ubuntu18.04 ROS melodic完整版教程及错误处理（附带 catkin_ws工作空间搭建）

一、配置Ubuntu软件库

桌面点击Ubuntu软件，接着左上角点击Ubuntu软件，点击软件和更新。
将可从互联网下载的所有选项选中，并且将下载自 选为 中国 的服务器

二、安装过程及错误处理

ros官网安装教程: ROS Instal

1. 设置安装源，与官网教程不同，此处需要设置代理源，如清华源

sudo sh -c '. /etc/lsb-release && echo "deb http://mirrors.ustc.edu.cn/ros/ubuntu/ $DISTRIB_CODENAME main" > /etc/apt/sources.list.d/ros-latest.list'

2. 设置密钥

sudo apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv-key 421C365BD9FF1F717815A3895523BAEEB01FA116

3. 更新软件包

sudo apt update

4. 安装ROS melodic
   提前安装python-rosdep，避免出现sudo rosdep：找不到命令提示

sudo apt install python-rosdep
sudo apt-get install ros-melodic-desktop-full

• 如果出现如下错误

W: GPG 错误：http://mirrors.ustc.edu.cn/ros/ubuntu bionic InRelease: 由于没有公钥，无法验证下列签名： NO_PUBKEY F42ED6FBAB17C654

• 执行以下命令

sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys F42ED6FBAB17C654

5. 初始化ROS（网络报错问题最终解决方案）
   初始化ROS过程中需要通过网络下载一些文件，但由于网络网速不够或其他原因，会出现无法下载和无法连接的错误，如下：

ERROR: cannot download default sources list from:
https://raw.githubusercontent.com/ros/rosdistro/master/rosdep/sources.list.d/20-default.list
Website may be down.

ERROR: error loading sources list:
	('The read operation timed out',)

sudo rosdep init与rosdep update 报错终极解决方案如下：

1 将rosdistro clone到本地
这里，可以选择github方式

git clone https://github.com/ros/rosdistro.git

建议选择gitee的方式（此方法下载更快，库是我自己导入的，可以使用！）

git clone https://gitee.com/huang_hongzhi/rosdistro.git

注意这里克隆的地址选择根目录，我的用户名是hhz，那么这个文件夹的地址就是～/rosdistro，即/home/hhz/rosdistro

2 创建20-default.list，对应sudo rosdep init 这一步
打开一个新终端，输入以下内容，用途是创建20-default.list

sudo su //输入你的密码切换至root
sudo mkdir -p /etc/ros/rosdep/sources.list.d   
cd /etc/ros/rosdep/sources.list.d
sudo gedit 20-default.list

将以下内容复制进20-default.list
注意：以下的yourname全部改为你们自己的用户名

#os-specific listings first
yaml file:///home/yourname/rosdistro/rosdep/osx-homebrew.yaml osx
#generic
yaml file:///home/yourname/rosdistro/rosdep/base.yaml
yaml file:///home/yourname/rosdistro/rosdep/python.yaml
yaml file:///home/yourname/rosdistro/rosdep/ruby.yaml
gbpdistro file:///home/yourname/rosdistro/releases/fuerte.yaml fuerte

#newer distributions (Groovy, Hydro, ...) must not be listed anymore, they are being fetched from the rosdistro index.yaml instead

3 替换下载网址为本地的文件

• 打开第一个文件

cd /home/yourname/rosdistro/rosdep/sources.list.d/
sudo gedit 20-default.list 

将里面所有的 raw.githubusercontent.com替换成file:///home/yourname/rosdistro的地址，如下：

# os-specific listings first
yaml file:///home/yourname/rosdistro/rosdep/osx-homebrew.yaml osx

# generic
yaml file:///home/yourname/rosdistro/rosdep/base.yaml
yaml file:///home/yourname/rosdistro/rosdep/python.yaml
yaml file:///home/yourname/rosdistro/rosdep/ruby.yaml
gbpdistro file:///home/yourname/rosdistro/releases/fuerte.yaml fuerte

# newer distributions (Groovy, Hydro, ...) must not be listed anymore, they are being fetched from the rosdistro index.yaml instead

• 打开第二个文件

cd /usr/lib/python2.7/dist-packages/rosdep2/
sudo gedit gbpdistro_support.py

替换对应的内容（注意两行都要换）

FUERTE_GBPDISTRO_URL = 'file:///home/yourname/rosdistro/' \
    'releases/fuerte.yaml'

• 打开第三个文件

cd /usr/lib/python2.7/dist-packages/rosdep2/
sudo gedit rep3.py

替换对应的内容

REP3_TARGETS_URL = 'file:///home/yourname/rosdistro/releases/targets.yaml'

• 打开第四个文件
  我电脑里是 __init__.py，但是作者的是init.py

cd /usr/lib/python2.7/dist-packages/rosdistro/
sudo gedit __init__.py

替换对应的内容

DEFAULT_INDEX_URL = 'file:///home/yourname/rosdistro/index-v4.yaml'

4 执行rosdep update
新建一个终端执行rosdep update，出现如下代码则成功：

reading in sources list data from /etc/ros/rosdep/sources.list.d
Hit file:///home/hhz/rosdistro/rosdep/osx-homebrew.yaml
Hit file:///home/hhz/rosdistro/rosdep/base.yaml
Hit file:///home/hhz/rosdistro/rosdep/python.yaml
Hit file:///home/hhz/rosdistro/rosdep/ruby.yaml
Hit file:///home/hhz/rosdistro/releases/fuerte.yaml
Query rosdistro index file:///home/hhz/rosdistro/index-v4.yaml
Skip end-of-life distro "ardent"
Add distro "bouncy"
Add distro "crystal"
Add distro "dashing"
Add distro "eloquent"
Skip end-of-life distro "groovy"
Skip end-of-life distro "hydro"
Skip end-of-life distro "indigo"
Skip end-of-life distro "jade"
Add distro "kinetic"
Skip end-of-life distro "lunar"
Add distro "melodic"
updated cache in /home/hhz/.ros/rosdep/sources.cache

ROS环境变量设置

echo "source /opt/ros/melodic/setup.bash" >> ~/.bashrc
source ~/.bashrc
sudo apt install python-rosinstall python-rosinstall-generator python-wstool build-essential

创建工作空间

初始化工作空间

mkdir -p ~/catkin_ws/src
cd ~/catkin_ws/src
catkin_init_workspace

编译工作空间

cd ~/catkin_ws/
catkin_make

使得工作空间的环境变量生效

source devel/setup.bash

使得环境变量在所有的终端中都有效

echo "source ~/catkin_ws/devel/setup.bash" >> ~/.bashrc

检查环境变量已经生效，创建一个新终端，输入：

echo $ROS_PACKAGE_PATH

如果打印的路径中包含当前工作空间的路径，则环境变量设置成功

如果以上内容对你有帮助的话，麻烦点个关注谢谢啦～