ROS2官方文档
本教程为apt-get命令安装方式，官网教程有点问题，借鉴一下大佬的安装方式

1 安装ROS2

1.1 安装秘钥相关指令

• 命令

sudo apt update && sudo apt install curl gnupg2 lsb-release

• 成功

Reading package lists... Done
Building dependency tree       
Reading state information... Done
lsb-release is already the newest version (9.20170808ubuntu1).
curl is already the newest version (7.58.0-2ubuntu3.16).
The following NEW packages will be installed:
  gnupg2
0 upgraded, 1 newly installed, 0 to remove and 6 not upgraded.
Need to get 5,292 B of archives.
After this operation, 52.2 kB of additional disk space will be used.
Do you want to continue? [Y/n] Y
Get:1 http://mirrors.aliyun.com/ubuntu bionic-updates/universe amd64 gnupg2 all 2.2.4-1ubuntu1.4 [5,292 B]
Fetched 5,292 B in 0s (37.9 kB/s)  
Selecting previously unselected package gnupg2.
(Reading database ... 269610 files and directories currently installed.)
Preparing to unpack .../gnupg2_2.2.4-1ubuntu1.4_all.deb ...
Unpacking gnupg2 (2.2.4-1ubuntu1.4) ...
Setting up gnupg2 (2.2.4-1ubuntu1.4) ...
Processing triggers for man-db (2.8.3-2ubuntu0.1) ...

1.2 授权秘钥

• 命令

curl http://repo.ros2.org/repos.key | sudo apt-key add -

• 成功

  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100  1678  100  1678    0     0   2829      0 --:--:-- --:--:-- --:--:--  2824
OK

1.3 添加ROS2软件源

• 命令

sudo sh -c 'echo "deb [arch=amd64,arm64] http://packages.ros.org/ros2/ubuntu `lsb_release -cs` main" > /etc/apt/sources.list.d/ros2-latest.list'
sudo apt-get update

• 成功

Hit:1 http://mirrors.aliyun.com/ubuntu bionic InRelease
Hit:2 http://mirrors.aliyun.com/ubuntu bionic-security InRelease                             
Hit:3 http://mirrors.aliyun.com/ubuntu bionic-updates InRelease                              
Hit:4 http://mirrors.aliyun.com/ubuntu bionic-proposed InRelease                             
Get:5 http://packages.ros.org/ros2/ubuntu bionic InRelease [4,680 B]                         
Hit:6 http://mirrors.aliyun.com/ubuntu bionic-backports InRelease                            
Hit:7 https://download.docker.com/linux/ubuntu bionic InRelease                              
Get:8 http://packages.ros.org/ros2/ubuntu bionic/main amd64 Packages [686 kB]                
Ign:9 http://mirrors.tuna.tsinghua.edu.cn/ros/ubuntu bionic InRelease                        
Hit:10 http://mirrors.tuna.tsinghua.edu.cn/ros/ubuntu bionic Release
Get:12 http://packages.ros.org/ros2/ubuntu bionic/main arm64 Packages [658 kB]
Fetched 1,349 kB in 5s (288 kB/s)  
Reading package lists... Done

1.4 安装

• 命令

sudo apt install ros-dashing-desktop

• 补充：
  本次安装直接安装了大礼包，ROS提供了两种默认搭配，如下：

#桌面版 : 包含ROS, RViz, demos, tutorials [推荐]
sudo apt install ros-dashing-desktop

#基础版:（包含通讯库、消息包、命令行工具，没有GUI工具）
sudo apt install ros-dashing-ros-base

• 成功

Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following additional packages will be installed:
  cppcheck libxaw7-dev libxpm-dev pydocstyle pyflakes pyflakes3 python-funcsigs python-mock
  python-pbr python-pyflakes python3-attr python3-bs4 python3-catkin-pkg-modules
.
.
.
Setting up ros-dashing-desktop (0.7.4-1bionic.20210521.235100) ...
Processing triggers for man-db (2.8.3-2ubuntu0.1) ...
Processing triggers for libc-bin (2.27-3ubuntu1.4) ...

ROS2到这里就安装完了，安装目录为/opt/ros/dashing

2 设置环境（可选但是推荐）

• 说明：不想设置的话，就每次启动终端手动运行一下source /opt/ros/dashing/setup.bash

2.1 未安装ROS1 / 默认使用ROS2

• 命令

echo "source /opt/ros/dashing/setup.bash" >> ~/.bashrc
source ~/.bashrc

2.2 装了ROS1，每次启动终端都手动选择版本

• 把下面的脚本添加到~/.bashrc，然后执行source ~/.bashrc

#source /opt/ros/melodic/setup.bash
#source /opt/ros/dashing/setup.bash
# ROS 1.0 melodic or ROS 2.0 Dashing
echo ROS 1.0 or ROS 2.0? 1=Melodic 2=Dashing 
read ROS
if (($ROS==1));then
source /opt/ros/melodic/setup.bash
echo "Melodic"
elif (($ROS==2));then
source /opt/ros/dashing/setup.bash
echo "Dashing"
fi

