Update the manuals of docker and dockerd

Signed-off-by: yuexiao-wang <wang.yuexiao@zte.com.cn>

man/docker.1.md

@@ -7,12 +7,10 @@ docker \- Docker image and container command line interface
 # SYNOPSIS
 **docker** [OPTIONS] COMMAND [ARG...]
 
-**docker** daemon [--help|...]
-
 **docker** [--help|-v|--version]
 
 # DESCRIPTION
-is a client for interacting with the daemon (see **dockerd(8)**) through the CLI.
+**docker** is a client for interacting with the daemon (see **dockerd(8)**) through the CLI.
 
 The Docker CLI has over 30 commands. The commands are listed below and each has
 its own man page which explain usage and arguments.
@@ -62,17 +60,7 @@ unix://[/path/to/socket] to use.
 
 Use "docker help" or "docker --help" to get an overview of available commands.
 
-# RUNTIME EXECUTION OPTIONS
-
-Use the **--exec-opt** flags to specify options to the execution driver.
-The following options are available:
-
-#### native.cgroupdriver
-Specifies the management of the container's `cgroups`. You can specify `cgroupfs`
-or `systemd`. If you specify `systemd` and it is not available, the system errors
-out.
-
-#### Client
+# EXAMPLES
 For specific client examples please see the man page for the specific Docker
 command. For example:
 

man/dockerd.8.md

@@ -672,6 +672,24 @@ For information about how to create an authorization plugin, see [authorization
 plugin](https://docs.docker.com/engine/extend/authorization/) section in the
 Docker extend section of this documentation.
 
+# RUNTIME EXECUTION OPTIONS
+
+You can configure the runtime using options specified with the `--exec-opt` flag.
+All the flag's options have the `native` prefix. A single `native.cgroupdriver`
+option is available.
+
+The `native.cgroupdriver` option specifies the management of the container's
+cgroups. You can only specify `cgroupfs` or `systemd`. If you specify
+`systemd` and it is not available, the system errors out. If you omit the
+`native.cgroupdriver` option,` cgroupfs` is used.
+
+This example sets the `cgroupdriver` to `systemd`:
+
+```bash
+$ sudo dockerd --exec-opt native.cgroupdriver=systemd
+```
+
+Setting this option applies to all containers the daemon launches.
 
 # HISTORY
 Sept 2015, Originally compiled by Shishir Mahajan <shishir.mahajan@redhat.com>