freenas/postgres Docker 镜像 - 轩辕镜像 | Docker 镜像高效稳定拉取服务

What is PostgreSQL?

PostgreSQL, often simply "Postgres", is an object-relational database management system (ORDBMS) with an emphasis on extensibility and standards-compliance. As a database server, its primary function is to store data, securely and supporting best practices, and retrieve it later, as requested by other software applications, be it those on the same computer or those running on another computer across a network (including the Internet). It can handle workloads ranging from small single-machine applications to large Internet-facing applications with many concurrent users. Recent versions also provide replication of the database itself for security and scalability.

PostgreSQL implements the majority of the SQL:2011 standard, is ACID-compliant and transactional (including most DDL statements) avoiding locking issues using multiversion concurrency control (MVCC), provides immunity to dirty reads and full serializability; handles complex SQL queries using many indexing methods that are not available in other databases; has updateable views and materialized views, triggers, foreign keys; supports functions and stored procedures, and other expandability, and has a large number of extensions written by third parties. In addition to the possibility of working with the major proprietary and open source databases, PostgreSQL supports migration from them, by its extensive standard SQL support and available migration tools. And if proprietary extensions had been used, by its extensibility that can emulate many through some built-in and third-party open source compatibility extensions, such as for Oracle.

How to use this image

start a postgres instance

• POSTGRES_PASSWORD=mysecretpassword

This image includes EXPOSE 5432 (the postgres port), so standard container linking will make it automatically available to the linked containers. The default postgres user and database are created in the entrypoint with initdb.

The postgres database is a default database meant for use by users, utilities and third party applications.
postgresql.org/docs

connect to it from an application

The easiest and best way to do this is simply to put the application container(s) and this container on their own docker network.

Environment Variables

The PostgreSQL image uses several environment variables which are easy to miss. While none of the variables are required, they may significantly aid you in using the image.

POSTGRES_PASSWORD

This environment variable is recommended for you to use the PostgreSQL image. This environment variable sets the superuser password for PostgreSQL. The default superuser is defined by the POSTGRES_USER environment variable. In the above example, it is being set to "mysecretpassword".

POSTGRES_USER

This optional environment variable is used in conjunction with POSTGRES_PASSWORD to set a user and its password. This variable will create the specified user with superuser power and a database with the same name. If it is not specified, then the default user of postgres will be used.

PGDATA

This optional environment variable can be used to define another location - like a subdirectory - for the database files. The default is /var/lib/postgresql/data, but if the data volume you're using is a fs mountpoint (like with GCE persistent disks), Postgres initdb recommends a subdirectory (for example /var/lib/postgresql/data/pgdata ) be created to contain the data.

POSTGRES_DB

This optional environment variable can be used to define a different name for the default database that is created when the image is first started. If it is not specified, then the value of POSTGRES_USER will be used.

POSTGRES_INITDB_ARGS

This optional environment variable can be used to send arguments to postgres initdb. The value is a space separated string of arguments as postgres initdb would expect them. This is useful for adding functionality like data page checksums: POSTGRES_INITDB_ARGS="--data-checksums".

How to extend this image

If you would like to do additional initialization in an image derived from this one, add one or more *.sql or *.sh scripts under /docker-entrypoint-initdb.d (creating the directory if necessary). After the entrypoint calls initdb to create the default postgres user and database, it will run any *.sql files and source any *.sh scripts found in that directory to do further initialization before starting the service.

For example, to add an additional user and database, add the following to /docker-entrypoint-initdb.d/init-user-db.sh:

bash
#!/bin/bash
set -e

psql -v ON_ERROR_STOP=1 --username "$POSTGRES_USER" <<-EOSQL
	CREATE USER docker;
	CREATE DATABASE docker;
	GRANT ALL PRIVILEGES ON DATABASE docker TO docker;
EOSQL

These initialization files will be executed in sorted name order as defined by the current locale, which defaults to en_US.utf8. Any *.sql files will be executed by POSTGRES_USER, which defaults to the postgres superuser. It is recommended that any psql commands that are run inside of a *.sh script be executed as POSTGRES_USER by using the --username "$POSTGRES_USER" flag. This user will be able to connect without a password due to the presence of trust authentication for Unix socket connections made inside the container.

You can also extend the image with a simple Dockerfile to set a different locale. The following example will set the default locale to de_DE.utf8:

dockerfile
FROM postgres:9.4
RUN localedef -i de_DE -c -f UTF-8 -A /usr/share/locale/locale.alias de_DE.UTF-8
ENV LANG de_DE.utf8

Since database initialization only happens on container startup, this allows us to set the language before it is created.

Caveats

If there is no database when postgres starts in a container, then postgres will create the default database for you. While this is the expected behavior of postgres, this means that it will not accept incoming connections during that time. This may cause issues when using automation tools, such as docker-compose, that start several containers simultaneously.