3 命令行自动补全键入（可选但是推荐）

• 说明：ROS2按Tab键不会自动补全命令，如果希望有自动补全功能，需要安装一下
• 命令

sudo apt install python3-argcomplete
source /opt/ros/dashing/setup.sh

• 成功

$ sudo apt install python3-argcomplete
Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following NEW packages will be installed:
  python3-argcomplete
0 upgraded, 1 newly installed, 0 to remove and 6 not upgraded.
Need to get 26.9 kB of archives.
After this operation, 122 kB of additional disk space will be used.
Get:1 http://mirrors.aliyun.com/ubuntu bionic/universe amd64 python3-argcomplete all 1.8.1-1ubuntu1 [26.9 kB]
Fetched 26.9 kB in 0s (70.1 kB/s)              
Selecting previously unselected package python3-argcomplete.
(Reading database ... 287952 files and directories currently installed.)
Preparing to unpack .../python3-argcomplete_1.8.1-1ubuntu1_all.deb ...
Unpacking python3-argcomplete (1.8.1-1ubuntu1) ...
Setting up python3-argcomplete (1.8.1-1ubuntu1) ...
Processing triggers for man-db (2.8.3-2ubuntu0.1) ...

4 运行demo

跟ROS1一样，ROS2也提供了demo。

• 运行listener

ros2 run demo_nodes_cpp listener

• 另起终端，运行talker

ros2 run demo_nodes_cpp talker

• 补充：
  错误1：ros2: command not found
  执行一下 2 设置环境变量
• 成功
  listener终端：

$ ros2 run demo_nodes_cpp listener
[INFO] [listener]: I heard: [Hello World: 1]
[INFO] [listener]: I heard: [Hello World: 2]
[INFO] [listener]: I heard: [Hello World: 3]
[INFO] [listener]: I heard: [Hello World: 4]
[INFO] [listener]: I heard: [Hello World: 5]

talker终端：

$ ros2 run demo_nodes_cpp talker
[INFO] [talker]: Publishing: 'Hello World: 1'
[INFO] [talker]: Publishing: 'Hello World: 2'
[INFO] [talker]: Publishing: 'Hello World: 3'
[INFO] [talker]: Publishing: 'Hello World: 4'
[INFO] [talker]: Publishing: 'Hello World: 5'

5 安装ROS1 bridge（可选）

• 说明：ROS1 bridge提供了一个网桥，可以在 ROS 1 和 ROS 2 之间交换消息， 详情见官网
• 命令

sudo apt-get install ros-dashing-ros1-bridge

• demo：使用ROS1的方式运行talker，然后使用ROS2的方式运行listener

1 新开终端，启动roscore

source /opt/ros/melodic/setup.sh
roscore

2 新开终端，启动ROS1的talker

source /opt/ros/melodic/setup.sh
rosrun rospy_tutorials talker

3 新开终端，启动ROS2的listener

source /opt/ros/dashing/setup.sh
ros2 run demo_nodes_cpp listener

4 新开终端，启动ROS1 bridge

source /opt/ros/melodic/setup.sh
source /opt/ros/dashing/setup.sh
#设置默认地址，这一句可以不要
export ROS_MASTER_URI=http://localhost:11311
ros2 run ros1_bridge dynamic_bridge

6 附加RMW实现（可选）

• 说明：
  1 ROS2相比ROS1，引入了DDS，DDS是一个国际标准，使用发布/订阅机制进行消息通讯
  2 ROS2使用的默认中间件（RMW – ROS 2 middleware）是Cyclone DDS，RMW可以更换，DDS和RM官网文档
  3 如果安装了多个RMW，可以通过设置环境变量来选择不同的RMW，如：RMW_IMPLEMENTATION=rmw_connext_cpp
• 命令

sudo apt install ros-dashing-rmw-opensplice-cpp # for OpenSplice
sudo apt install ros-dashing-rmw-connext-cpp # for RTI Connext (requires license agreement)

7 安装colcon编译工具（推荐）

• 说明：ROS的编译工具经历了catkin、ament、colcon三个阶段，ROS2使用colcon，如果需要编译还是装一下
• 命令

sudo apt install python3-colcon-common-extensions

8 编译小乌龟demo

• 创建ROS2工作空间

mkdir -p ~/dev_ws/src
cd ~/dev_ws/src

• 克隆小乌龟源码

//克隆到刚刚创建的src目录下
git clone https://github.com/ros/ros_tutorials.git -b dashing-devel

• 检查依赖项，如果所有的依赖项都正确，则控制台显示如下

$ rosdep install -i --from-path src --rosdistro dashing -y
#All required rosdeps installed successfully

• 编译

$ colcon build
Starting >>> turtlesim
[Processing: turtlesim]                               
Finished <<< turtlesim [30.7s]                         

Summary: 1 package finished [30.8s]