Connecting to a DB Instance Through psql

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

SSL is enabled by default when you create an RDS for PostgreSQL DB instance and cannot be disabled after the instance is created.

You have logged in to the ECS.
- To connect to a DB instance through an ECS, make sure that:
  - The ECS and DB instance must be in the same VPC.
  - The ECS must be allowed by the security group to access RDS DB instances.
    - If the security group with which the target DB instance is associated is the default security group, you do not need to configure security group rules.
    - If the security group with which the target DB instance is associated is not the default security group, check whether the security group rules allow the ECS to connect to the DB instance. For details, see Configuring Security Group Rules.
      If the security group rules allow the access from the ECS, the ECS can connect to the DB instance.
      
      If the security group rules do not allow the access from the ECS, you need to add a security group rule. The ECS must be allowed by the security group to access DB instances.
You have installed a database client to connect to DB instances.
For details, see How Can I Install a PostgreSQL Client?

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.
On the Instance Management page, click the instance name to go to the Basic Information page.
Click next to SSL 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.
For details about how to import the root certificate to the Linux OS on the ECS, see How Can I Import the Root Certificate to a 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 1** Parameter description
Parameter	Description
<host>	IP address of the primary DB instance. To obtain this parameter value, go to the Basic Information page of the DB instance and view the floating IP address in the Connection Information area (if the DB instance is to be accessed through an ECS).
<port>	Database port in use. The default value is 5432. To obtain this parameter value, 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>	Name of the database (the default database name is postgres).
<user>	Username of the RDS database account. The default administrator is root.
<ca-file-directory>	Directory of the CA certificate for the SSL connection. The certificate should be stored in the directory where the command is executed.
sslmode	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)
```