Step 3: Connect to a DB Instance Through psql

You can use the PostgreSQL client psql to connect to a DB instance through a common connection or an SSL connection. The SSL connection is encrypted and therefore more secure.

Preparations

To connect to a DB instance through an ECS, you need to create an ECS first.
Install the PostgreSQL client on the prepared ECS or device.

Common Connection

Run the following command to connect to the DB instance:

psql --no-readline -U <user> -h <host> -p <port> -d <datastore> -W

**Table 1** Parameter description
Parameter	Description
<user>	Indicates the username of the RDS database account. The default administrator is root.
<host>	Indicates the IP address of the primary DB instance. To obtain this parameter, go to the Basic Information page of the DB instance. If the DB instance is accessed through the ECS, the IP address can be found in the Floating IP Address field in the Connection Information area.
<port>	Indicates the database port in use. The default value is 5432. To obtain this parameter, go to the Basic Information page of the DB instance. The port number can be found in the Database Port field in the Connection Information area.
<datastore>	Indicates the name of the database (the default database name is postgres).

The parameter -W indicates that a password must be entered for the connection. After running this command, you will be prompted to enter a password.

Example:

Run the following command as user root to connect to a DB instance:

psql --no-readline -U root -h 192.168.0.44 -p 5432 -d postgres -W

SSL Connection

Log in to the management console.
Click in the upper left corner and select a region and a project.
Click Service List. Under Database, click Relational Database Service. The RDS console is displayed.
In the DB Information area on the Basic Information page, click in the SSL field to download the root certificate or certificate bundle.
Upload the root certificate to the ECS or save it to the device to be connected to the DB instance.

Import the root certificate to the Linux OS on the ECS. For details, see How Can I Import the Root Certificate to the Windows or Linux OS?

Connect to an RDS DB instance. The Linux OS is used as an example.

psql --no-readline -h <host> -p <port> "dbname=<database> user=<user> sslmode=verify-ca sslrootcert=<ca-file-directory>"

**Table 2** Parameter description
Parameter	Description
<host>	Indicates the IP address of the primary DB instance. To obtain this parameter, go to the Basic Information page of the DB instance. If the DB instance is accessed through the ECS, the IP address can be found in the Floating IP Address field in the Connection Information area.
<port>	Indicates the database port in use. The default value is 5432. To obtain this parameter, go to the Basic Information page of the DB instance. The port number can be found in the Database Port field in the Connection Information area.
<database>	Indicates the name of the database (the default database name is postgres).
<user>	Indicates the username of the RDS database account. The default administrator is root.
<ca-file-directory>	Indicates the directory of the CA certificate for the SSL connection. The certificate should be stored in the directory where the command is executed.
sslmode	Indicates the SSL connection mode. Set it to verify-ca to use a CA to check whether the service is trusted.

Enter the password of the database account if the following information is displayed:

Password:

For example, to connect to a DB instance through an SSL connection as user root, run the following command:

psql --no-readline -h 192.168.0.44 -p 5432 "dbname=postgres user=root sslmode=verify-ca sslrootcert=/root/ca.pem"

Password:

The SSL connection is established if information similar to the following is displayed after you log in to the database:
```
SSL connection (protocol: TLSv1.2, cipher: ECDHE-RSA-AES256-GCM-SHA384, bits: 256, compression: off)
```