Document storage driver limitations for Ubuntu and RHEL

engine/installation/linux/docker-ce/ubuntu.md

@@ -53,20 +53,34 @@ It's OK if `apt-get` reports that none of these packages are installed.
 The contents of `/var/lib/docker/`, including images, containers, volumes, and
 networks, are preserved. The Docker CE package is now called `docker-ce`.
 
-### If you need to use aufs
+### Supported storage drivers
 
-Docker CE now uses the `overlay2` storage driver by default, and it is
-recommended that you use it instead of `aufs`. If you need to use `aufs`, you
-will need to do additional preparation.
+Docker EE on Ubuntu supports `overlay2` and `aufs` storage drivers.
 
-#### Xenial 16.04 and newer
+- For new installations on version 4 and higher of the Linux kernel, `overlay2`
+  is supported and preferred over `aufs`.
+- For version 3 of the Linux kernel, `aufs` is supported because `overlay` or
+  `overlay2` drivers are not supported by that kernel version.
+
+If you need to use `aufs`, you will need to do additional preparation as
+outlined below.
+
+#### Extra steps for aufs
+
+<ul class="nav nav-tabs">
+  <li class="active"><a data-toggle="tab" data-target="#aufs_prep_xenial">Xenial 16.04 and newer</a></li>
+  <li><a data-toggle="tab" data-target="#aufs_prep_trusty">Trusty 14.04</a></li>
+</ul>
+<div class="tab-content">
+<div id="aufs_prep_xenial" class="tab-pane fade in active" markdown="1">
 
 For Ubuntu 16.04 and higher, the Linux kernel includes support for OverlayFS,
 and Docker CE will use the `overlay2` storage driver by default. If you need
 to use `aufs` instead, you need to configure it manually.
 See [aufs](/engine/userguide/storagedriver/aufs-driver.md)
 
-#### Trusty 14.04
+</div>
+<div id="aufs_prep_trusty" class="tab-pane fade" markdown="1">
 
 Unless you have a strong reason not to, install the
 `linux-image-extra-*` packages, which allow Docker to use the `aufs` storage
@@ -80,6 +94,9 @@ $ sudo apt-get install \
     linux-image-extra-virtual
 ```
 
+</div>
+</div> <!-- tab-content -->
+
 ## Install Docker CE
 
 You can install Docker CE in different ways, depending on your needs:

engine/installation/linux/docker-ee/rhel.md

@@ -30,11 +30,21 @@ Docker Community Edition (Docker CE) is not supported on {{ linux-dist-long }}.
 To install Docker EE, you need the 64-bit version of {{ linux-dist-long }}
 running on `x86_64`, `s390x` (IBM Z), or `ppc64le` (IBM Power) architectures.
 
-In addition, you must use the `overlay2` or `devicemapper` storage driver.
-**The `overlay2` storage driver is only supported on RHEL 7.2 or higher.** On
-production systems using `devicemapper`, you must use `direct-lvm` mode, which
-requires one or more dedicated block devices. Fast storage such as solid-state
-media (SSD) is recommended.
+In addition, you must use the `overlay2` or `devicemapper` storage driver. The
+`overlay2` driver is preferred for ease of configuration, if you are able to
+use it. The following limitations apply:
+
+**OverlayFS**:
+
+- The `overlay2` storage driver is only supported on RHEL 7.2 or higher.
+- If `selinux` is enabled, the `overlay2` storage driver is only supported on
+  RHEL 7.4 or higher.
+
+**Devicemapper**:
+
+- On production systems using `devicemapper`, you must use `direct-lvm` mode,
+  which requires one or more dedicated block devices. Fast storage such as
+  solid-state media (SSD) is recommended.
 
 {% capture selinux-warning %}
 > **Warning**: There is currently no support for `selinux` on IBM Z systems. If

engine/installation/linux/docker-ee/ubuntu.md

@@ -47,6 +47,11 @@ Docker EE is supported on `x86_64` (or `amd64`), `s390x` (IBM Z), and `ppc64el`
 
 Docker EE on Ubuntu supports `overlay2` and `aufs` storage drivers.
 
+- For new installations on version 4 and higher of the Linux kernel, `overlay2`
+  is supported and preferred over `aufs`.
+- For version 3 of the Linux kernel, `aufs` is supported because `overlay` or
+  `overlay2` drivers are not supported by that kernel version.
+
 ### Uninstall old versions
 
 Older versions of Docker were called `docker` or `docker-engine`. In addition,
@@ -61,11 +66,38 @@ It's OK if `apt-get` reports that none of these packages are installed.
 The contents of `/var/lib/docker/`, including images, containers, volumes, and
 networks, are preserved. The Docker EE package is now called `docker-ee`.
 
-### Extra packages for Trusty 14.04
+### Supported storage drivers
 
-Docker EE users must use the `aufs` storage driver on production systems. Install
-the `linux-image-extra-*` packages, which allow Docker EE to use the `aufs`
-storage driver.
+Docker EE on Ubuntu supports `overlay2` and `aufs` storage drivers.
+
+- For new installations on version 4 and higher of the Linux kernel, `overlay2`
+  is supported and preferred over `aufs`.
+- For version 3 of the Linux kernel, `aufs` is supported because `overlay` or
+  `overlay2` drivers are not supported by that kernel version.
+
+If you need to use `aufs`, you will need to do additional preparation as
+outlined below.
+
+#### Extra steps for aufs
+
+<ul class="nav nav-tabs">
+  <li class="active"><a data-toggle="tab" data-target="#aufs_prep_xenial">Xenial 16.04 and newer</a></li>
+  <li><a data-toggle="tab" data-target="#aufs_prep_trusty">Trusty 14.04</a></li>
+</ul>
+<div class="tab-content">
+<div id="aufs_prep_xenial" class="tab-pane fade in active" markdown="1">
+
+For Ubuntu 16.04 and higher, the Linux kernel includes support for OverlayFS,
+and Docker CE will use the `overlay2` storage driver by default. If you need
+to use `aufs` instead, you need to configure it manually.
+See [aufs](/engine/userguide/storagedriver/aufs-driver.md)
+
+</div>
+<div id="aufs_prep_trusty" class="tab-pane fade" markdown="1">
+
+Unless you have a strong reason not to, install the
+`linux-image-extra-*` packages, which allow Docker to use the `aufs` storage
+drivers.
 
 ```bash
 $ sudo apt-get update
@@ -75,6 +107,9 @@ $ sudo apt-get install \
     linux-image-extra-virtual
 ```
 
+</div>
+</div> <!-- tab-content -->
+
 ## Install Docker EE
 
 You can install Docker EE in different ways, depending on your needs: