What is the difference between the two docker compose commands

I have been trying to setup vault using docker composer file. I have three requirements,

Make sure the secrets and other configurations created are persisted after a container restart
Should be able to access the web ui of the vault
Start the vault using the production mode

I tried these two configuration segments.

  vault-server:
    image: vault:latest
    ports:
       - "8204:8200"
    environment:
       VAULT_ADDR: "http://0.0.0.0:8204"
       VAULT_DEV_ROOT_TOKEN_ID: "vault-plaintext-root-token"
    cap_add:
       - IPC_LOCK
    volumes:
       - ./vault/logs:/vault/logs
       - ./vault/file:/vault/file:rw
  vault_dev:
    hostname: vault
    container_name: vault
    image: vault:latest
    environment:
       VAULT_ADDR: "http://0.0.0.0:8205"
       VAULT_DEV_ROOT_TOKEN_ID: "vault-plaintext-root-token"
       VAULT_DEV_LISTEN_ADDRESS: "0.0.0.0:8205"
    ports:
       - "8205:8200"
    volumes:
       - ./vault/files:/vault/file:rw
    cap_add:
       - IPC_LOCK
    entrypoint: vault server -dev

My problems are;

With the vault server configuration, I could access the vault UI with the url http://localhost:8204/ui/ but the secrets created are not retained after restart
With the vault_dev configuration, (which I though would help me to start the vault in production mode when I remove the -dev command) I can't access the vault UI with the url http://localhost:8205/ui/

I really don't understand what is the difference between these two configuration segments and how to achieve step 1 and 3. For the persistence, since it says we need to add a volume, I tried mounting the file path, but still the content vanishes when the container is restarted. In some documents it says, in the dev mode you can't make it persist and have to run in prod mode. But I a, unable to figure out how modify the vault-server configuration set to make it run in prod mode.

Appreciate, if someone can help, as I have been going through several links for the past few days and kind of lost at the moment.

Solution

If you look at the Docker Hub page for the vault image it documents:

Running the Vault container with no arguments will give you a Vault server in development mode.

/vault/file [is used] for writing persistent storage data when using the file data storage plugin. By default nothing is written here (a dev server uses an in-memory data store); the file data storage backend must be enabled in Vault's configuration before the container is started.

(H/T @ChrisBecke who described this behavior in a comment; it is also in the well-commented Dockerfile.)

Later on that page is a section entitled "Running Vault in Server Mode for Development". The key point here is that you need to explicitly provide a command: vault server to cause it to not start up in dev mode.

@HansKilian's answer on port setup is also important here. Incorporating that answer's simplifications and the need to explicitly run vault server without -dev, you should get something like:

version: '3.8'  # most recent stable Compose file format
services:
  vault:
    image: vault:1.12.2
    environment:
      VAULT_LOCAL_CONFIG: >-
        {
          "storage": {
            "file": {"path": "/vault/file"}
          },
          "listener": [{
            "tcp": {
              "address": "0.0.0.0:8200",
              "tls_disable": true
             }
          }],
          "default_lease_ttl": "168h",
          "max_lease_ttl": "720h",
          "ui": true
        }
    ports:
       - "8204:8200"
    cap_add:
       - IPC_LOCK
    volumes:
       - vault_file:/vault/file:rw
volumes:
  vault_file:

The JSON block is copied from the documentation, which also notes

Disabling TLS and using the file storage backend are not recommended for production use.

The underlying Vault storage can't be usefully accessed from the host (if nothing else, it is encrypted) and I've chosen to store it in a named Docker volume instead.

Since this is not running in dev mode, you will need to go through the steps of initializing Vault, which will give you a set of critical credentials, and then you'll need to create user identities and add credentials to Vault. It sounds like you're not looking for a fully-automated setup here, so be aware that there are some manual steps involved with some "no really don't lose these keys" output.