[SOLVED] Docker Compose, how to remove bind mount data?

Issue

I'm creating a PostgreSQL database with Docker Compose on Debian 11.

• Docker version 20.10.14, build a224086
• Docker Compose version v2.3.3

When I try to shutdown Docker Compose and remove all existing data, I cannot seem to get rid of bind mounted data.

docker-compose.yml

version: '3'

services:
  postgres:
    image: postgres:9.3.25
    healthcheck:
      test: [ "CMD", "pg_isready", "-q", "-d", "postgres", "-U", "root" ]
      timeout: 45s
      interval: 10s
      retries: 10
    restart: always
    environment:
      - POSTGRES_USER=root
      - POSTGRES_PASSWORD=docker
      - APP_DB_USER=app_user
      - APP_DB_PASS=docker
      - APP_DB_NAME=myapp_db
    # Notice this creates bind mounts, not volumes!
    volumes:
      - ./db-entry-point:/docker-entrypoint-initdb.d/
      - ./postgres-db-data:/var/lib/postgresql/data
    ports:
      - 5432:5432

The command below is issued to shutdown docker containers. I know it doesn't remove volumes by default. --volumes argument could be used for removing volumes, but I tested that it doesn't remove bind mound data.

docker compose -f /opt/storage/disk-03/docker/myapp-db/docker-compose.yml down

These files are on the bind mount target directory:

ls -la /opt/storage/disk-03/docker/myapp-db/postgres-db-data/
total 44
drwx------ 15 systemd-timesync root               329 Mar 29 09:52 .
drwxr-xr-x  4 root             root                78 Mar 29 09:35 ..
-rw-------  1 systemd-timesync systemd-timesync     4 Mar 28 14:52 PG_VERSION
drwx------  7 systemd-timesync systemd-timesync    67 Mar 28 14:52 base
drwx------  2 systemd-timesync systemd-timesync  4096 Mar 29 09:51 global
drwx------  2 systemd-timesync systemd-timesync    18 Mar 28 14:52 pg_clog
-rw-------  1 systemd-timesync systemd-timesync  4486 Mar 28 14:52 pg_hba.conf
-rw-------  1 systemd-timesync systemd-timesync  1636 Mar 28 14:52 pg_ident.conf
drwx------  4 systemd-timesync systemd-timesync    36 Mar 28 14:52 pg_multixact
drwx------  2 systemd-timesync systemd-timesync    18 Mar 29 09:50 pg_notify
drwx------  2 systemd-timesync systemd-timesync     6 Mar 28 14:52 pg_serial
drwx------  2 systemd-timesync systemd-timesync     6 Mar 28 14:52 pg_snapshots
drwx------  2 systemd-timesync systemd-timesync   105 Mar 29 09:52 pg_stat
drwx------  2 systemd-timesync systemd-timesync     6 Mar 29 09:52 pg_stat_tmp
drwx------  2 systemd-timesync systemd-timesync    18 Mar 28 14:52 pg_subtrans
drwx------  2 systemd-timesync systemd-timesync     6 Mar 28 14:52 pg_tblspc
drwx------  2 systemd-timesync systemd-timesync     6 Mar 28 14:52 pg_twophase
drwx------  3 systemd-timesync systemd-timesync    60 Mar 28 14:52 pg_xlog
-rw-------  1 systemd-timesync systemd-timesync 20120 Mar 28 14:52 postgresql.conf
-rw-------  1 systemd-timesync systemd-timesync    37 Mar 29 09:50 postmaster.opts

I'm not sure how to delete these files as rm -rf doesn't remove them. ls -la /opt/storage/disk-03/docker/myapp-db/postgres-db-data/ still lists the files.

sudo rm -rf /opt/storage/disk-03/docker/myapp-db/postgres-db-data/*

What would be the right way from Docker's perspective to remove these files?

Solution

Seems that the files can be removed by changing the owner of the files first and then removing. I'm not sure what's going on in the underlying OS, but I tested this couple times and it works.

# This doesn't remove the files when files are owned by "systemd-timesync"
sudo rm -rf /opt/storage/disk-03/docker/myapp-db/postgres-db-data/*

# chown to admin user
sudo chown -R admin. /opt/storage/disk-03/docker/myapp-db/postgres-db-data/
# Now removal works
sudo rm -rf /opt/storage/disk-03/docker/myapp-db/postgres-db-data/*

Answered By - Eastman

Answer Checked By - Pedro (WPSolving Volunteer)