Running PostgreSQL Docker Containers

1. Install Docker

Make sure you have Docker installed on your machine. You can download it from the official Docker website.

2. Pull the PostgreSQL Docker Image

Open your terminal and run the following command to pull the latest PostgreSQL image:

docker pull postgres

3. Run a PostgreSQL Container

You can start a new PostgreSQL container with the following command:

docker run --name my_postgres -e POSTGRES_PASSWORD=mysecretpassword -d -p 5432:5432 postgres

--name my_postgres: Names the container my_postgres.
-e POSTGRES_PASSWORD=mysecretpassword: Sets the password for the postgres user.
-d: Runs the container in detached mode.
-p 5432:5432: Maps port 5432 of the container to port 5432 on your host.

4. Accessing PostgreSQL

You can access PostgreSQL using a command-line tool like psql, or through GUI tools like pgAdmin.

Using `psql`:

You can access the PostgreSQL command line interface directly from your terminal:

docker exec -it my_postgres psql -U postgres

5. Create a Database

Once inside the psql shell, you can create a new database:

CREATE DATABASE mydatabase;

6. Using Docker Compose (Optional)

If you want to manage your PostgreSQL setup more easily, consider using Docker Compose. Create a docker-compose.yml file:

version: '3.8'
services:
  db:
    image: postgres
    restart: always
    environment:
      POSTGRES_USER: postgres
      POSTGRES_PASSWORD: mysecretpassword
      POSTGRES_DB: mydatabase
    ports:
      - "5432:5432"

Then run:

docker-compose up -d

7. Persisting Data

By default, data in a Docker container is ephemeral. To persist your PostgreSQL data, you can mount a volume:

docker run --name my_postgres -e POSTGRES_PASSWORD=mysecretpassword -d -p 5432:5432 -v pgdata:/var/lib/postgresql/data postgres

When you stop a Docker container that uses a volume for data storage, the data remains intact and can be accessed even after the container is stopped or removed. Here’s how you can access the storage again:

Steps to Access the Storage Again:

Stop the Container (if not already stopped)
If your container is still running, you can stop it with:
```
 docker stop my_postgres
```
Restart the Container
To access the data again, simply restart the container using the same volume:
```
 docker start my_postgres
```
After restarting, you can access your PostgreSQL data as before.
Accessing PostgreSQL
Once the container is running again, you can connect to PostgreSQL using the psql command:
```
 docker exec -it my_postgres psql -U postgres
```

Important Notes

Volume Persistence: The -v pgdata:/var/lib/postgresql/data option ensures that the data is stored in a Docker volume named pgdata. This volume persists even if the container is removed.
Removing the Container: If you remove the container using docker rm my_postgres, the volume pgdata will still exist unless you explicitly remove it with:
```
  docker volume rm pgdata
```
Inspecting Volumes: You can check the existing volumes and their details using:
```
  docker volume ls
  docker volume inspect pgdata
```