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
       alleviate 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.

       -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.

       -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
              option 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. 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
              improve 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
              options are "auto" (the default, autonegotiation behavior),
              "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.

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

       -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

       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)