pg_dumpall is a utility for writing out ("dumping") all PostgreSQL databases of a cluster into one script file. The script file contains SQL commands that can be used as input to psql to restore the databases. It does this by calling pg_dump for each database in a cluster. pg_dumpall also dumps global objects that are common to all databases. (pg_dump does not save these objects.) This currently includes the information about database users and groups.
Thus, pg_dumpall is an integrated solution for backing up your databases. But note a limitation: it cannot dump "large objects", since pg_dump cannot dump such objects into text files. If you have databases containing large objects, they should be dumped using one of pg_dump's non-text output modes.
Since pg_dumpall reads tables from all databases you will most likely have to connect as a database superuser in order to produce a complete dump. Also you will need superuser privileges to execute the saved script in order to be allowed to add users and groups, and to create databases.
The SQL script will be written to the standard output. Shell operators should be used to redirect it into a file.
pg_dumpall might need to connect several times to the PostgreSQL server, asking for a password each time. It is convenient to have a $HOME/.pgpass file in such cases.
The following command-line options are used to control the output format.
Include SQL commands to clean (drop) the databases before recreating them.
Dump data as INSERT commands (rather than COPY). This will make restoration very slow, but it makes the output more portable to other RDBMS packages.
Dump data as INSERT commands with explicit column names (INSERT INTO table (column, ...) VALUES ...). This will make restoration very slow, but it is necessary if you desire to rearrange column ordering.
Dump only global objects (users and groups), no databases.
Ignore version mismatch between pg_dumpall and the database server.
pg_dumpall can handle databases from previous releases of PostgreSQL, but very old versions are not supported anymore (currently prior to 7.0). Use this option if you need to override the version check (and if pg_dumpall then fails, don't say you weren't warned).
Dump object identifiers (OIDs) for every table. Use this option if your application references the OID columns in some way (e.g., in a foreign key constraint). Otherwise, this option should not be used.
Specifies verbose mode. This will cause pg_dumpall to print progress messages to standard error.
The following command-line options control the database connection parameters.
Specifies the host name of the machine on which the database server is running. If host begins with a slash, it is used as the directory for the Unix domain socket. The default is taken from the PGHOST environment variable, if set, else a Unix domain socket connection is attempted.
The port number on which the server is listening. Defaults to the PGPORT environment variable, if set, or a compiled-in default.
Connect as the given user.
Force a password prompt. This should happen automatically if the server requires password authentication.
Long options are only available on some platforms.
Since pg_dumpall calls pg_dump internally, some diagnostic messages will refer to pg_dump.
pg_dumpall will need to connect several times to the PostgreSQL server. If password authentication is configured, it will ask for a password each time. In that case it would be convenient to set up a password file.
To dump all databases:
$ pg_dumpall > db.out
To reload this database use, for example:
$ psql -f db.out template1
(It is not important to which database you connect here since the script file created by pg_dumpall will contain the appropriate commands to create and connect to the saved databases.)