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

       -l <ip_addr>
              Listen on <ip_addr>; default to INADDR_ANY. 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.

       -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.

       -I     Override the size of each slab page in bytes. In mundane  words,
              it  adjusts  the  maximum  item size that memcached will accept.
              You can use the suffixes K and M to specify the size as well, so
              use  2000000  or  2000K or 2M if you want a maximum size of 2 MB
              per object.  It is not recommended to raise this limit  above  1
              MB due just to performance reasons.  The default value is 1 MB.

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

       -t <threads>
              Number  of  threads  to use to process incoming requests.  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.
              "ascii" and "binary".

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

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

       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

                               October 16, 2009                   MEMCACHED(1)
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