Relates to giving all Docker volumes a name.  This is an optional personal preference.  I believe OpenProject's anonymous volumes can get blown away without any impact.  So this modification is not necessary.  Also, I have only used OpenProject for a month now, so this post may contain incorrect assumptions.

I spooled-up/spooled-down the native DockerCompose script multiple times.  I converted the anonymous volumes into named volumes until I could spool-up without seeing an anonymous volume.

• Volumes with potential data to backup are named "DataVolume".
• Temp/disposable volumes are named "TempVolume".

About the volume "AssetData" (aka "opdata").  This volume is shown above with an orange "unused" tag:

• Using the native DockerCompose script will save screenshots/attachments into the "opdata" volume.
• However, using the modified script below will NOT save screenshots/attachments into AssetData (aka "opdata").  Instead, screenshots/attachments get saved into the "XXX_Web_02" volume.  I would like to know why this is.  I had to do a migration to a brand new machine and all of the screenshots/attachments migrated over fine.   Not saying this is 100% safe but it has worked so far.

Note: I only tested creating work packages.  I did not test using GIT/SVN, or any other feature.  So I would backup all volumes to be safe (including the volumes named "TempVolume").

#2020-12-19 OpenProject version 11.1
#Docker compose file modified from: https://github.com/opf/openproject-deploy/blob/stable/11/compose/docker-compose.yml
#My edits are noted with "★". Basically, I went through every anonymous volume that OpenProject created and gave it a name.  
#Initial username/password is admin/admin.
version: "3.7"

networks:
  frontend:
  backend:

x-op-restart-policy: &restart_policy
  restart: unless-stopped
x-op-image: &image
  image: openproject/community:11.1 #Have to define exact version.  Using ":latest" returns error about manifest. ★
x-op-app: &app
  <<: *image
  <<: *restart_policy
  environment:
    RAILS_CACHE_STORE: "memcache"
    OPENPROJECT_CACHE__MEMCACHE__SERVER: "cache:11211"
    OPENPROJECT_RAILS__RELATIVE__URL__ROOT: "${OPENPROJECT_RAILS__RELATIVE__URL__ROOT:-}"
    DATABASE_URL: "postgres://postgres:p4ssw0rd@db/openproject"
    USE_PUMA: "true"
    # set to true to enable the email receiving feature. See ./docker/cron for more options
    IMAP_ENABLED: "${IMAP_ENABLED:-false}"
  #See volume notes at bottom.  ★
  volumes:
    - OpenProject_DataVolume_AssetData:/var/openproject/assets

services:
  db:
    image: postgres:10
    <<: *restart_policy
    stop_grace_period: "3s"
    #See notes in "top level key" section at bottom.  ★
    volumes:
      - OpenProject_DataVolume_PostgreSqlData:/var/lib/postgresql/data
    environment:
      POSTGRES_PASSWORD: p4ssw0rd
      POSTGRES_DB: openproject
    networks:
      - backend

  cache:
    image: memcached
    <<: *restart_policy
    networks:
      - backend
    #No volume needed. I tested. ★ 

  proxy:
    <<: *image
    <<: *restart_policy
    command: "./docker/prod/proxy"
    ports:
      - "${PORT:-8080}:80"
    environment:
      APP_HOST: web
      OPENPROJECT_RAILS__RELATIVE__URL__ROOT: "${OPENPROJECT_RAILS__RELATIVE__URL__ROOT:-}"
    depends_on:
      - web
    networks:
      - frontend
    #See volume notes at bottom.  ★
    volumes:
      - OpenProject_TempVolume_Proxy_01:/var/openproject/pgdata
      - OpenProject_TempVolume_Proxy_02:/var/openproject/assets

  web:
    <<: *app
    command: "./docker/prod/web"
    networks:
      - frontend
      - backend
    depends_on:
      - db
      - cache
      - seeder
    #See volume notes at bottom.  ★
    volumes:
      - OpenProject_DataVolume_Web_01:/var/openproject/pgdata  
      - OpenProject_DataVolume_Web_02:/var/openproject/assets

