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postgres *- run the Postgres backend directly
postgres [-Q] [databasename] [-d debug_level]
This command executes the POSTGRES backend directly. This should be done only while debugging by the DBA, and should not be done while other POSTGRES backends are being managed by a postmaster on this set of databases.
-Q indicates "Quiet" mode. By default, the POSTGRES backend prints the parse tree generated by the parser, the plan generated by the planner and many debugging message. Specifying this flag eliminates much of this.
databasename is the name of the database to be used. If this is not specified, databasename defaults to the value of the environment variable USER.
There are several other options that may be specified, used mainly for debugging purposes. These are listed here only for the use of POSTGRES system developers.
-O indicates that the backend should not use the transaction system. All commands run in the same transaction and all commands can see the results of prior commands.
-M nnn indicates that the backend should fork nnn slave backend processes and then execute queries in parallel. This is only useful on shared-memory multiprocessor systems (e.g. Sequent) and is still in experimental and research stage. It is especially unreliable for large joins. Full support for intra-query as well inter-query parallelism have been planned for Version 4.
-S indicates that the transaction system can run with the assumption of stable main memory thus avoiding the necessary flushing of data and log pages to disk at the end of each transaction system. This is only used for performance comparisons for stable vs. non-stable storage. Do not use this in other cases, as recovery after a system crash may be impossible when -S is specified in the absence of stable main memory.
-s indicates that time information and other statistics are to be displayed at the end of each query. This is useful for benchmarking or for use in tuning the number of buffers.
-B nnn indicates the number of shared buffers to use. The default number of buffers is 64.
-s POSTGRES will report execution statistics such as elapse time, buffer hit rate, etc for each query execution.
-L this flag will turn off locking.
semget: No space left on device
If you see this message, you should run the ipcclean command. After doing this, try running POSTGRES again. If this still doesn't work, you will need to configure your kernel for shared memory and semaphores as described in the installation notes.
monitor(unix), postmaster(unix), ipcclean(unix).