute cluster.
Default: 0
ip_local_port_range - 2 INTEGERS
Defines the local port range that is used by TCP and UDP to
choose the local port. The first number is the first, the
second the last local port number. Default value depends on
amount of memory available on the system:
> 128Mb 32768-61000
< 128Mb 1024-4999 or even less.
This number defines number of active connections, which this
system can issue simultaneously to systems not supporting
TCP extensions (timestamps). With tcp_tw_recycle enabled
(i.e. by default) range 1024-4999 is enough to issue up to
2000 connections per second to systems supporting timestamps.
ip_nonlocal_bind - BOOLEAN
If set, allows processes to bind() to non-local IP addresses,
which can be quite useful - but may break some applications.
Default: 0
ip_dynaddr - BOOLEAN
If set non-zero, enables support for dynamic addresses.
If set to a non-zero value larger than 1, a kernel log
message will be printed when dynamic address rewriting
occurs.
Default: 0
icmp_echo_ignore_all - BOOLEAN
icmp_echo_ignore_broadcasts - BOOLEAN
If either is set to true, then the kernel will ignore either all
ICMP ECHO requests sent to it or just those to broadcast/multicast
addresses, respectively.
icmp_ratelimit - INTEGER
Limit the maximal rates for sending ICMP packets whose type matches
icmp_ratemask (see below) to specific targets.
0 to disable any limiting, otherwise the maximal rate in jiffies(1)
Default: 100
icmp_ratemask - INTEGER
Mask made of ICMP types for which rates are being limited.
Significant bits: IHGFEDCBA9876543210
Default mask: 0000001100000011000 (6168)
Bit definitions (see include/linux/icmp.h):
0 Echo Reply
3 Destination Unreachable *
4 Source Quench *
5 Redirect
8 Echo Request
B Time Exceeded *
C Parameter Problem *
D Timestamp Request
E Timestamp Reply
F Info Request
G Info Reply
H Address Mask Request
I Address Mask Reply
* These are rate limited by default (see default mask above)
icmp_ignore_bogus_error_responses - BOOLEAN
Some routers violate RFC1122 by sending bogus responses to broadcast
frames. Such violations are normally logged via a kernel warning.
If this is set to TRUE, the kernel will not give such warnings, which
will avoid log file clutter.
Default: FALSE
igmp_max_memberships - INTEGER
Change the maximum number of multicast groups we can subscribe to.
Default: 20
conf/interface/* changes special settings per interface (where "interface" is
the name of your network interface)
conf/all/* is special, changes the settings for all interfaces
log_martians - BOOLEAN
Log packets with impossible addresses to kernel log.
log_martians for the interface will be enabled if at least one of
conf/{all,interface}/log_martians is set to TRUE,
it will be disabled otherwise
accept_redirects - BOOLEAN
Accept ICMP redirect messages.
accept_redirects for the interface will be enabled if:
- both conf/{all,interface}/accept_redirects are TRUE in the case forwarding
for the interface is enabled
or
- at least one of conf/{all,interface}/accept_redirects is TRUE in the case
forwarding for the interface is disabled
accept_redirects for the interface will be disabled otherwise
default TRUE (host)
FALSE (router)
forwarding - BOOLEAN
Enable IP forwarding on this interface.
mc_forwarding - BOOLEAN
Do multicast routing. The kernel needs to be compiled with CONFIG_MROUTE
and a multicast routing daemon is required.
conf/all/mc_forwarding must also be set to TRUE to enable multicast routing
for the interface
medium_id - INTEGER
Integer value used to differentiate the devices by the medium they
are attached to. Two devices can have different id values when
the broadcast packets are received only on one of them.
The default value 0 means that the device is the only interface
to its medium, value of -1 means that medium is not known.
Currently, it is used to change the proxy_arp behavior:
the proxy_arp feature is enabled for packets forwarded between
two devices attached to different media.
proxy_arp - BOOLEAN
Do proxy arp.
proxy_arp for the interface will be enabled if at least one of
conf/{all,interface}/proxy_arp is set to TRUE,
it will be disabled otherwise
shared_media - BOOLEAN
Send(router) or accept(host) RFC1620 shared media redirects.
