docker_postgres_update

### upgrade your dockerized postgresql version in docker container

Background: I've wanted to upgrade the Postgresql version of one of my images from version 11 to version 14.

1. create a temp directory with some space left on the disk
```bash
mkdir $directory
```

2. create a Dockerfile with 2 postgres versions in it. Example:

```bash
FROM postgres:11-alpine3.15 AS old

FROM postgres:14-alpine3.15@sha256:a00af33e23643f497a42bc24d2f6f28cc67f3f48b076135c5626b2e07945ff9c AS new

COPY --from=old /usr/local/ /usr/local_old
```

Note: replace the images to your desired postgresql version.

3. enter the container and mount your postgres data directories:

```bash
docker run -it -v /$old_database_directory:/data_old -v /$new_database_directory/:/data_new -u 70:70 postgres_migration sh
```

4. create a new PostgreSQL database cluster in the container:

```bash
/usr/local/bin/initdb -U $database_user -D /data_new/
```

5. perform a pg_upgrade to upgrade a PostgreSQL server instance:

```bash
/usr/local/bin/pg_upgrade -U $database_user -b /usr/local_old/bin/ -B /usr/local/bin/ -d /data_old/ -D /data_new/
```

6. exit the "postgres_migration" container and start your desired postgres container with the new image and the new database directory

Note: this is the manual documentation for doing this. I've tried it with tools like: https://github.com/tianon/docker-postgres-upgrade but found my way of doing this for a smaller database way better.