Ubuntu18.04下安装ROS Melodic

参考：ROSwikihttp://wiki.ros.org/melodic/Installation/Ubuntu

1.软件与更新

Ubuntu软件开启”restricted”、”universe” 和 “multiverse”

2.设置可以从镜像源

官网

sudo sh -c 'echo "deb http://packages.ros.org/ros/ubuntu $(lsb_release -sc) main" > /etc/apt/sources.list.d/ros-latest.list'

清华源

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

中科大源

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'

3.添加秘钥

sudo apt-key adv --keyserver 'hkp://keyserver.ubuntu.com:80' --recv-key C1CF6E31E6BADE8868B172B4F42ED6FBAB17C654

4.更新软件源

sudo apt-get update

5.下载ros

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

6.初始化操作

sudo rosdep init
rosdep update

7.环境配置

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

8.安装rosinstall

sudo apt-get install python-rosinstall python-rosinstall-generator python-wstool build-essential

9.小海龟

第一个终端敲入命令：

roscore

第二个终端敲入命令：

rosrun turtlesim turtlesim_node
#小海龟出现

第三个终端敲入命令：

rosrun turtlesim turtle_teleop_key
#键盘控制海龟移动

10.ros卸载

sudo apt-get purge ros-*
sudo rm -rf /etc/ros #rosdep文件夹
sudo gedit ~/.bashrc #删除ros的环境变量

rosdep init 错误

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.

参考知乎

解决方案

证书问题
```
sudo apt-get install ca-certificates
```

ssl certs问题

sudo c_rehash /etc/ssl/certs 
sudo -E rosdep init

手动创建20-default.list文件

sudo mkdir -p /etc/ros/rosdep/sources.list.d

cd /etc/ros/rosdep/sources.list.d

sudo gedit 20-default.list #手动打开链接，粘贴文本内容。所有raw.githubusercontent.com改为raw.github.com

rosdep update

```
rosdep update报错<urlopen error <urlopen error [Errno 111] Connection refused>

解决方法：
sudo gedit /etc/resolv.conf

将原有的nameserver这一行注释，并添加以下两行：

nameserver 8.8.8.8 #google域名服务器

nameserver 8.8.4.4 #google域名服务器