Simple connection with PostgreSQL

1. Running a Container and Configuring PostgreSQL

• PostgreSQL containers run based on the postgres image.
  • You can set admin username, password, and initial database name using environment variables when starting the container.
• Example

# Run PostgreSQL 15
docker run -d \
  --name pg-container \
  -e POSTGRES_USER=admin \
  -e POSTGRES_PASSWORD=admin123 \
  -e POSTGRES_DB=mydb \
  -p 15432:5432 \
  postgres:15

• Options
  • -d → Detached (background) mode
  • --name → Container name
  • -e → Environment variables (admin user, password, initial DB)
  • -p → Host:Container port mapping
• Windows Notes
  • CMD: use ^ as line continuation
  • PowerShell: use ₩ as line continuation
• Tips
  • Store passwords in a .env file for security
  • Mount a host directory with -v to persist data even if the container is deleted.

Option	Description
-e POSTGRES_USER	Admin username
-e POSTGRES_PASSWORD	Admin password
-e POSTGRES_DB	Initial database name
-p	Port mapping

2. Accessing the Container and Checking the DB

1. Access Container Terminal
   • docker exec -it pg-container bash
2. Connect with PostgreSQL Client
   • psql -U admin -d mydb
3. DB Status Commands

-- Check PostgreSQL version
SELECT version();
 
-- List all databases
\l
 
-- List all tables
\dt

• Tips
  • You can run commands directly from outside the container:
  • docker exec -it pg-container psql -U admin -d mydb

Command	Description
docker exec -it <container> bash	Access container terminal
psql -U <user> -d <db>	Connect to PostgreSQL
SQL commands	Check DB status and data

3. Connecting Externally

• Because the container exposes a port with -p 5432:5432, you can connect from your local terminal or a GUI client like DataGrip.

Local Terminal Connection

psql -h localhost -p 5432 -U admin -d mydb

• -h → host (localhost)
• -p → port
• -U → username
• -d → database name

DataGrip Connection

1. Open DataGrip → New Database Connection → PostgreSQL
2. Host: localhost
3. Port: 5432
4. User: admin
5. Password: admin123
6. Database: mydb
7. Test connection → OK

If connection fails, check firewall settings or port conflicts.

4. Monitoring Logs

• PostgreSQL container logs show server start/stop events, connections, and errors.

Commands

# Show all logs
docker logs pg-container
 
# Follow logs in real time
docker logs -f pg-container

• Use -f for real-time monitoring during development.
• In production, collect logs to external files or monitoring systems.

Command	Description
docker logs	Show all logs
docker logs -f	Real-time log monitoring