rrdcached - Data caching daemon for rrdtool
rrdcached [-a alloc_size] [-b base_dir [-B]] [-F] [-f timeout] [-G group]] [-g] [-j journal_dir] [-L] [-l address] [-m mode] [-O] [-P permissions] [-p pid_file] [-R] [-s group] [-t write_threads] [-U user]] [-w timeout] [-z delay]
rrdcached is a daemon that receives updates to existing RRD files, accumulates them and, if enough have been received or a defined time has passed, writes the updates to the RRD file. A flush command may be used to force writing of values to disk, so that graphing facilities and similar can work with up-to-date data.
The daemon was written with big setups in mind. Those setups usually run into IO related problems sooner or later for reasons that are beyond the scope of this document. Check the wiki at the RRDtool homepage for details. Also check "SECURITY CONSIDERATIONS" below before using this daemon! A detailed description of how the daemon operates can be found in the "HOW IT WORKS" section below.
Tells the daemon to bind to address and accept incoming TCP connections on that socket. If address begins with unix:, everything following that prefix is interpreted as the path to a UNIX domain socket. Otherwise the address or node name are resolved using getaddrinfo().
For network sockets, a port may be specified by using the form [address]:port. If the address is an IPv4 address or a fully qualified domain name (i. e. the address contains at least one dot (.)), the square brackets can be omitted, resulting in the (simpler) address:port pattern. The default port is 42217. If you specify a network socket, it is mandatory to read the "SECURITY CONSIDERATIONS" section.
The following formats are accepted. Please note that the address of the UNIX domain socket must start with a slash in the second case!
unix:</path/to/unix.sock>
/<path/to/unix.sock>
<hostname-or-ip>
[<hostname-or-ip>]:<port>
<hostname-or-ipv4>:<port>Given a port without a host (e.g. -l :42217) the daemon will listen on that port on all network interfaces. Use -L to avoid the need to explicitly provide the port if the default port is desired.
If no -l option is not specified the default address, unix:/tmp/rrdcached.sock, will be used. Multiple -l options may be provided.
Tells the daemon to bind to the default TCP port on all available interfaces. It is equivalent to -l '' without the confusion of the empty string parameter.
Set the group permissions of a UNIX domain socket. The option accepts either a numeric group id or group name. That group will then have both read and write permissions (the socket will have file permissions 0760) for the socket and, therefore, is able to send commands to the daemon. This may be useful in cases where you cannot easily run all RRD processes with the same user privileges (e.g. graph generating CGI scripts that typically run in the permission context of the web server).
This option affects the following UNIX socket addresses (the following -l options) or the default socket (if no -l options have been specified), i.e., you may specify different settings for different sockets.
The default is not to change ownership or permissions of the socket and, thus, use the system default.
Set the file permissions of a UNIX domain socket. The option accepts an octal number representing the bit pattern for the mode (see chmod(1) for details).
Please note that not all systems honor this setting. On Linux, read/write permissions are required to connect to a UNIX socket. However, many BSD-derived systems ignore permissions for UNIX sockets. See unix(7) for details.
This option affects the following UNIX socket addresses (the following -l options) or the default socket (if no -l options have been specified), i.e., you may specify different settings for different sockets.
The default is not to change ownership or permissions of the socket and, thus, use the system default.
Specifies the commands accepted via both a network and a UNIX socket. This allows administrators of RRDCacheD to control the actions accepted from various sources.
The arguments given to the -P option is a comma separated list of commands. For example, to allow the FLUSH and PENDING commands one could specify:
rrdcached -P FLUSH,PENDING $MORE_ARGUMENTSThe -P option affects the following socket addresses (the following -l options) or the default socket (if no -l options have been specified). In the following example, only the IPv4 network socket (address 10.0.0.1) will be restricted to the FLUSH and PENDING commands:
rrdcached -l unix:/some/path -P FLUSH,PENDING -l 10.0.0.1A complete list of available commands can be found in the section "Valid Commands"