How to run Postgres in a docker Alpine Linux container?

I was able to do it using exec commands, so I can run postgres in a running container, in this case alpine 3.7. Note $CONTAINER_NAME is the container id from docker ps:

# Install postgresql, create user, db & start the daemon (for testing)
sudo docker exec $CONTAINER_NAME sh -c 'apk add postgresql'
sudo docker exec $CONTAINER_NAME  sh -c 'addgroup -S postgres && adduser -S postgres -G postgres'
sudo docker exec $CONTAINER_NAME sh -c 'mkdir -p /var/lib/postgresql/data'
sudo docker exec $CONTAINER_NAME sh -c 'mkdir -p /run/postgresql/'
sudo docker exec $CONTAINER_NAME sh -c 'chown -R postgres:postgres /run/postgresql/'
sudo docker exec $CONTAINER_NAME sh -c 'chmod -R 777 /var/lib/postgresql/data'
sudo docker exec $CONTAINER_NAME sh -c 'chown -R postgres:postgres /var/lib/postgresql/data'
sudo docker exec --user postgres $CONTAINER_NAME sh -c 'initdb /var/lib/postgresql/data'
sudo docker exec --user postgres $CONTAINER_NAME sh -c 'echo "host all  all    0.0.0.0/0  md5" >> /var/lib/postgresql/data/pg_hba.conf'
sudo docker exec --user postgres $CONTAINER_NAME  sh -c 'pg_ctl start -D /var/lib/postgresql/data -l /var/lib/postgresql/log.log'
sudo docker exec --user postgres $CONTAINER_NAME sh -c "psql --command \"ALTER USER postgres WITH ENCRYPTED PASSWORD 'buildpgpass';\""
sudo docker exec --user postgres $CONTAINER_NAME sh -c "psql --command \"CREATE DATABASE builddb;\""

You can also include this in your Dockerfile like so:

# Postgres
RUN apk add postgresql=11.1-r0
RUN (addgroup -S postgres && adduser -S postgres -G postgres || true)
RUN mkdir -p /var/lib/postgresql/data
RUN mkdir -p /run/postgresql/
RUN chown -R postgres:postgres /run/postgresql/
RUN chmod -R 777 /var/lib/postgresql/data
RUN chown -R postgres:postgres /var/lib/postgresql/data
RUN su - postgres -c "initdb /var/lib/postgresql/data"
RUN echo "host all  all    0.0.0.0/0  md5" >> /var/lib/postgresql/data/pg_hba.conf
RUN su - postgres -c "pg_ctl start -D /var/lib/postgresql/data -l /var/lib/postgresql/log.log && psql --command \"ALTER USER postgres WITH ENCRYPTED PASSWORD 'postgres';\" && psql --command \"CREATE DATABASE builddb;\""

This seems to work great if you want to test something out on the fly.

There are multiple problems with your dockerfile. I guess you are trying to start the server when building the image to create the main database. This won't work since each command in the dockefile will execute in its own layer, and thus when you reach RUN psql ... the database won't be started since it was started in a different layer. So you need to group the commands in one line.

Second problem is that the file /etc/init.d/postgresql does not exist. The server can be started using the postgres command:

RUN postgres &\
 psql --command "IF NOT EXISTS (SELECT FROM pg_catalog.pg_user WHERE usename = 'user')\
 THEN CREATE USER user WITH SUPERUSER ENCRYPTED PASSWORD 'password'; END IF;" &\
 createdb main

I finished with this Dockerfile:

FROM postgres:10.0-alpine

USER postgres

RUN chmod 0700 /var/lib/postgresql/data &&\
    initdb /var/lib/postgresql/data &&\
    echo "host all  all    0.0.0.0/0  md5" >> /var/lib/postgresql/data/pg_hba.conf &&\
    echo "listen_addresses='*'" >> /var/lib/postgresql/data/postgresql.conf &&\
    pg_ctl start &&\
    psql -U postgres -tc "SELECT 1 FROM pg_database WHERE datname = 'main'" | grep -q 1 || psql -U postgres -c "CREATE DATABASE main" &&\
    psql -c "ALTER USER postgres WITH ENCRYPTED PASSWORD 'mysecurepassword';"

EXPOSE 5432

This dockerfile create database 'main' (if not exists), starts postgres and sets default user password