czwei：docker.service启动报错的一次排查

执行以下命令报错

systemctl restart docker

查看错误信息

systemctl status docker -l

报错信息如下：

● docker.service - Docker Application Container Engine Loaded: loaded (/usr/lib/systemd/system/docker.service; disabled; vendor preset: disabled) Drop-In: /etc/systemd/system/docker.service.d └─kolla.conf Active: failed (Result: exit-code) since 三 2018-08-01 16:32:27 CST; 52min ago Docs: https://docs.docker.com Process: 3833722 ExecStart=/usr/bin/docker daemon --insecure-registry 172.16.59.153 (code=exited, status=1/FAILURE) Main PID: 3833722 (code=exited, status=1/FAILURE) Memory: 8.0K CGroup: /system.slice/docker.service8月 01 16:32:26 czwei004 systemd[1]: Starting Docker Application Container Engine...8月 01 16:32:26 czwei004 docker[3833722]: time="2018-08-01T16:32:26.527063936+08:00" level=info msg="libcontainerd: new containerd process, pid: 3833733"8月 01 16:32:27 czwei004 docker[3833722]: time="2018-08-01T16:32:27.532317497+08:00" level=warning msg="devmapper: Usage of loopback devices is strongly discouraged for production use. Please use `--storage-opt dm.thinpooldev` or use `man docker` to refer to dm.thinpooldev section."8月 01 16:32:27 czwei004 docker[3833722]: time="2018-08-01T16:32:27.560010414+08:00" level=warning msg="devmapper: Base device already exists and has filesystem xfs on it. User specified filesystem will be ignored."8月 01 16:32:27 czwei004 docker[3833722]: time="2018-08-01T16:32:27.577758251+08:00" level=fatal msg="Error starting daemon: error initializing graphdriver: \"/var/lib/docker\" contains several valid graphdrivers: devicemapper, overlay2; Please cleanup or explicitly choose storage driver (-s <DRIVER>)"8月 01 16:32:27 czwei004 systemd[1]: docker.service: main process exited, code=exited, status=1/FAILURE8月 01 16:32:27 czwei004 systemd[1]: Failed to start Docker Application Container Engine.8月 01 16:32:27 czwei004 systemd[1]: Unit docker.service entered failed state.8月 01 16:32:27 czwei004 systemd[1]: docker.service failed.

注意到以上错误信息中

msg="Error starting daemon: error initializing graphdriver: \"/var/lib/docker\" contains several valid graphdrivers: devicemapper, overlay2; Please cleanup or explicitly choose storage driver (-s <DRIVER>)"

到docker目录下查看，有devicemapper的目录和overlay2的目录
原因是我之前装了高版本的docker-engine，默认的存储驱动是overlay2，卸载的时候docker目录下残留了overlay2的文件夹，后来安装了低版本的docker，默认的又是devicemapper，于是就有了多个存储驱动

重启机器后删除overlay2的目录后可以启动