Merge ~valentinviennot/ubuntu-docker-images:update-prometheus-alertmanager-readme into ~ubuntu-docker-images/ubuntu-docker-images/+git/prometheus-alertmanager:edge

[Valentin Viennot]

[Lucas Kanashiro (lucaskanashiro)]

Minor fix needed.

review: Needs Fixing

[Richard Harding (rharding)]

Just a partial review as it looks like Sergio has this, but -1 on any non-UTC timezone config if we have to have it.

review: Needs Fixing

[Lucas Kanashiro (lucaskanashiro)]

The TZ config is on our radar. I am approving this MP.

review: Approve

diff --git a/oci/README.md b/oci/README.md
index 8367dc5..3f3324a 100644
--- a/oci/README.md
+++ b/oci/README.md
@@ -6,7 +6,7 @@ The Alertmanager handles alerts sent by client applications such as the Promethe
 
 ## Tags
 
-* `0.21.0`, `0.21`, `beta` - **/!\ this is a beta release**
+* `0.21.0-focal`, `0.21.0`, `0.21-focal`, `0.21`, `focal`, `beta` - **/!\ this is a beta release**
 
 ## Architectures supported
 
@@ -17,24 +17,19 @@ The Alertmanager handles alerts sent by client applications such as the Promethe
 ### Docker CLI
 
 ```sh
-$ docker run --name alertmanager -e TZ=UTC -d squeakywheel/prometheus-alertmanager:edge
+$ docker run -d --name alertmanager -p 30093:9093 -e TZ=Europe/London squeakywheel/prometheus-alertmanager:edge
 ```
 
-Since containers are ephemeral, you may want to use persistent data rather than initializing a new database for each newly launched container.  To do this, you can use docker volumes:
-
-```sh
-$ docker run --name alertmanager -v /path/to/persisted/data:/alertmanager -e TZ=UTC -d squeakywheel/prometheus-alertmanager:edge
-```
-
-**Important note**: the directory you will be using to persist the data needs to belong to `nogroup:nobody`. You can run `chown nogroup:nobody <path_to_persist_data>` before launching your container.
+Access your Prometheus Alertmanager instance at `localhost:30093`.
 
 #### Parameters
 
 | Parameter | Description |
 |---|---|
 | `-e TZ=UTC` | Timezone. |
-| `-v /path/to/persisted/data:/alertmanager` | Pass the directory used to persist the data. |
-| `-v /path/to/alertmanager/config/file/alertmanager.yml:/etc/prometheus/alertmanger.yml` | Pass a custom config file. |
+| `-p 30093:9093` | Expose Prometheus Alertmanager server on `localhost:30093`. |
+| `-v /path/to/persisted/data:/alertmanager` | Persist data instead of initializing a new database for each newly launched container. **Important note**: the directory you will be using to persist the data needs to belong to `nogroup:nobody`. You can run `chown nogroup:nobody <path_to_persist_data>` before launching your container.|
+| `-v /path/to/alertmanager/config/file/alertmanager.yml:/etc/prometheus/alertmanger.yml` | Pass a custom config file (download this [example file](https://git.launchpad.net/~canonical-server/ubuntu-server-oci/+git/prometheus-alertmanager/plain/oci/examples/config/alertmanager.yml)). |
 
 #### Testing/Debugging
 
@@ -53,7 +48,7 @@ With microk8s running, enable the `dns` and `storage` add-ons:
 $ microk8s enable dns storage
  ```
 
-Create a configmap for the configuration file (check the upstream documentation [here](https://prometheus.io/docs/alerting/latest/configuration/)):
+Create a configmap for the configuration file (check the [Prometheus documentation](https://prometheus.io/docs/alerting/latest/configuration/)):
 
 ```sh
 $ microk8s kubectl create configmap alertmanager-config --from-file=alertmanager=config/alertmanager.yml