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POSTMASTER !!!POSTMASTER NAME SYNOPSIS DESCRIPTION NOTES USAGE ---- !!NAME postmaster - PostgreSQL multiuser database server !!SYNOPSIS __postmaster__ [[ __-A 0__ | __1__ ] [[ __-B__ ''nbuffers'' ] [[ __-c__ ''name''__=__''value'' ] [[ __-d__ ''debug-level'' ] [[ __-D__ ''datadir'' ] [[ __-F__ ] [[ __-h__ ''hostname'' ] [[ __-i__ ] [[ __-k__ ''directory'' ] [[ __-l__ ] [[ __-N__ ''max-connections'' ] [[ __-o__ ''extra-options'' ] [[ __-p__ ''port'' ] [[ __-S__ ] [[ __--__''name''__=__''value'' ] [[ __-n__ | __-s__ ] !!DESCRIPTION __postmaster__ is the PostgreSQL multiuser database server. In order for a client application to access a database it connects (over a network or locally) to a running __postmaster__. The __postmaster__ then starts a separate server process (``postgres(1)'') to handle the connection. The __postmaster__ also manages the communication among server processes. By default the __postmaster__ starts in the foreground and prints log messages to the standard output. In practical applications the __postmaster__ should be started as a background process, perhaps at boot time. One __postmaster__ always manages the data from exactly one database cluster. A database cluster is a collection of databases that is stored at a common file system location. When the postmaster starts it needs to know the location of the database cluster files (``data area''). This is done with the __-D__ invocation option or the __PGDATA__ environment variable; there is no default. More than one postmaster process can run on a system at one time, as long as they use different data areas and different communication ports (see below). A data area is created with initdb(1). __OPTIONS__ __postmaster__ accepts the following command line arguments. For a detailed discussion of the options consult the ''Administrator's Guide''. You can also save typing most of these options by setting up a configuration file. __-A 0|1__ Enables run-time assert checks, which is a debugging aid to detect programming mistakes. This is only available if it was enabled during compilation. If so, the default is on. __-B__ ''nbuffers'' Sets the number of shared buffers for use by the server processes. This value defaults to 64 buffers, where each buffer is 8 kB. __-c__ ''name''__=__''value'' Sets a named run-time parameter. Consult the ''Administrator's Guide'' for a list and descriptions. Most of the other command line options are in fact short forms of such a parameter assignment. __-c__ can appear multiple times to set multiple parameters. __-d__ ''debug-level'' Sets the debug level. The higher this value is set, the more debugging output is written to the server log. The default is 0, which means no debugging. Values up to 4 are useful; higher numbers produce no additional output. __-D__ ''datadir'' Specifies the file system location of the data directory. See discussion above. __-F__ Disables __fsync__ calls for performance improvement, at the risk of data corruption in event of a system crash. Read the detailed documentation before using this! __-h__ ''hostname'' Specifies the TCP/IP host name or address on which the __postmaster__ is to listen for connections from client applications. Defaults to listening on all configured addresses (including __localhost__). __-i__ Allows clients to connect via TCP/IP (Internet domain) connections. Without this option, only local Unix domain socket connections are accepted. __-k__ ''directory'' Specifies the directory of the Unix-domain socket on which the __postmaster__ is to listen for connections from client applications. The default is normally ''/tmp'', but can be changed at build time. __-l__ Enables secure connections using SSL. The __-i__ option is also required. You must have compiled with SSL enabled to use this option. __-N__ ''max-connections'' Sets the maximum number of client connections that this __postmaster__ will accept. By default, this value is 32, but it can be set as high as your system will support. (Note that __-B__ is required to be at least twice __-N__. See the ''Administrator's Guide'' for a discussion of system resource requirements for large numbers of client connections.) __-o__ ''extra-options'' The command line-style options specified in ''extra-options'' are passed to all backend server processes started by this __postmaster__. See postgres(1) for possibilities. If the option string contains any spaces, the entire string must be quoted. __-p__ ''port'' Specifies the TCP/IP port or local Unix domain socket file extension on which the __postmaster__ is to listen for connections from client applications. Defaults to the value of the __PGPORT__ environment variable, or if __PGPORT__ is not set, then defaults to the value established during compilation (normally 5432). If you specify a port other than the default port, then all client applications must specify the same port using either command-line options or __PGPORT__. __-S__ Specifies that the __postmaster__ process should start up in silent