PostgreSQL - Connect with CLI – Articles

Learn how to connect to a PostgreSQL database instance with a Command Line Interface (CLI).

Managed Databases (also called Cloud Databases) allow you to focus on building and deploying cloud applications while OVHcloud takes care of the database infrastructure and maintenance in operational conditions.

Requirements

a Public Cloud project in your OVHcloud account
access to the OVHcloud Control Panel
a PostgreSQL database running on your OVHcloud Cloud Databases (this guide can help you to meet this requirement)
configure your PostgreSQL instance to accept incoming connections

Concept

A PostgreSQL instance can be managed in multiple ways. One of the easiest, yet powerful ways, is to use a Command Line Interface (CLI), also known as a Console or Terminal.

To interact correctly with the PostgreSQL instance, we need to first install something called a PostgreSQL client, to connect and control the PostgreSQL service remotely. It's a Client-Server interaction.

Instructions

Installing the PostgreSQL client

Please note that PostgreSQL-Client is natively integrated into the PostgreSQL software package.

You first need to install software to interact with your PostgreSQL instance remotely. This official software can be installed on various client machines such as your own computer, a VPS, or a virtual machine. The only rule is to reach the public network (Internet) and have sufficient rights to install it.

To do this, and depending on your configuration, you may need to follow official PostgreSQL documentation to install the PostgreSQL client (referred to as psql).

Follow these steps after selecting Windows, MacOS, or Linux as the operating system.

As explained, the postgresql-client is often included by default.

Example with Linux/Debian:

We will now follow official PostgreSQL documentation to perform our first connection.

In your CLI, type psql --version. The result should look like this:

$ psql --version
psql (PostgreSQL) 13.4 (Ubuntu 13.4-1))

It means that psql is correctly installed and working properly. If you do not see something like this result, please go back to the previous step and reinstall the PostgreSQL client.

Connect to your PostgreSQL instance

We will follow the official PostgreSQL documentation.

To perform a connection, simply type psql followed by the Service URI copied before:

$psql "postgres://<username>:<password>@<hostname>:<port>/defaultdb?sslmode=require"

Don't forget that you need to modify the username, password, hostname, and port. In our example, it will look like this:

$psql "postgre://avnadmin:Mysup3rs3cur3p4ssw0rd@postgresql-ab123456-cd7891011.database.cloud.ovh.us:20184/defaultdb?sslmode=require"

Once connected correctly, you should see something similar to the following:

psql (13.4 (Ubuntu 13.4-1))
SSL connection (protocol: TLSv1.3, cipher: TLS_AES_256_GCM_SHA384, bits: 256, compression: off)
Type "help" for help.

defaultdb=>

Congratulations! You are now fully able to interact with your PostgreSQL instance!

PostgreSQL client usage

Once connected, you can manage your PostgreSQL instance with built-in PostgreSQL client methods.

Please follow the official PostgreSQL documentation.

To verify:

\h CREATE DATABASE will display help on a specific command (here for CREATE DATABASE);
\l+ will list all the databases;
select * from pg_user; will display information about existing users.

In our example, it will look like this:

defaultdb= \h CREATE DATABASE
Command:     CREATE DATABASE
Description: create a new database
Syntax:
CREATE DATABASE name
    [ [ WITH ] [ OWNER [=] user_name ]
           [ TEMPLATE [=] template ]
           [ ENCODING [=] encoding ]
           [ LOCALE [=] locale ]
           [ LC_COLLATE [=] lc_collate ]
           [ LC_CTYPE [=] lc_ctype ]
           [ TABLESPACE [=] tablespace_name ]
           [ ALLOW_CONNECTIONS [=] allowconn ]
           [ CONNECTION LIMIT [=] connlimit ]
           [ IS_TEMPLATE [=] istemplate ] ]

URL: https://www.postgresql.org/docs/13/sql-createdatabase.html

defaultdb= \l+
                                                                List of databases
   Name    |  Owner   | Encoding |   Collate   |    Ctype    |   Access privileges   |  Size   | Tablespace |            Description
-----------+----------+----------+-------------+-------------+-----------------------+---------+------------+------------------------------------
 _aiven    | postgres | UTF8     | en_US.UTF-8 | en_US.UTF-8 |                       | 8269 kB | pg_default |
 defaultdb | avnadmin | UTF8     | en_US.UTF-8 | en_US.UTF-8 |                       | 12 MB   | pg_default |
 template0 | postgres | UTF8     | en_US.UTF-8 | en_US.UTF-8 | =c/postgres          +| 8253 kB | pg_default | unmodifiable empty database
           |          |          |             |             | postgres=CTc/postgres |         |            |
 template1 | postgres | UTF8     | en_US.UTF-8 | en_US.UTF-8 | =c/postgres          +| 8229 kB | pg_default | default template for new databases
           |          |          |             |             | postgres=CTc/postgres |         |            |
(4 rows)

defaultdb= select * from pg_user;
  usename  | usesysid | usecreatedb | usesuper | userepl | usebypassrls |  passwd  | valuntil | useconfig
-----------+----------+-------------+----------+---------+--------------+----------+----------+-----------
 postgres  |       10 | t           | t        | t       | t            | ******** |          |
 _aiven    |    16399 | f           | t        | t       | f            | ******** |          |
 avnadmin  |    16400 | t           | f        | t       | t            | ******** |          |
(3 rows)

Go further

For more information and tutorials, please see our other Cloud Databases support guides or explore the guides for other OVHcloud products and services.

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