ROS安装

1：检查Unbuntu的软件和更新源

2：设置Ros的下载源

2.1设置中科大源: 在终端输入如下命令后回车

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

2.2 设置公钥： 在终端输入如下命令后回车

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

2.3 更新最新可用软件包列表：在终端输入以下命令后回车

sudo apt update

3.安装ROS

在终端输入以下命令后回车

sudo apt install ros-melodic-desktop-full

4.设置环境变量

在终端输入以下命令后回车

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

5.下载其他功能组件

在终端输入以下命令后回车

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

6.rosdep init 初始化

6.1.在终端输入以下命令后回车

sudo chmod 777 /etc
sudo rosdep init

6.2.常见报错

报错:
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.

6.3.原因：初始化的这一步将会从外国的网站raw.githubusercontent.com拉取一些信息和文件。这个网站现在被墙了，导致这一步出错。

解决: 修改hosts文件

sudo gedit /etc/hosts

把下面这些地址拷贝到hosts文件末尾，然后保存。

    192.30.253.118 gist.github.com
    185.199.110.153 github.io
    151.101.113.194 github.global.ssl.fastly.net
    52.216.227.168 github-cloud.s3.amazonaws.com
    52.74.223.119 github.com
    199.232.28.133 avatars1.githubusercontent.com
    199.232.28.133 avatars2.githubusercontent.com
    199.232.28.133 avatars0.githubusercontent.com
    199.232.28.133 avatars3.githubusercontent.com
    199.232.28.133 raw.githubusercontent.com
    199.232.28.133 user-images.githubusercontent.com
    199.232.28.133 avatars.githubusercontent.com
    199.232.28.133 github.map.fastly.net
    199.232.28.133 avatars7.githubusercontent.com
    54.239.31.69 aws.amazon.com
    54.239.30.25 console.aws.amazon.com
    54.239.96.90 ap-northeast-1.console.aws.amazon.com
    54.240.226.81 ap-southeast-1.console.aws.amazon.com
    54.240.193.125 ap-southeast-2.console.aws.amazon.com
    54.239.54.102 eu-central-1.console.aws.amazon.com
    177.72.244.194 sa-east-1.console.aws.amazon.com
    176.32.114.59 eu-west-1.console.aws.amazon.com
    54.239.31.128 us-west-1.console.aws.amazon.com
    54.240.254.230 us-west-2.console.aws.amazon.com
    54.239.38.102 s3-console-us-standard.console.aws.amazon.com
    54.231.49.3 s3.amazonaws.com
    52.219.0.4 s3-ap-northeast-1.amazonaws.com
    54.231.242.170 s3-ap-southeast-1.amazonaws.com
    54.231.251.21 s3-ap-southeast-2.amazonaws.com
    54.231.193.37 s3-eu-central-1.amazonaws.com
    52.218.16.140 s3-eu-west-1.amazonaws.com
    52.92.72.2 s3-sa-east-1.amazonaws.com
    54.231.236.6 s3-us-west-1.amazonaws.com
    54.231.168.160 s3-us-west-2.amazonaws.com
    52.216.80.48 github-cloud.s3.amazonaws.com
    54.231.40.3 github-com.s3.amazonaws.com
    52.216.20.171 github-production-release-asset-2e65be.s3.amazonaws.com
    52.216.228.168 github-production-user-asset-6210df.s3.amazonaws.com

执行sudo gedit /etc/resolv.conf，将原有的nameserver这一行注释，并添加以下两行：

sudo gedit /etc/resolv.conf

nameserver 8.8.8.8 #google域名服务器
nameserver 8.8.4.4 #google域名服务器

再次执行sudo rosdep init，这次会报一个问题，就是文件已存在：

sudo rosdep init

ERROR: default sources list file already exists: /etc/ros/rosdep/sources.list.d/20-default.list
Please delete if you wish to re-initialize

这时候直接删除这个文件sudo rm /etc/ros/rosdep/sources.list.d/20-default.list，再次执行sudo rosdep init，我至今操作过很多次，没有出现不成功的状态，如果实在不成功，试试换手机热点，多执行几次，最后输出如下信息就OK了：

sudo rm /etc/ros/rosdep/sources.list.d/20-default.list

sudo rosdep init

显示如下信息，则rosdep初始化成功

    wrote /etc/ros/rosdep/sources.list.d/20-default.list
    Recommended: please run
    rosdep update

7：解决 rosdep update 问题

常见报错信息就是各种The read operation timed out.。
解决，直接从对应网址保存所有需要的文件，然后把网络路径改成本地文件路径：

链接: https://pan.baidu.com/s/1JGFlI0hYo6tVEicQXnSj7w
提取码: xiao 

下载所有的文件，整理好文件夹，对于主要的yaml文件的路径都在20-default.list这个里面有，基本套路
就是https://raw.githubusercontent.com/ros/rosdistro/master/XXX后面的xxx根据不同文件替换一下，
打开index-v4.yaml能看到所有需要的其他子文件夹，yaml文件和gz 压缩包:

1：将下载的文件夹移动到etc/ros/ros_github/为你自己提取安放的路径

直接输进浏览器地址栏，都能直接打开对应的yaml和.gz文件，ctrl+s保存即可，最后形成这么一个文件夹，文件夹的名字自己随便起都可以，里面的子文件夹一定和index-v4.yaml保持一致，如下图所示(我整理好了，大家也可以直接用)。

修改 index-v4.yaml的路径和20-default.list文件里面的路径：

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

比如我最后放那些yaml的文件夹放在/etc/ros/ros_github，将网址地址改为file:///etc/ros/ros_github/index-v4.yaml如下图所示

2：修改 /etc/ros/rosdep/sources.list.d/20-default.list文件。

sudo gedit /etc/ros/rosdep/sources.list.d/20-default.list

把里面指向网址的路径改为本地，比如我最后放那些yaml的文件夹放在/etc/ros/ros_github，

修改如下：

# os-specific listings first
yaml file:///etc/ros/ros_github/osx-homebrew.yaml osx
# generic
yaml file:///etc/ros/ros_github/base.yaml
yaml file:///etc/ros/ros_github/python.yaml
yaml file:///etc/ros/ros_github/ruby.yaml
gbpdistro file:///etc/ros/ros_github/fuerte.yaml fuerte
# newer distributions (Groovy, Hydro, ...) must not be listed anymore, they are being fetched from the rosdistro index.yaml instead

3：再次执行rosdep update命令

检查安装情况：运行小海龟和rviz

建议再执行以下环境配置命令(有的同学可能漏了，且再来一次无妨)：

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

4：再次执行

rosdep update

如过报错，则从新开一个命令框进行更新

8：创建小海龟

1.终端输入命令回车:

roscore

出现以上提示则代表安装成功。
2.检查基础功能
在终端成功输入roscore后，开启第二个终端输入

rosrun turtlesim turtlesim_node

3：会出现一个小海龟，最后开启第三个终端输入

rosrun turtlesim turtle_teleop_key 

参考：https://blog.csdn.net/sinat_25923849/article/details/107976434