Overrides ip_secure_redirects.
shared_media for the interface will be enabled if at least one of
conf/{all,interface}/shared_media is set to TRUE,
it will be disabled otherwise
default TRUE
secure_redirects - BOOLEAN
Accept ICMP redirect messages only for gateways,
listed in default gateway list.
secure_redirects for the interface will be enabled if at least one of
conf/{all,interface}/secure_redirects is set to TRUE,
it will be disabled otherwise
default TRUE
send_redirects - BOOLEAN
Send redirects, if router.
send_redirects for the interface will be enabled if at least one of
conf/{all,interface}/send_redirects is set to TRUE,
it will be disabled otherwise
Default: TRUE
bootp_relay - BOOLEAN
Accept packets with source address 0.b.c.d destined
not to this host as local ones. It is supposed, that
BOOTP relay daemon will catch and forward such packets.
conf/all/bootp_relay must also be set to TRUE to enable BOOTP relay
for the interface
default FALSE
Not Implemented Yet.
accept_source_route - BOOLEAN
Accept packets with SRR option.
conf/all/accept_source_route must also be set to TRUE to accept packets
with SRR option on the interface
default TRUE (router)
FALSE (host)
rp_filter - BOOLEAN
1 - do source validation by reversed path, as specified in RFC1812
Recommended option for single homed hosts and stub network
routers. Could cause troubles for complicated (not loop free)
networks running a slow unreliable protocol (sort of RIP),
or using static routes.
0 - No source validation.
conf/all/rp_filter must also be set to TRUE to do source validation
on the interface
Default value is 0. Note that some distributions enable it
in startup scripts.
arp_filter - BOOLEAN
1 - Allows you to have multiple network interfaces on the same
subnet, and have the ARPs for each interface be answered
based on whether or not the kernel would route a packet from
the ARP'd IP out that interface (therefore you must use source
based routing for this to work). In other words it allows control
of which cards (usually 1) will respond to an arp request.
0 - (default) The kernel can respond to arp requests with addresses
from other interfaces. This may seem wrong but it usually makes
sense, because it increases the chance of successful communication.
IP addresses are owned by the complete host on Linux, not by
particular interfaces. Only for more complex setups like load-
balancing, does this behaviour cause problems.
arp_filter for the interface will be enabled if at least one of
conf/{all,interface}/arp_filter is set to TRUE,
it will be disabled otherwise
tag - INTEGER
Allows you to write a number, which can be used as required.
Default value is 0.
(1) Jiffie: internal timeunit for the kernel. On the i386 1/100s, on the
Alpha 1/1024s. See the HZ define in /usr/include/asm/param.h for the exact
value on your system.
Alexey Kuznetsov.
kuznet-AT-ms2.inr.ac-DOT-ru
Updated by:
Andi Kleen
ak-AT-muc-DOT-de
Nicolas Delon
delon.nicolas-AT-wanadoo-DOT-fr
/proc/sys/net/ipv6/* Variables:
IPv6 has no global variables such as tcp_*. tcp_* settings under ipv4/ also
apply to IPv6 [XXX?].
bindv6only - BOOLEAN
Default value for IPV6_V6ONLY socket option,
which restricts use of the IPv6 socket to IPv6 communication
only.
TRUE: disable IPv4-mapped address feature
FALSE: enable IPv4-mapped address feature
Default: FALSE (as specified in RFC2553bis)
IPv6 Fragmentation:
ip6frag_high_thresh - INTEGER
Maximum memory used to reassemble IPv6 fragments. When
ip6frag_high_thresh bytes of memory is allocated for this purpose,
the fragment handler will toss packets until ip6frag_low_thresh
is reached.
ip6frag_low_thresh - INTEGER
See ip6frag_high_thresh
ip6frag_time - INTEGER
Time in seconds to keep an IPv6 fragment in memory.
ip6frag_secret_interval - INTEGER
Regeneration interval (in seconds) of the hash secret (or lifetime
for the hash secret) for IPv6 fragments.
