pg_createcluster - Online in the Cloud

PROGRAM:

NAME

pg_createcluster - create a new PostgreSQL cluster

SYNOPSIS

pg_createcluster [options] version name [-- initdb options]

DESCRIPTION

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 main. However,
you might wish to create other clusters for testing, with other superusers, a cluster for
each user on a shared server, etc. pg_createcluster will abort with an error if you try to
create a cluster with a name that already exists for that version.

For compatibility with systemd service units, the cluster name should not contain any
dashes (-). pg_ctlcluster will warn about the problem, but succeed with the operation.

Given a major PostgreSQL version (like "8.2" or "8.3") and a cluster name, it creates the
necessary configuration files in /etc/postgresql/version/name/; in particular these are
postgresql.conf, pg_ident.conf, pg_hba.conf, a postgresql-common specific configuration
file start.conf (see STARTUP CONTROL below), pg_ctl.conf, and a symbolic link log which
points to the log file (by default, /var/log/postgresql/postgresql-version-name.log).

postgresql.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 setting the
data_directory option. Please note that this only works for data directories which were
created directly with initdb, i. e. all the configuration files (postgresql.conf etc.)
must be present in the data directory.

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 postgresql.conf can be
customized to specify log_directory and/or log_filename; if at least one of these options
is present, then the symbolic link log in the cluster configuration directory is ignored.

If the default snakeoil SSL certificate exists (/etc/ssl/certs/ssl-cert-snakeoil.pem and
/etc/ssl/private/ssl-cert-snakeoil.key), and the postgres user is in the ssl-cert Unix
group, pg_createcluster configures the cluster to use this certificate, and enables SSL.
Therefore all clusters will use the same SSL certificate by default. For versions up to
9.1, symlinks in the data directory will be created (server.crt and server.key); for 9.2
and later, the appropriate postgresql.conf options will be set (ssl_cert_file and
ssl_key_file). Of course you can replace this with a cluster specific certificate.
Similarly for /etc/postgresql-common/root.crt and /etc/postgresql-common/root.crl, these
files will be configured as client certificate CA and revocation list, when present.
(root.crt is initially a placeholder that will only be used if real certificates are added
to the file.)

OPTIONS

-u user, --user=user
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 group, --group=group
Change the group of the cluster related data files. By default this will be the
primary group of the database owner.

-d dir, --datadir=dir
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
/var/lib/postgresql/version/cluster.

-s dir, --socketdir=dir
Explicitly set the directory where the postmaster(1) server stores the Unix socket for
local connections. Defaults to /var/run/postgresql/ for clusters owned by the user
postgres, and /tmp for clusters owned by other users. Please be aware that /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 path, --logfile=path
Explicitly set the path for the postmaster(1) server log file. Defaults to
/var/log/postgresql/postgresql-version-cluster.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 encoding, --encoding=encoding
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 SQL_ASCII 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 port, --port=port
Select the port the new cluster listens on (for the Unix socket and the TCP 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 pg_ctlcluster
version cluster start on it). By default, the cluster is not started.

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

-o guc=value, --pgoption guc=value
Configuration option to set in the new postgresql.conf file.

--createclusterconf=file
Alternative createcluster.conf file to use. Default is
/etc/postgresql-common/createcluster.conf (or $PGSYSCONFDIR/createcluster.conf).

--environment=file
Alternative default environment file to use. Default is
/etc/postgresql-common/environment (or $PGSYSCONFDIR/environment). If the file is
missing, a placeholder string is used. %v and %c are replaced; see DEFAULT VALUES
below.

-- initdb options
Options passed directly to initdb(1).

Per default, pg_createcluster will update the pg_hba.conf file generated by initdb to
use peer authentication on local (unix) connections, and md5 on TCP (host)
connections. If explicit authentication config is included here (-A, --auth,
--auth-host, --auth-local), the pg_hba.conf file will be left untouched.

STARTUP CONTROL

The start.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.

disabled
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.

The pg_ctl.conf file in the cluster configuration directory can contain additional options
passed to pg_ctl of that cluster.

DEFAULT VALUES

Some default values used by pg_createcluster can be modified in
/etc/postgresql-common/createcluster.conf. Occurrences of %v are replaced by the major
version number, and %c by the cluster name. Use %% for a literal %.

create_main_cluster (Default: true)
Create a main cluster when a new postgresql-x.y server package is installed.

start_conf (Default: auto)
Default start.conf value to use.

data_directory (Default: /var/lib/postgresql/%v/%c)
Default data directory.

xlogdir (Default: unset)
Default directory for transaction logs. When used, initdb will create a symlink from
pg_xlog in the data directory to this location. Unset by default, i.e. pg_xlog is
remains in the data directory.

initdb_options (Default: unset)
Other options to pass to initdb.

Other options
All other options listed are copied into the new cluster's postgresql.conf, e.g.:

listen_addresses = '*'
log_line_prefix = '%%t '

Some postgresql.conf options are treated specially:

ssl Only added to postgresql.conf if the default snakeoil certificates exist and are
readable for the cluster owner as detailed above.

stats_temp_directory
Only added to postgresql.conf if existing, and writable for the cluster owner, or
else if the parent directory is writable.

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