Merge branch 'v2.0' into v2.1

docs/content/providers/file.md

@@ -23,17 +23,17 @@ You can write one of these mutually exclusive configuration elements:
     
     ```toml tab="File (TOML)"
     [providers.file]
-      filename = "/my/path/to/dynamic-conf.toml"
+      directory = "/path/to/dynamic/conf"
     ```
     
     ```yaml tab="File (YAML)"
     providers:
       file:
-        filename: "/my/path/to/dynamic-conf.yml"
+        directory: "/path/to/dynamic/conf"
     ```
     
     ```bash tab="CLI"
-    --providers.file.filename=/my/path/to/dynamic_conf.toml
+    --providers.file.directory=/path/to/dynamic/conf
     ```
     
     Declaring Routers, Middlewares & Services:
@@ -100,6 +100,22 @@ You can write one of these mutually exclusive configuration elements:
 
 If you're in a hurry, maybe you'd rather go through the [dynamic configuration](../reference/dynamic-configuration/file.md) references and the [static configuration](../reference/static-configuration/overview.md).
 
+!!! warning "Limitations"
+
+    With the file provider, Traefik listens for file system notifications to update the dynamic configuration.
+    
+    If you use a mounted/bound file system in your orchestrator (like docker or kubernetes), the way the files are linked may be a source of errors.
+    If the link between the file systems is broken, when a source file/directory is changed/renamed, nothing will be reported to the linked file/directory, so the file system notifications will be neither triggered nor caught. 
+    
+    For example, in docker, if the host file is renamed, the link to the mounted file will be broken and the container's file will not be updated.
+    To avoid this kind of issue, a good practice is to:
+        
+    * set the Traefik [**directory**](#directory) configuration with the parent directory
+    * mount/bind the parent directory
+
+    As it is very difficult to listen to all file system notifications, Traefik use [fsnotify](https://github.com/fsnotify/fsnotify).
+    If using a directory with a mounted directory does not fix your issue, please check your file system compatibility with fsnotify.
+    
 ### `filename`
 
 Defines the path of the configuration file.
@@ -148,19 +164,19 @@ It works with both the `filename` and the `directory` options.
 ```toml tab="File (TOML)"
 [providers]
   [providers.file]
-    filename = "dynamic_conf.toml"
+    directory = "/path/to/dynamic/conf"
     watch = true
 ```
 
 ```yaml tab="File (YAML)"
 providers:
   file:
-    filename: dynamic_conf.yml
+    directory: /path/to/dynamic/conf
     watch: true
 ```
 
 ```bash tab="CLI"
---providers.file.filename=dynamic_conf.toml
+--providers.file.directory=/my/path/to/dynamic/conf
 --providers.file.watch=true
 ```
 

docs/content/providers/kubernetes-crd.md

@@ -12,6 +12,23 @@ we ended up writing a [Custom Resource Definition](https://kubernetes.io/docs/co
 
 See the dedicated section in [routing](../routing/providers/kubernetes-crd.md).
 
+## LetsEncrypt Support with the Custom Resource Definition Provider
+
+By design, Traefik is a stateless application, meaning that it only derives its configuration from the environment it runs in, without additional configuration.
+For this reason, users can run multiple instances of Traefik at the same time to achieve HA, as is a common pattern in the kubernetes ecosystem.
+
+When using a single instance of Traefik with LetsEncrypt, no issues should be encountered, however this could be a single point of failure.
+Unfortunately, it is not possible to run multiple instances of Traefik 2.0 with LetsEncrypt enabled, because there is no way to ensure that the correct instance of Traefik will receive the challenge request, and subsequent responses.
+Previous versions of Traefik used a [KV store](https://docs.traefik.io/v1.7/configuration/acme/#storage) to attempt to achieve this, but due to sub-optimal performance was dropped as a feature in 2.0.
+
+If you require LetsEncrypt with HA in a kubernetes environment, we recommend using [TraefikEE](https://containo.us/traefikee/) where distributed LetsEncrypt is a supported feature.
+
+If you are wanting to continue to run Traefik Community Edition, LetsEncrypt HA can be achieved by using a Certificate Controller such as [Cert-Manager](https://docs.cert-manager.io/en/latest/index.html).
+When using Cert-Manager to manage certificates, it will create secrets in your namespaces that can be referenced as TLS secrets in your [ingress objects](https://kubernetes.io/docs/concepts/services-networking/ingress/#tls).
+When using the Traefik Kubernetes CRD Provider, unfortunately Cert-Manager cannot interface directly with the CRDs _yet_, but this is being worked on by our team.
+A workaround it to enable the [Kubernetes Ingress provider](./kubernetes-ingress.md) to allow Cert-Manager to create ingress objects to complete the challenges.
+Please note that this still requires manual intervention to create the certificates through Cert-Manager, but once created, Cert-Manager will keep the certificate renewed.
+
 ## Provider Configuration
 
 ### `endpoint`

docs/content/providers/kubernetes-ingress.md

@@ -47,6 +47,20 @@ spec:
               servicePort: 80
 ```
 
+## LetsEncrypt Support with the Ingress Provider
+
+By design, Traefik is a stateless application, meaning that it only derives its configuration from the environment it runs in, without additional configuration.
+For this reason, users can run multiple instances of Traefik at the same time to achieve HA, as is a common pattern in the kubernetes ecosystem.
+
+When using a single instance of Traefik with LetsEncrypt, no issues should be encountered, however this could be a single point of failure.
+Unfortunately, it is not possible to run multiple instances of Traefik 2.0 with LetsEncrypt enabled, because there is no way to ensure that the correct instance of Traefik will receive the challenge request, and subsequent responses.
+Previous versions of Traefik used a [KV store](https://docs.traefik.io/v1.7/configuration/acme/#storage) to attempt to achieve this, but due to sub-optimal performance was dropped as a feature in 2.0.
+
+If you require LetsEncrypt with HA in a kubernetes environment, we recommend using [TraefikEE](https://containo.us/traefikee/) where distributed LetsEncrypt is a supported feature.
+
+If you are wanting to continue to run Traefik Community Edition, LetsEncrypt HA can be achieved by using a Certificate Controller such as [Cert-Manager](https://docs.cert-manager.io/en/latest/index.html).
+When using Cert-Manager to manage certificates, it will create secrets in your namespaces that can be referenced as TLS secrets in your [ingress objects](https://kubernetes.io/docs/concepts/services-networking/ingress/#tls).
+
 ## Provider Configuration
 
 ### `endpoint`