Using Linux containers has several advantages including **security**, **replicability**, **simplicity**, and others.

/// tip

In a hurry and already know this stuff? Jump to the [`Dockerfile` below 👇](#build-a-docker-image-for-fastapi).

///

<details>
<summary>Dockerfile Preview 👀</summary>

```Dockerfile
FROM python:3.9

WORKDIR /code

That way, you can create a token with an expiration of, let's say, 1 week. And then when the user comes back the next day with the token, you know that user is still logged in to your system.

<img class="shadow" src="/img/deployment/concepts/image01.png">

---

Now that we know the difference between the terms **process** and **program**, let's continue talking about deployments.

## Running on Startup { #running-on-startup }

      /**
       * @param delay the time from now to delay execution
       * @param unit the time unit of the delay parameter
       */
      public Schedule(long delay, TimeUnit unit) {
        this.delay = delay;
        this.unit = checkNotNull(unit);
      }

      /**
       * @param delay the time from now to delay execution
       * @since 31.1 (but only since 33.4.0 in the Android flavor)

    logger.addHandler(logHandler);
    ServiceManager manager =
        new ServiceManager(Arrays.<Service>asList(new FailRunService(), new FailStartService()));
    // Due to the implementation of the two services we know that both are now failed.  So the
    // following awaitHealthy call is just to get the exception.
    manager.startAsync();
    assertThat(manager.servicesByState().get(State.FAILED)).hasSize(2);
    IllegalStateException e =

    }

    try {
      if (method == NEXT_METHOD
          && targetException == null
          && knownOrder == KnownOrder.UNKNOWN_ORDER) {
        /*
         * We already know the iterator is an Iterator<E>, and now we know that
         * we called next(), so the returned element must be of type E.
         */
        @SuppressWarnings("unchecked")
        E targetReturnValueFromNext = (E) targetReturnValue;

    tests themselves and not the code being tested that needs that access, though there's no
    obvious way to ensure that.

    We could consider arranging things so that only the tests we know need this would get
    the add-opens. Right now that doesn't seem worth the effort, though.
    -->
    <test.add.opens>
      --add-opens java.base/java.lang=ALL-UNNAMED
      --add-opens java.base/java.util=ALL-UNNAMED

    }

    try {
      if (method == NEXT_METHOD
          && targetException == null
          && knownOrder == KnownOrder.UNKNOWN_ORDER) {
        /*
         * We already know the iterator is an Iterator<E>, and now we know that
         * we called next(), so the returned element must be of type E.
         */
        @SuppressWarnings("unchecked")
        E targetReturnValueFromNext = (E) targetReturnValue;

    tests themselves and not the code being tested that needs that access, though there's no
    obvious way to ensure that.

    We could consider arranging things so that only the tests we know need this would get
    the add-opens. Right now that doesn't seem worth the effort, though.
    -->
    <test.add.opens>
      --add-opens java.base/java.lang=ALL-UNNAMED
      --add-opens java.base/java.util=ALL-UNNAMED

					entry = strings.TrimSuffix(entry, globalDirSuffixWithSlash) + slashSeparator
					dirObjects[entry] = struct{}{}
					entries[i] = entry
					continue
				}
				// Trim slash, since we don't know if this is folder or object.
				entries[i] = entries[i][:len(entry)-1]
				continue
			}
			// Do not retain the file.
			entries[i] = ""

			if contextCanceled(ctx) {
				return ctx.Err()
			}