How to setup volume for postgres log folder - Permission denied error - postgresql

Question

Currently, I would like to mount logging folder for postgres, so that even after host machine restart, logging information is still preserved.
I use the following docker-compose.yml
docker-compose.yml
version: '2'
services:
postgres:
image: postgres:latest
restart: always
environment:
- POSTGRES_USER=postgres
- POSTGRES_PASSWORD=55F4rGFwsXXXXXX
ports:
- "5432:5432"
volumes:
- postgres_data:/var/lib/postgresql/data
- postgres_logs:/logs
# Make Postgres log to a file.
# More on logging with Postgres: https://www.postgresql.org/docs/current/static/runtime-config-logging.html
command: postgres -c logging_collector=on -c log_destination=stderr -c log_directory=/logs
volumes:
postgres_data:
postgres_logs:
However, I'm getting the following permission denied error.
postgres_1 | 2018-02-19 09:03:45.359 UTC [1] LOG: database system is shut down
postgres_1 | 2018-02-19 09:04:45.963 UTC [1] LOG: listening on IPv4 address "0.0.0.0", port 5432
postgres_1 | 2018-02-19 09:04:45.963 UTC [1] LOG: listening on IPv6 address "::", port 5432
postgres_1 | 2018-02-19 09:04:45.965 UTC [1] LOG: listening on Unix socket "/var/run/postgresql/.s.PGSQL.5432"
postgres_1 | 2018-02-19 09:04:45.972 UTC [1] FATAL: could not open log file "/logs/postgresql-2018-02-19_090445.log": Permission denied
postgres_1 | 2018-02-19 09:04:45.974 UTC [1] LOG: database system is shut down
postgres_1 | 2018-02-19 09:05:46.741 UTC [1] LOG: listening on IPv4 address "0.0.0.0", port 5432
postgres_1 | 2018-02-19 09:05:46.741 UTC [1] LOG: listening on IPv6 address "::", port 5432
postgres_1 | 2018-02-19 09:05:46.744 UTC [1] LOG: listening on Unix socket "/var/run/postgresql/.s.PGSQL.5432"
postgres_1 | 2018-02-19 09:05:46.753 UTC [1] FATAL: could not open log file "/logs/postgresql-2018-02-19_090546.log": Permission denied
postgres_1 | 2018-02-19 09:05:46.755 UTC [1] LOG: database system is shut down
postgres_1 | 2018-02-19 09:06:47.366 UTC [1] LOG: listening on IPv4 address "0.0.0.0", port 5432
postgres_1 | 2018-02-19 09:06:47.366 UTC [1] LOG: listening on IPv6 address "::", port 5432
postgres_1 | 2018-02-19 09:06:47.368 UTC [1] LOG: listening on Unix socket "/var/run/postgresql/.s.PGSQL.5432"
postgres_1 | 2018-02-19 09:06:47.375 UTC [1] FATAL: could not open log file "/logs/postgresql-2018-02-19_090647.log": Permission denied
postgres_1 | 2018-02-19 09:06:47.377 UTC [1] LOG: database system is shut down
Anyone has idea how can I resolve such error?

Answer 1

2nd Edit
After some reading it seems that is not possible to do this the way you need. You would need to be able to define file ownership when declaring a volume with docker-compose, and this is something that is not supported by the docker engine. But there are a few workarounds that you can consider, check here for more details.
As a workaround you could create a Dockerfile extending postgres and add this:
# ...
RUN mkdir /logs
RUN chown postgres:postgres /logs
Edit
After some experimentation this is working:
version: '2'
services:
postgres:
image: postgres:latest
restart: always
environment:
- POSTGRES_USER=postgres
- POSTGRES_PASSWORD=55F4rGFwsXXXXXX
ports:
- "5432:5432"
volumes:
- postgres_data:/var/lib/postgresql/data
- ./:/logs:z
# Make Postgres log to a file.
# More on logging with Postgres: https://www.postgresql.org/docs/current/static/runtime-config-logging.html
command: postgres -c logging_collector=on -c log_destination=stderr -c log_directory=/logs
volumes:
postgres_data:
Original answer
I accidentally got it working by doing this, first running docker-compose up with this docker-compose file:
version: '2'
services:
postgres:
image: postgres:latest
restart: always
environment:
- POSTGRES_USER=postgres
- POSTGRES_PASSWORD=55F4rGFwsXXXXXX
ports:
- "5432:5432"
volumes:
- postgres_data:/var/lib/postgresql/data
- postgres_logs:/logs:z
# Make Postgres log to a file.
# More on logging with Postgres: https://www.postgresql.org/docs/current/static/runtime-config-logging.html
command: /bin/bash -c "mkdir -p /logs && chmod -R 777 /logs && postgres -c logging_collector=on -c log_destination=stderr -c log_directory=/logs"
volumes:
postgres_data:
postgres_logs:
This fails with:
postgres_1 | "root" execution of the PostgreSQL server is not
permitted. postgres_1 | The server must be started under an
unprivileged user ID to prevent postgres_1 | possible system security
compromise. See the documentation for postgres_1 | more information
on how to properly start the server.
After reverting the changes to command and running again then works, but obviously this is not a solution so stick with the edited answer above.

Answer 2

the problem is the permission in host, not in container.
so in host,
chmod -R 777 postgres_logs