Failed to start docker.service: Unit not found.
环境： Centos 7 Docker版本：docker-ce.x86_64 0:18.03.0.ce-1.el7.centos
运行命令：yum install -y kubernetes
错误：Error: docker-ce conflicts with 2:docker-1.13.1-53.git774336d.el7.centos.x86_64
错误原因：（https://stackoverflow.com/questions/44891775/kubernetes-installation-on-centos7）
According to the documentation, Kubernetes is not yet compatible with docker-ce (docker >=17.x)
On each of your machines, install Docker. Version 1.12 is recommended, but v1.10 and v1.11 are known to work as well. Versions 1.13 and 17.03+ have not yet been tested and verified by the Kubernetes node team.
解决方法：卸载docker-ce
1、查看安装过的docker：yum list installed | grep docker
2、卸载docker：yum remove -y docker-ce.x86_64 0:18.03.0.ce-1.el7.centos
3、删除容器镜像：rm -rf /var/lib/docker
再次安装kubernetes，安装成功，而且会自动安装docker
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作者：huygft
来源：CSDN
原文：https://blog.csdn.net/linkvivi/article/details/80175567
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