Add info about warnings in docker info (#5048)

edge/engine/reference/commandline/info.md

@@ -8,9 +8,27 @@ Sorry, but the contents of this page are automatically generated from
 Docker's source code. If you want to suggest a change to the text that appears
 here, you'll need to find the string by searching this repo:
 
-https://github.com/docker/cli
+https://www.github.com/docker/cli
 -->
 {% if page.datafolder contains '-edge' %}
   {% include edge_only.md section="cliref" %}
 {% endif %}
 {% include cli.md datafolder=page.datafolder datafile=page.datafile %}
+
+## Warnings about kernel support
+
+If your operating system does not enable certain capabilities, you may see
+warnings such as one of the following, when you run `docker info`:
+
+```none
+WARNING: Your kernel does not support swap limit capabilities. Limitation discarded.
+```
+
+```none
+WARNING: No swap limit support
+```
+
+You can ignore these warnings unless you actually need the ability to
+[limit these resources](/engine/admin/resource_constraints.md), in which case you
+should consult your operating system's documentation for enabling them.
+[Learn more](/engine/installation/linux/linux-postinstall.md#your-kernel-does-not-support-cgroup-swap-limit-capabilities).

engine/admin/resource_constraints.md

@@ -12,6 +12,19 @@ to control how much memory, CPU, or block IO a container can use, setting runtim
 configuration flags of the `docker run` command. This section provides details
 on when you should set such limits and the possible implications of setting them.
 
+Many of these features require your kernel to support Linux capabilities. To
+check for support, you can use the
+[`docker info`](/engine/reference/commandline/info.md) command. If a capability
+is disabled in your kernel, you may see a warning at the end of the output like
+the following:
+
+```none
+WARNING: No swap limit support
+```
+
+Consult your operating system's documentation for enabling them.
+[Learn more](/engine/installation/linux/linux-postinstall.md#your-kernel-does-not-support-cgroup-swap-limit-capabilities).
+
 ## Memory
 
 ### Understand the risks of running out of memory

engine/reference/commandline/info.md

@@ -14,3 +14,21 @@ https://www.github.com/docker/cli
   {% include edge_only.md section="cliref" %}
 {% endif %}
 {% include cli.md datafolder=page.datafolder datafile=page.datafile %}
+
+## Warnings about kernel support
+
+If your operating system does not enable certain capabilities, you may see
+warnings such as one of the following, when you run `docker info`:
+
+```none
+WARNING: Your kernel does not support swap limit capabilities. Limitation discarded.
+```
+
+```none
+WARNING: No swap limit support
+```
+
+You can ignore these warnings unless you actually need the ability to
+[limit these resources](/engine/admin/resource_constraints.md), in which case you
+should consult your operating system's documentation for enabling them.
+[Learn more](/engine/installation/linux/linux-postinstall.md#your-kernel-does-not-support-cgroup-swap-limit-capabilities).