  worker:
    <<: *app
    command: "./docker/prod/worker"
    networks:
      - backend
    depends_on:
      - db
      - cache
      - seeder
    #See volume notes at bottom.  ★
    volumes:
      - OpenProject_TempVolume_Worker_01:/var/openproject/pgdata
      - OpenProject_TempVolume_Worker_02:/var/openproject/assets


  cron:
    <<: *app
    command: "./docker/prod/cron"
    networks:
      - backend
    depends_on:
      - db
      - cache
      - seeder
    #See volume notes at bottom.  ★
    volumes:
      - OpenProject_TempVolume_CronJob_01:/var/openproject/pgdata  
      - OpenProject_TempVolume_CronJob_02:/var/openproject/assets
      

  seeder:
    <<: *app
    command: "./docker/prod/seeder"
    restart: on-failure
    networks:
      - backend
    #See volume notes at bottom.  ★
    volumes:
      - OpenProject_TempVolume_Seeder_01:/var/openproject/pgdata    
      - OpenProject_TempVolume_Seeder_02:/var/openproject/assets
      
      


volumes:
    #---------------------------------
    #ABOUT VOLUMES: 
    #2020-12-19 Results from test with OpenProject 11.1.  Created 50 tasks with file attachments and screenshots. Note: This is not a complete test.  Ex: I did NOT test the GIT/SVN capabilities etc.  I would backup all volumes to be safe.  
    #I named all volumes to prevent Docker from assigning a bogus anonymous GUID name.   
    #---------------------------------
    #- AssetData:         Empty.  When "opdata" is renamed, then screenshots/attachments get saved to Web_02 volume below. So this AssetData volume remains empty.  I would like to understand why this is.  But anyhow, this works.   
    #- PostgreSqlData:    ☆☆☆ Had data.  
    #- Web_01:            Empty
    #- Web_02:            ☆☆☆ Had task attachments/screenshot files.  
    #- CronJob_01:        Empty
    #- CronJob_02:        Empty
    #- Proxy_01:          Empty
    #- Proxy_02:          Empty
    #- Seeder_01:         Empty
    #- Seeder_02:         Empty
    #- Worker_01:         Empty
    #- Worker_02:         Empty
 
  OpenProject_DataVolume_AssetData:
    name: OpenProject_DataVolume_AssetData #Original volume name "opdata". ★

  OpenProject_DataVolume_PostgreSqlData:
    name: OpenProject_DataVolume_PostgreSqlData #Original volume name "pgdata".  ★

  OpenProject_DataVolume_Web_01:
    name: OpenProject_DataVolume_Web_01 #Original script had no volume name.  I gave it this name.  ★
       
  OpenProject_DataVolume_Web_02:
    name: OpenProject_DataVolume_Web_02 #Original script had no volume name.  I gave it this name.  ★
    
  OpenProject_TempVolume_Proxy_01:
    name: OpenProject_TempVolume_Proxy_01 #Original script had no volume name.  I gave it this name.  ★
    
  OpenProject_TempVolume_Proxy_02:
    name: OpenProject_TempVolume_Proxy_02 #Original script had no volume name.  I gave it this name.  ★ 

  OpenProject_TempVolume_Worker_01:
    name: OpenProject_TempVolume_Worker_01 #Original script had no volume name.  I gave it this name.  ★

  OpenProject_TempVolume_Worker_02:
    name: OpenProject_TempVolume_Worker_02 #Original script had no volume name.  I gave it this name.  ★
    
  OpenProject_TempVolume_CronJob_01:
    name: OpenProject_TempVolume_CronJob_01 #Original script had no volume name.  I gave it this name.  ★
    
  OpenProject_TempVolume_CronJob_02:
    name: OpenProject_TempVolume_CronJob_02 #Original script had no volume name.  I gave it this name.  ★
    
  OpenProject_TempVolume_Seeder_01:
    name: OpenProject_TempVolume_Seeder_01 #Original script had no volume name.  I gave it this name.  ★ 
    
  OpenProject_TempVolume_Seeder_02:
    name: OpenProject_TempVolume_Seeder_02 #Original script had no volume name.  I gave it this name.  ★