# 🆙 Upgrading to a Major Update

*How to Upgrade a PostgreSQL database inside a Docker Container: A Step-by-Step Guide*

## Step 1: Backup the Database

Before upgrading, it's essential to back up your database to avoid data loss.

1. **Update `compose.yaml` to Add Volumes:**

In your `compose.yaml` file, add the necessary volumes for data and backups:

```yaml
postgres:
    ...
    volumes:
        - data:/var/lib/postgresql/data
        - backup:/backup
    ...
```

2. **Shutdown All Containers Except the Database:**

Stop all your stack's containers except for the PostgreSQL container.

3. **Dump the Database into the Backup Directory:**

Run the following command to export all SQL tables into a dump file:

```bash
docker exec -it <DB_CONTAINER_NAME> pg_dumpall -U <POSTGRES_USER> > /backup/dump.sql
```

## Step 2: Clean Up the Existing Stack

1. **Stop the Database Container:**

Bring down the PostgreSQL container:

```bash
docker compose down <DB_CONTAINER_NAME>
```

2. **Delete the Existing `data` Volume:**

To prepare for the upgrade, remove the current data volume associated with PostgreSQL.

## Step 3: Upgrade PostgreSQL

1. **Update the PostgreSQL Version:**

In the `compose.yaml` file, change the PostgreSQL image to the new version.

2. **Bring Up the Updated PostgreSQL Container:**

Run the following command to start the new version:

```bash
docker compose up -d
```

## Step 4: Clear the New Data Volume

1. **Stop All Stack Containers:**

Ensure all containers are stopped to avoid any conflicts.

2. **Delete Data Files in the Volume:**

Navigate to the PostgreSQL volume and remove the data files located in `/var/lib/docker/<DB_CONTAINER_NAME>/_data`.

## Step 5: Restore the Database

1. **Start the Database Container:**

Power on the PostgreSQL container.

2. **Import the Data from Backup:**

Use the following command to restore the dumped SQL data into the new PostgreSQL container:

```bash
docker exec -it <DB_CONTAINER_NAME> psql -U <POSTGRES_USER> -d <POSTGRES_DATABASE_NAME> < /backup/dump.sql
```

## Final Step: Bring the Stack Back Online

Once the database has been restored, you can start all your other containers again.

And that's it! 🎉 You've successfully upgraded PostgreSQL in your Docker environment.

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Happy me! 🌱