1MEMCACHED(1) General Commands Manual MEMCACHED(1)
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6 memcached - high-performance memory object caching system
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9 memcached [options]
10
12 This manual page documents briefly the memcached memory object caching
13 daemon.
14 memcached is a flexible memory object caching daemon designed to alle‐
16 viate database load in dynamic web applications by storing objects in
17 memory. It's based on libevent to scale to any size needed, and is
18 specifically optimized to avoid swapping and always use non-blocking
19 I/O.
20
22 These programs follow the usual GNU command line syntax. A summary of
23 options is included below.
24 -s, --unix-socket=<file>
26 Unix socket path to listen on (disables network support).
27 -A, --enable-shutdown
29 Enable ascii "shutdown" command.
30 -a, --unix-mask=<perms>
32 Permissions (in octal format) for Unix socket created with -s
33 option.
34 -l, --listen=<addr>
36 Listen on <addr>; default to INADDR_ANY. <addr> may be specified
37 as host:port. If you don't specify a port number, the value you
38 specified with -p or -U is used. You may specify multiple
39 addresses separated by comma or by using -l multiple times. This
40 is an important option to consider as there is no other way to
41 secure the installation. Binding to an internal or firewalled
42 network interface is suggested.
43 -d, --daemon
45 Run memcached as a daemon.
46 -u, --user=<username>
48 Assume the identity of <username> (only when run as root).
49 -m, --memory-limit=<num>
51 Use <num> MB memory max to use for object storage; the default
52 is 64 megabytes.
53 -c, --conn-limit=<num>
55 Use <num> max simultaneous connections; the default is 1024.
56 -R, --max-reqs-per-event=<num>
58 This option seeks to prevent client starvation by setting a
59 limit to the number of sequential requests the server will
60 process from an individual client connection. Once a connection
61 has exceeded this value, the server will attempt to process I/O
62 on other connections before handling any further request from
63 this connection. The default value for this option is 20.
64 -k, --lock-memory
66 Lock down all paged memory. This is a somewhat dangerous option
67 with large caches, so consult the README and memcached homepage
68 for configuration suggestions.
69 -p, --port=<num>
71 Listen on TCP port <num>, the default is port 11211. 0 means
72 off.
73 -U, --udp-port=<num>
75 Listen on UDP port <num>, the default is port 0, which is off.
76 -M, --disable-evictions
78 Disable automatic removal of items from the cache when out of
79 memory. Additions will not be possible until adequate space is
80 freed up.
81 -r, --enable-coredumps
83 Raise the core file size limit to the maximum allowable.
84 -f, --slab-growth-factor=<factor>
86 Use <factor> as the multiplier for computing the sizes of memory
87 chunks that items are stored in. A lower value may result in
88 less wasted memory depending on the total amount of memory
89 available and the distribution of item sizes. The default is
90 1.25.
91 -n, --slab-min-size=<size>
93 Allocate a minimum of <size> bytes for the item key, value, and
94 flags. The default is 48. If you have a lot of small keys and
95 values, you can get a significant memory efficiency gain with a
96 lower value. If you use a high chunk growth factor (-f option),
97 on the other hand, you may want to increase the size to allow a
98 bigger percentage of your items to fit in the most densely
99 packed (smallest) chunks.
100 -C, --disable-cas
102 Disable the use of CAS (and reduce the per-item size by 8
103 bytes).
104 -h, --help
106 Show the version of memcached and a summary of options.
107 -v, --verbose
109 Be verbose during the event loop; print out errors and warnings.
110 -vv Be even more verbose; same as -v but also print client commands
112 and responses.
113 -vvv Be extremely verbose; same of the above and also print internal
115 state transitions.
116 -i, --license
118 Print memcached and libevent licenses.
119 -P, --pidfile=<filename>
121 Print pidfile to <filename>, only used under -d option.
122 -t, --threads=<threads>
124 Number of threads to use to process incoming requests. This
125 option is only meaningful if memcached was compiled with thread
126 support enabled. It is typically not useful to set this higher
127 than the number of CPU cores on the memcached server. Setting a
128 high number (64 or more) of worker threads is not recommended.
129 The default is 4.
130 -D <char>
132 Use <char> as the delimiter between key prefixes and IDs. This
133 is used for per-prefix stats reporting. The default is ":"
134 (colon). If this option is specified, stats collection is turned
135 on automatically; if not, then it may be turned on by sending
136 the "stats detail on" command to the server.
137 -L, --enable-largepages
139 Try to use large memory pages (if available). Increasing the
140 memory page size could reduce the number of TLB misses and
141 improve the performance. In order to get large pages from the
142 OS, memcached will allocate the total item-cache in one large
143 chunk. Only available if supported on your OS.
144 -b, --listen-backlog=<num>
146 Set the backlog queue limit to <num> connections. The default is
147 1024.
148 -B, --protocol=<proto>
150 Specify the binding protocol to use. By default, the server
151 will autonegotiate client connections. By using this option,
152 you can specify the protocol clients must speak. Possible
153 options are "auto" (the default, autonegotiation behavior),
154 "ascii" and "binary".
155 -I, --max-item-size=<size>
157 Override the default size of each slab page. The default size is
158 1mb. Default value for this parameter is 1m, minimum is 1k, max
159 is 128m. Adjusting this value changes the item size limit.
160 -S, --enable-sasl
162 Turn on SASL authentication. This option is only meaningful if
163 memcached was compiled with SASL support enabled.
164 -F, --disable-flush-all
166 Disables the "flush_all" command. The cmd_flush counter will
167 increment, but clients will receive an error message and the
168 flush will not occur.
169 -X, --disable-dumping
171 Disables the "stats cachedump" and "lru_crawler metadump" com‐
172 mands.
173 -o, --extended=<options>
175 Comma separated list of extended or experimental options. See -h
176 or wiki for up to date list.
177 -V, --version
179 print version and exit
180
182 The memcached daemon is copyright Danga Interactive and is distributed
183 under the BSD license. Note that daemon clients are licensed sepa‐
184 rately.
185
187 The README file that comes with memcached
188 https://www.memcached.org
189
191 The memcached daemon was written by Anatoly Vorobey <mellon@pobox.com>
192 and Brad Fitzpatrick <brad@danga.com> and the rest of the crew of Danga
193 Interactive https://www.danga.com
194 April 11, 2005 MEMCACHED(1)