While working on different projects and in different environments, we often need to export a dump from one database and then import it into another. A while ago Slobodan wrote how to export and import a mySQL dump, and here is a guide how to backup and restore a PostgreSQL database.

Export a PostgreSQL database dump

To export PostgreSQL database we will need to use the pg_dump tool, which will dump all the contents of a selected database into a single file.
We need to run pg_dump in the command line on the computer where the database is stored. So, if the database is stored on a remote server, you will need to SSH to that server in order to run the following command:

 pg_dump -U db_user -W -F t db_name > /path/to/your/file/dump_name.tar 

Here we used the following options:

  • -U to specify which user will connect to the PostgreSQL database server.
  • -W or --password will force pg_dump to prompt for a password before connecting to the server.
  • -F is used to specify the format of the output file, which can be one of the following:
    • p – plain-text SQL script
    • c – custom-format archive
    • d – directory-format archive
    • t – tar-format archive

custom, directory and tar formats are suitable for input into pg_restore.

To see a list of all the available options use pg_dump -?.

With given options pg_dump will first prompt for a password for the database user db_user and then connect as that user to the database named db_name. After it successfully connects, > will write the output produced by pg_dump to a file with a given name, in this case dump_name.tar.

File created in this process contains all the SQL queries that are required in order to replicate your database.

Import a PostgreSQL database dump

There are two ways to restore a PostgreSQL database:

  1. psql for restoring from a plain SQL script file created with pg_dump,
  2. pg_restore for restoring from a .tar file, directory, or custom format created with pg_dump.

1. Restore a database with psql

If your backup is a plain-text file containing SQL script, then you can restore your database by using PostgreSQL interactive terminal, and running the following command:

psql -U db_user db_name < dump_name.sql

where db_user is the database user, db_name is the database name, and dump_name.sql is the name of your backup file.

2. Restore a database with pg_restore

If you choose custom, directory, or archive format when creating a backup file, then you will need to use pg_restore in order to restore your database:

 pg_restore -d db_name /path/to/your/file/dump_name.tar -c -U db_user 

If you use pg_restore you have various options available, for example:

  • -c to drop database objects before recreating them,
  • -C to create a database before restoring into it,
  • -e exit if an error has encountered,
  • -F format to specify the format of the archive.

Use pg_restore -? to get the full list of available options.

You can find more info on using mentioned tools by running man pg_dump, man psql and man pg_restore.

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