Default: 600
conf/default/*:
Change the interface-specific default settings.
conf/all/*:
Change all the interface-specific settings.
[XXX: Other special features than forwarding?]
conf/all/forwarding - BOOLEAN
Enable global IPv6 forwarding between all interfaces.
IPv4 and IPv6 work differently here; e.g. netfilter must be used
to control which interfaces may forward packets and which not.
This also sets all interfaces' Host/Router setting
'forwarding' to the specified value. See below for details.
This referred to as global forwarding.
conf/interface/*:
Change special settings per interface.
The functional behaviour for certain settings is different
depending on whether local forwarding is enabled or not.
accept_ra - BOOLEAN
Accept Router Advertisements; autoconfigure using them.
Functional default: enabled if local forwarding is disabled.
disabled if local forwarding is enabled.
accept_redirects - BOOLEAN
Accept Redirects.
Functional default: enabled if local forwarding is disabled.
disabled if local forwarding is enabled.
autoconf - BOOLEAN
Configure link-local addresses using L2 hardware addresses.
Default: TRUE
dad_transmits - INTEGER
The amount of Duplicate Address Detection probes to send.
Default: 1
forwarding - BOOLEAN
Configure interface-specific Host/Router behaviour.
Note: It is recommended to have the same setting on all
interfaces; mixed router/host scenarios are rather uncommon.
FALSE:
By default, Host behaviour is assumed. This means:
1. IsRouter flag is not set in Neighbour Advertisements.
2. Router Solicitations are being sent when necessary.
3. If accept_ra is TRUE (default), accept Router
Advertisements (and do autoconfiguration).
4. If accept_redirects is TRUE (default), accept Redirects.
TRUE:
If local forwarding is enabled, Router behaviour is assumed.
This means exactly the reverse from the above:
1. IsRouter flag is set in Neighbour Advertisements.
2. Router Solicitations are not sent.
3. Router Advertisements are ignored.
4. Redirects are ignored.
Default: FALSE if global forwarding is disabled (default),
otherwise TRUE.
hop_limit - INTEGER
Default Hop Limit to set.
Default: 64
mtu - INTEGER
Default Maximum Transfer Unit
Default: 1280 (IPv6 required minimum)
router_solicitation_delay - INTEGER
Number of seconds to wait after interface is brought up
before sending Router Solicitations.
Default: 1
router_solicitation_interval - INTEGER
Number of seconds to wait between Router Solicitations.
Default: 4
router_solicitations - INTEGER
Number of Router Solicitations to send until assuming no
routers are present.
Default: 3
use_tempaddr - INTEGER
Preference for Privacy Extensions (RFC3041).
<= 0 : disable Privacy Extensions
== 1 : enable Privacy Extensions, but prefer public
addresses over temporary addresses.
> 1 : enable Privacy Extensions and prefer temporary
addresses over public addresses.
Default: 0 (for most devices)
-1 (for point-to-point devices and loopback devices)
temp_valid_lft - INTEGER
valid lifetime (in seconds) for temporary addresses.
Default: 604800 (7 days)
temp_prefered_lft - INTEGER
Preferred lifetime (in seconds) for temorary addresses.
Default: 86400 (1 day)
max_desync_factor - INTEGER
Maximum value for DESYNC_FACTOR, which is a random value
that ensures that clients don't synchronize with each
other and generage new addresses at exactly the same time.
value is in seconds.
Default: 600
regen_max_retry - INTEGER
Number of attempts before give up attempting to generate
valid temporary addresses.
Default: 5
icmp/*:
ratelimit - INTEGER
Limit the maximal rates for sending ICMPv6 packets.
0 to disable any limiting, otherwise the maximal rate in jiffies(1)
Default: 100
IPv6 Update by:
Pekka Savola <pekkas-AT-netcore-DOT-fi>
YOSHIFUJI Hideaki / USAGI Project <yoshfuji@linux-ipv6.org>
$Id: ip-sysctl.txt,v 1.20 2001/12/13 09:00:18 davem Exp $
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