mode. That is, it will disassociate from the user's (controlling) terminal, start its own process group, and redirect its standard output and standard error to ''/dev/null''. Using this switch discards all logging output, which is probably not what you want, since it makes it very difficult to troubleshoot problems. See below for a better way to start the __postmaster__ in the background. __--__''name''__=__''value'' Sets a named run-time parameter; a shorter form of __-c__. Two additional command line options are available for debugging problems that cause a backend to die abnormally. These options control the behavior of the __postmaster__ in this situation, and __neither option is intended for use in ordinary operation__. The ordinary strategy for this situation is to notify all other backends that they must terminate and then reinitialize the shared memory and semaphores. This is because an errant backend could have corrupted some shared state before terminating. These special-case options are: __-n__ __postmaster__ will not reinitialize shared data structures. A knowledgeable system programmer can then use a debugger to examine shared memory and semaphore state. __-s__ __postmaster__ will stop all other backend processes by sending the signal SIGSTOP, but will not cause them to terminate. This permits system programmers to collect core dumps from all backend processes by hand. __OUTPUTS__ __semget: No space left on device__ If you see this message, you should run the __ipcclean__ command. After doing so, try starting __postmaster__ again. If this still doesn't work, you probably need to configure your kernel for shared memory and semaphores as described in the installation notes. If you run multiple instances of __postmaster__ on a single host, or have a kernel with particularly small shared memory and/or semaphore limits, you may have to reconfigure your kernel to increase its shared memory or semaphore parameters. __Tip:__ You may be able to postpone reconfiguring your kernel by decreasing __-B__ to reduce the shared memory consumption of PostgreSQL, and/or by reducing __-N__ to reduce the semaphore consumption. __!StreamServerPort: cannot bind to port__ If you see this message, you should make certain that there is no other __postmaster__ process already running on the same port number. The easiest way to determine this is by using the command $ __ps ax | grep postmaster __or $ __ps -e | grep postmaster __depending on your system. If you are sure that no other __postmaster__ processes are running and you still get this error, try specifying a different port using the -p option. You may also get this error if you terminate the __postmaster__ and immediately restart it using the same port; in this case, you must simply wait a few seconds until the operating system closes the port before trying again. Finally, you may get this error if you specify a port number that your operating system considers to be reserved. For example, many versions of Unix consider port numbers under 1024 to be ''trusted'' and only permit the Unix superuser to access them. !!NOTES If at all possible, __do not__ use SIGKILL to kill the __postmaster__. This will prevent __postmaster__ from freeing the system resources (e.g., shared memory and semaphores) that it holds before terminating. To terminate the __postmaster__ normally, the signals SIGTERM, SIGINT, or SIGQUIT can be used. The first will wait for all clients to terminate before quitting, the second will forcefully disconnect all clients, and the third will quit immediately without proper shutdown, resulting in a recovery run during restart. The utility command pg_ctl(1) can be used to start and shut down the __postmaster__ safely and comfortably. The __--__ options will not work on FreeBSD or OpenBSD. Use __-c__ instead. This is a bug in the affected operating systems; a future release of PostgreSQL will provide a workaround if this is not fixed. !!USAGE To start __postmaster__ in the background using default values, type: $ __nohup postmaster __To start __postmaster__ with a specific port: $ __postmaster -p 1234 __This command will start up __postmaster__ communicating through the port 1234. In order to connect to this __postmaster__ using psql, you would need to run it as $ __psql -p 1234 __or set the environment variable __PGPORT__: $ __export PGPORT=1234 __$ __psql __Named runtime parameters can be set in either of these styles: $ __postmaster -c sort_mem=1234 __$ __postmaster --sort-mem=1234 __Either form overrides whatever setting might exist for sort_mem in ''postgresql.conf''. Notice that underscores in parameter names can be written as either underscore or dash on the command line. __Tip:__ Except for short-term experiments, it's probably better practice to edit the setting in ''postgresql.conf'' than to rely on a command-line switch to set a parameter. ----
5 pages link to
postmaster(1)
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initdb(1)
ipcclean(1)
pg_ctl(1)
postgres(1)
Man1p
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