pg_createcluster

pg_createcluster - create a new PostgreSQL cluster

pg_createcluster creates a new PostgreSQL server cluster (i. e. a collection of databases served by a postmaster(1) instance) and integrates it into the multi-version/multi-cluster architecture of the postgresql-common package.

Every cluster is uniquely identified by its version and name. The name can be arbitrary. The default cluster that is created on installation of a server package is CWmain. However, you might wish to create other clusters for testing, with other superusers, a cluster for each user on a shared server, etc. CWpg_createcluster will abort with an error if you try to create a cluster with a name that already exists for that version.

Given a major PostgreSQL version (like “7.4” or “8.0”) and a cluster name, it creates the necessary configuration files in CW/etc/postgresql/versionCW/nameCW/; in particular these are CWpostgresql.conf, CWpg_ident.conf, CWpg_hba.conf, a postgresql-common specific configuration file CWstart.conf (see \s-1STARTUP\s0 \s-1CONTROL\s0 below), a symbolic link CWpgdata which points to the actual data directory data dir (which defaults to CW/var/lib/postgresql/versionCW/nameCW/), and a symbolic link CWlog which points to the log file (by default, CW/var/log/postgresql/postgresql-versionCW-nameCW.log).

To enable easy integration of pg_autovacuum for Servers prior to 8.1, this program also creates a symbolic link CWautovacuum_log which points to the pg_autuvacuum log file (by default, CW/var/log/postgresql/pg_autovacuum-versionCW-nameCW.log). PostgreSQL 8.1 and later has an integrated autovacuuming which does not need this.

CWpostgresql.conf is automatically adapted to use the next available port, i. e. the first port (starting from 5432) which is not yet used by an already existing cluster.

If the data directory does not yet exist, PostgreSQL's initdb(1) command is used to generate a new cluster structure. If the data directory already exists, it is integrated into the postgresql-common structure by moving the configuration file and creating the CWpgdata link.

If a custom socket directory is given and it does not exist, it is created.

If the log file does not exist, it is created. In any case the permissions are adjusted to allow write access to the cluster owner. Please note that CWpostgresql.conf can be customized to specify CWlog_directory and/or CWlog_filename; if at least one of these options is present, then the symbolic link CWlog in the cluster configuration directory is ignored.

If the default snakeoil \s-1SSL\s0 certificate exists (CW/etc/ssl/certs/ssl-cert-snakeoil.pem and CW/etc/ssl/private/ssl-cert-snakeoil.key), this program creates symlinks to these files in the data directory (CWserver.crt and CWserver.key) and enables \s-1SSL\s0 for that cluster (option ssl in CWpostgresql.conf). Therefore all clusters will use the same \s-1SSL\s0 certificate by default. Of course you can replace these symlinks with a cluster specific certificate.

"-u Set the user who owns the cluster and becomes the database superuser to the given name or uid. By default, this is the user postgres. A cluster must not be owned by root.

"-g Change the group of the cluster related data files. By default this will be the primary group of the database owner.

"-d Explicitly set the data directory path, which is used to store all the actual databases and tables. This will become quite big (easily in the order of five times the amount of actual data stored in the cluster). Defaults to CW/var/lib/postgresql/versionCW/cluster.

"-s Explicitly set the directory where the postmaster(1) server stores the Unix socket for local connections. Defaults to CW/var/run/postgresql/ for clusters owned by the user postgres, and CW/tmp for clusters owned by other users. Please be aware that CW/tmp is an unsafe directory since everybody can create a socket there and impersonate the database server. If the given directory does not exist, it is created with appropriate permissions.

"-l Explicitly set the path for the postmaster(1) server log file. Defaults to CW/var/log/postgresql/postgresql-versionCW-clusterCW.log.

"--locale=locale" Set the default locale for the database cluster. If this option is not specified, the locale is inherited from the environment that pg_createcluster runs in.

"--lc-collate=locale"

"--lc-ctype=locale"

"--lc-messages=locale"

"--lc-monetary=locale"

"--lc-numeric=locale"

"--lc-time=locale"

Like --locale, but only sets the locale in the specified category.

"-e Select the encoding of the template database. This will also be the default encoding of any database you create later, unless you override it there. The default is derived from the locale, or \s-1SQL_ASCII\s0 if that does not work. The character sets supported by the PostgreSQL server are described in the documentation. Note: It is not recommended to set this option directly! Set the locale instead.

"-p Select the port the new cluster listens on (for the Unix socket and the \s-1TCP\s0 port); this must be a number between 1024 and 65535, since PostgreSQL does not run as root and thus needs an unprivileged port number. By default the next free port starting from 5432 is assigned.

"--start" Immediately start a server for the cluster after creating it (i. e. call CWpg_ctlcluster version cluster CWstart on it). By default, the cluster is not started.

"--start-conf=auto|manual|disabled" Set the initial value in the CWstart.conf configuration file. See \s-1STARTUP\s0 \s-1CONTROL\s0 below. By default, auto is used, which means that the cluster is handled by CW/etc/init.d/postgresql-version, i. e. starts and stops automatically on system boot.

The CWstart.conf file in the cluster configuration directory controls the start/stop behavior of that cluster's postmaster process. The file can contain comment lines (started with '#'), empty lines, and must have exactly one line with one of the following keywords:

"auto" The postmaster process is started/stopped automatically in the init script. This is also the default if the file is missing.

"manual" The postmaster process is not handled by the init script, but manually controlling the cluster with pg_ctlcluster(1) is permitted.

"disable" Neither the init script nor pg_ctlcluster(1) are permitted to start/stop the cluster. Please be aware that this will not stop the cluster owner from calling lower level tools to control the postmaster process; this option is only meant to prevent accidents during maintenance, not more.

Martin Pitt <mpitt@debian.org>