How to change the TCP port number of Postgresql in the firewall

Question

Hi,
I will explain the problem in detail. I have a web application deployed over https in my production environment on Amazon. This application uses a Postgresql database on port 5432. The application has been working correctly since the beginning and it's been over 3 years. However, for a few days I could no longer access my application. I then checked the database and realized that Postgresql was no longer working on port 5432. I then restarted the port with the service postgresql restart command and suddenly the application worked again. But the next day, the problem returned and I restarted Postgres but this time the database refused to start.
So I'm now trying to modify Postgresql port 5432 to see if that would solve my problem. And since I opened the port in my Amazon instance, that's where I should be able to modify it, which I can't.
 IF I run this command sudo -u postgres psql,  I GET ERROR:
psql: error: connection to server on socket "/var/run/postgresql/.s.PGSQL.5432" failed: No such file or directory
        Is the server running locally and accepting connections on that socket?

Accepted Answer

I doubt that changing the port will make any difference...

You may want to review the memory usage of the EC2 and see if its being exhausted. You may also want to review the Server logs to see why its stopping.

Answer

- Verify Port Status: Before attempting to modify the port, confirm whether port 5432 is currently open or closed. You can use tools like telnet, netstat, or firewall management interfaces to check the port status.

- Check for Conflicts: Ensure that there are no other applications or services currently using port 5432. Port conflicts can prevent PostgreSQL from binding to the specified port.

-here's a step-by-step guide to changing the TCP port number for PostgreSQL in Linux:

Check Current Port Configuration:
First, confirm the current port configuration for PostgreSQL. You can typically find this information in the PostgreSQL configuration file (postgresql.conf). Look for the port directive. Alternatively, you can use the netstat command to check which port PostgreSQL is currently listening on:
`netstat -tuln | grep postgres`

Identify Firewall Software:
Determine which firewall software you are using on your Linux system. Common firewall software on Linux includes iptables (legacy) and firewalld (more common in recent distributions). You'll use different commands depending on the firewall software.

Modify Firewall Rules:
Let's assume you're using firewalld which is common on modern Linux distributions like Fedora, CentOS, and RHEL. To modify the firewall rules, first, identify the service associated with PostgreSQL:
`firewall-cmd --get-services | grep postgres`

Open New Port:
If there isn't a predefined service for PostgreSQL, you can manually add the port:
`firewall-cmd --zone=public --add-port=5432/tcp --permanent`

Reload Firewall Configuration:
After adding the new port, reload the firewall configuration to apply the changes:
`firewall-cmd --reload`

Verify Changes:
Check if the new port is now open in the firewall:
`firewall-cmd --zone=public --list-ports`

Update PostgreSQL Configuration:
Open the PostgreSQL configuration file (postgresql.conf) with a text editor like nano or vi:
`sudo nano /etc/postgresql//main/postgresql.conf`
Find the port directive and change the port number to 5432 or the new port you specified.

Restart PostgreSQL Service:
After updating the configuration, restart the PostgreSQL service for the changes to take effect:
`sudo systemctl restart postgresql`

Test Connectivity:
Verify that PostgreSQL is now listening on the new port:
`netstat -tuln | grep postgres`
Additionally, test connectivity to PostgreSQL from remote hosts using the new port.

How to change the TCP port number of Postgresql in the firewall

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