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MEMCACHED(1)		    General Commands Manual		  MEMCACHED(1)

       memcached - high-performance memory object caching system

       memcached [options]

       This  manual page documents briefly the memcached memory	object caching

       memcached is a flexible memory object caching daemon designed to	 alle-
       viate  database	load in	dynamic	web applications by storing objects in
       memory.	It's based on libevent to scale	to any	size  needed,  and  is
       specifically  optimized	to  avoid swapping and always use non-blocking

       These programs follow the usual GNU command line	syntax.	A  summary  of
       options is included below.

       -s <file>
	      Unix socket path to listen on (disables network support).

       -A     Enable ascii "shutdown" command.

       -a <perms>
	      Permissions  (in	octal  format) for Unix	socket created with -s

       -l <addr>
	      Listen on	<addr>;	default	to INADDR_ANY. <addr> may be specified
	      as host:port.  If	you don't specify a port number, the value you
	      specified	with -p	or -U is used. You may	specify	 multiple  ad-
	      dresses  separated  by comma or by using -l multiple times. This
	      is an important option to	consider as there is no	other  way  to
	      secure  the  installation.  Binding to an	internal or firewalled
	      network interface	is suggested.

       -d     Run memcached as a daemon.

       -u <username>
	      Assume the identity of <username>	(only when run as root).

       -m <num>
	      Use <num>	MB memory max to use for object	storage;  the  default
	      is 64 megabytes.

       -c <num>
	      Use <num>	max simultaneous connections; the default is 1024.

       -R <num>
	      This  option  seeks  to  prevent	client starvation by setting a
	      limit to the number  of  sequential  requests  the  server  will
	      process  from an individual client connection. Once a connection
	      has exceeded this	value, the server will attempt to process  I/O
	      on  other	 connections  before handling any further request from
	      this connection. The default value for this option is 20.

       -k     Lock down	all paged memory. This is a somewhat dangerous	option
	      with  large caches, so consult the README	and memcached homepage
	      for configuration	suggestions.

       -p <num>
	      Listen on	TCP port <num>,	the default is port 11211.

       -U <num>
	      Listen on	UDP port <num>,	the default is port 11211, 0 is	off.

       -M     Disable automatic	removal	of items from the cache	 when  out  of
	      memory.	Additions will not be possible until adequate space is
	      freed up.

       -r     Raise the	core file size limit to	the maximum allowable.

       -f <factor>
	      Use <factor> as the multiplier for computing the sizes of	memory
	      chunks  that  items  are	stored in. A lower value may result in
	      less wasted memory depending  on	the  total  amount  of	memory
	      available	 and  the  distribution	of item	sizes.	The default is

       -n <size>
	      Allocate a minimum of <size> bytes for the item key, value,  and
	      flags.  The  default  is 48. If you have a lot of	small keys and
	      values, you can get a significant	memory efficiency gain with  a
	      lower  value. If you use a high chunk growth factor (-f option),
	      on the other hand, you may want to increase the size to allow  a
	      bigger  percentage  of  your  items  to  fit in the most densely
	      packed (smallest)	chunks.

       -C     Disable the use of CAS  (and  reduce  the	 per-item  size	 by  8

       -h     Show the version of memcached and	a summary of options.

       -v     Be verbose during	the event loop;	print out errors and warnings.

       -vv    Be  even more verbose; same as -v	but also print client commands
	      and responses.

       -vvv   Be extremely verbose; same of the	above and also print  internal
	      state transitions.

       -i     Print memcached and libevent licenses.

       -P <filename>
	      Print pidfile to <filename>, only	used under -d option.

       -t <threads>
	      Number  of threads to use	to process incoming requests. This op-
	      tion is only meaningful if memcached was	compiled  with	thread
	      support  enabled.	 It is typically not useful to set this	higher
	      than the number of CPU cores on the memcached server. Setting  a
	      high  number  (64	or more) of worker threads is not recommended.
	      The default is 4.

       -D <char>
	      Use <char> as the	delimiter between key prefixes and  IDs.  This
	      is  used	for  per-prefix	 stats	reporting.  The	default	is ":"
	      (colon). If this option is specified, stats collection is	turned
	      on  automatically;  if  not, then	it may be turned on by sending
	      the "stats detail	on" command to the server.

       -L     Try to use large memory pages  (if  available).  Increasing  the
	      memory  page  size could reduce the number of TLB	misses and im-
	      prove the	performance. In	order to get large pages from the  OS,
	      memcached	will allocate the total	item-cache in one large	chunk.
	      Only available if	supported on your OS.

       -b <num>
	      Set the backlog queue limit to <num> connections.	The default is

       -B <proto>
	      Specify  the  binding  protocol  to use.	By default, the	server
	      will autonegotiate client	connections.  By  using	 this  option,
	      you  can	specify	the protocol clients must speak.  Possible op-
	      tions  are  "auto"  (the	default,  autonegotiation   behavior),
	      "ascii" and "binary".

       -I <size>
	      Override the default size	of each	slab page. The default size is
	      1mb. Default value for this parameter is 1m, minimum is 1k,  max
	      is 128m.	Adjusting this value changes the item size limit.  Be-
	      ware that	this also increases the	number of  slabs  (use	-v  to
	      view), and the overal memory usage of memcached.

       -S     Turn  on	SASL authentication. This option is only meaningful if
	      memcached	was compiled with SASL support enabled.

       -F     Disables the "flush_all" command.	The cmd_flush counter will in-
	      crement, but clients will	receive	an error message and the flush
	      will not occur.

       -X     Disables the "stats cachedump" and "lru_crawler  metadump"  com-

       -o <options>
	      Comma separated list of extended or experimental options.	See -h
	      or wiki for up to	date list.

       -V     print version and	exit

       The memcached daemon is copyright Danga Interactive and is  distributed
       under  the  BSD	license.  Note	that daemon clients are	licensed sepa-

       The README file that comes with memcached

       The memcached daemon was	written	by Anatoly Vorobey  <>
       and Brad	Fitzpatrick <> and the rest of the crew of Danga

				April 11, 2005			  MEMCACHED(1)


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