Postgres create extension command Docker container

Question

I need to create extensions for a Postgres instance running inside of Docker - specifically postgis. I have followed other SO posts, including this one, to no avail.

Here's what I have so far...

Dockerfile

FROM postgres
COPY ext-script.sql /docker-entrypoint-initdb.d

ext-script.sql

create extension pgcrypto;
create extension postgis;

Docker run command

docker run -d -p 5432:54323 -e POSTGRES_PASSWORD=somepassword -e POSTGRES_USER=someuser -v postgres-data:/var/lib/postgresql/data --name dbcontainer dbimage

logs

docker logs dbcontainer
/usr/local/bin/docker-entrypoint.sh: running /docker-entrypoint-initdb.d/ext-script.sql
CREATE EXTENSION
2020-02-20 22:18:01.090 UTC [60] ERROR:  could not open extension control file "/usr/share/postgresql/12/extension/postgis.control": No such file or directory
2020-02-20 22:18:01.090 UTC [60] STATEMENT:  create extension postgis;
psql:/docker-entrypoint-initdb.d/ext-script.sql:2: ERROR:  could not open extension control file "/usr/share/postgresql/12/extension/postgis.control": No such file or directory

What am I missing?

UPDATE

I ended up using the postgis dockerhub image.

Everything is easy when you know how :)

# Dockerfile
FROM postgis/postgis
COPY data.sql /docker-entrypoint-initdb.d

Answer 1

PostGIS, unlike pgcrypto, isn't included in the default PostgreSQL packages, it needs to be installed from some source prior to calling create extension postgis;. There's a pretty good PostGIS docker container on docker hub here.