PostgreSQL is a flexible relational database that is used in various environments. It can be used in local development to complex production systems. However, identifying the port on which PostgreSQL is running is important especially if multiple data instances, network configuration, and troubleshooting issues are involved.
By default, PostgreSQL listens on port 5432, but this can be customized based on specific needs. This guide provides detailed guidance on how to tell what port Postgres is running on across different platforms, configurations, and tools.
Understanding PostgreSQL’s Default Port and Configurability
By default, PostgreSQL is set to listen on port 5432. This port is configured in the `postgresql.conf` file, which serves as the main configuration file for PostgreSQL’s settings. When running multiple PostgreSQL instances on a single machine, each instance must be assigned a unique port to avoid conflicts. Here’s how to check for the port using the `postgresql.conf` file and several other methods depending on your access and operating system.
Finding the Port in the `postgresql.conf` File
The `postgresql.conf` file is the first place to check when you need to find PostgreSQL ports. It’s located in the data directory of your PostgreSQL installation, which varies by operating system and installation method.
Locate the Configuration File
Linux (Debian/Ubuntu): `/etc/postgresql/<version>/main/postgresql.conf`
Linux (RedHat/CentOS): `/var/lib/pgsql/data/postgresql.conf`
Windows: `C:\Program Files\PostgreSQL\<version>\data\postgresql.conf`
macOS (Homebrew): `/usr/local/var/postgres/postgresql.conf`
Open the Configuration File
Open `postgresql.conf` in a text editor. On Linux, you might use:
“`bash
sudo nano /etc/postgresql/<version>/main/postgresql.conf
“`
Locate the Port Setting
Within `postgresql.conf`, look for the following line:
“`plaintext
port = 5432
“`
If this line is commented out (preceded by a `#`), PostgreSQL is typically defaulting to port 5432 unless overridden.
This file allows you to change the port by simply editing the value and restarting PostgreSQL.
Checking the Port via SQL Query with `psql`
If you’re able to connect to PostgreSQL using `psql` or another SQL client, you can check the current port setting directly with a SQL query.
Connect to PostgreSQL with `psql`
“`bash
psql -U postgres -d your_database_name
“`
Run a Query to Check the Port
Once connected, execute:
“`sql
SHOW port;
“`
PostgreSQL will return the port number used by the current instance. This method is especially useful for remote connections where you can’t directly access configuration files.
Using Network Utilities like `netstat` or `ss` to Find the Port
If PostgreSQL is running, you can use network utility commands like `netstat` or `ss` to identify the port.
Using `netstat`
The `netstat` command lists active network connections, including the ports they are listening on.
“`bash
sudo netstat -plnt | grep postgres
“`
`-p` shows the process name, `-l` lists listening ports, `-n` shows numerical addresses, and `-t` lists TCP connections.
The output will show lines where PostgreSQL is listening. Look for an entry similar to `127.0.0.1:5432`, indicating the IP and port.
Using `ss` (Linux)
`ss` is a modern replacement for `netstat` and offers a similar way to check listening ports.
“`bash
sudo ss -plnt | grep postgres
“`
This command should return a line like `127.0.0.1:5432` or similar if PostgreSQL is listening on port 5432.
Checking the Port in the `pg_hba.conf` File
The `pg_hba.conf` file configures authentication and can also provide clues about network configurations. While it doesn’t directly define the port, it includes IP addresses and authentication methods that can confirm which connections PostgreSQL will accept.
Locate and Open `pg_hba.conf`
“`bash
sudo nano /etc/postgresql/<version>/main/pg_hba.conf
“`
Examine the `host` Entries
Entries with `host` or `hostssl` typically represent remote access. This can help confirm which IP configurations PostgreSQL is using for connections, although the port is defined elsewhere.
Using Service Management Commands
PostgreSQL is often managed as a service, especially in production environments. This method allows you to query the service status and sometimes obtain port details.
Using `systemctl` on Linux
For systems using `systemd`, you can check PostgreSQL’s status as follows:
“`bash
sudo systemctl status postgresql
“`
This command will provide information on whether PostgreSQL is active, which configuration it’s using, and sometimes the port.
Using Homebrew on macOS
If you installed PostgreSQL using Homebrew on macOS, you can check the status with:
“`bash
brew services list | grep postgres
“`
Windows Services
In Windows, open the Services application by typing `services.msc` in the Run dialog. Locate PostgreSQL in the list, right-click, and check Properties. Although this does not directly display the port, it shows the status and additional configuration details, which can help in locating the port.
Environment Variables
Some PostgreSQL instances are configured to use environment variables for port settings, particularly in containerized or cloud environments.
Check Environment Variables on Linux/macOS
“`bash
env | grep PGPORT
“`
If the `PGPORT` variable is set, it will display the port value. This is common in environments where PostgreSQL instances are dynamically configured at runtime.
Check Environment Variables on Windows
Open Command Prompt or PowerShell and use:
“`powershell
echo %PGPORT%
“`
If `PGPORT` is set, this command will print the port.
Analyzing Application Logs
PostgreSQL logs contain startup messages that often include the port. Checking these logs can reveal the port, particularly if other methods are inaccessible.
Locate PostgreSQL Logs
On Linux, PostgreSQL logs are often in `/var/log/postgresql/`.
On Windows, look in the `pg_log` directory within the PostgreSQL installation directory.
Search the Logs for Port Information
Open the log file and look for lines like:
“`plaintext
LOG: database system is ready to accept connections on port 5432
“`
These messages are logged each time PostgreSQL starts and confirms the active port.
Automating Port Detection with a Script
If you frequently need to check PostgreSQL’s port, consider using a script to automate this. Here’s an example of a Bash script for Linux/macOS:
“`bash
#!/bin/bash
PORT=$(psql -U postgres -tAc “SHOW port”)
if [ -n “$PORT” ]; then
echo “PostgreSQL is running on port: $PORT”
else
echo “Unable to detect PostgreSQL port.”
fi
“`
This script attempts to connect to PostgreSQL and retrieve the port setting, making it a quick way to identify the port in a controlled environment.
Conclusion
How to tell what port Postgres is running on is critical for managing database access, troubleshooting connection issues, and configuring network security. By checking `PostgreSQL.conf`, using network tools, exploring service configurations, and analyzing logs, you can reliably identify the port on which PostgreSQL is listening. Following these steps ensures that you can manage PostgreSQL efficiently, whether in local development or complex production environments.
