主机系统： CoreOS```shelliZwz9id7ajv83ikpa2hhn2Z ~ # cat /etc/os-releaseNAME="Container Linux by CoreOS"ID=coreosVERSION=1590.0.0VERSION_ID=1590.0.0BUILD_ID=2017-11-08-0831PRETTY_NAME="Container Linux by CoreOS 1590.0.0 (Ladybug)"ANSI_COLOR="38;5;75"HOME_URL=" coreos.com/"BUG_REPORT_URL="issues.coreos.com"COREOS_BOARD="amd64-usr"
```
由于CoreOS没有包管理工具且是只读文件系统，不能方便的安装流行的Linux世界的软件，所以打算在CoreOS上在运行个CentOS7，然后在容器内部再部署一套Docker，一下是遇到的额问题的解决。
首先启动CentOS容器：`docker run -d --name=ctj --restart=always -e "container=docker" --privileged=true -p 2222:22 -p 2121:21 -v /sys/fs/cgroup:/sys/fs/cgroup -v /var/run/docker.sock:/var/run/docker.sock -v /root:/root -v /home:/home centos /usr/sbin/init`
特别解释：
- 在CentOS7下如果默认不加init启动命令的话不会启动systemd进程的，报错`docker Failed to get D-Bus connection ` ,参考资料： yhz61010.iteye.com/blog/235259…
- 进入容器后，执行下面命令：
```bashyum makecache yum install -y epel-release
sed -e 's!^mirrorlist=!#mirrorlist=!g' -e 's!^#baseurl=!baseurl=!g' -e 's!//download\.fedoraproject\.org/pub!//mirrors.ustc.edu.cn!g' -e 's!http://mirrors\.ustc!https://mirrors.ustc!g' -i /etc/yum.repos.d/epel.repo /etc/yum.repos.d/epel-testing.repo
yum makecache yum install htop
yum install kubernetes.x86_64 -y ```通过安装 kubernetes工具包会自动安装Docker，
执行： `docker version`:发现 daemon进程没启动：
```/❯❯❯ docker versionClient: Version: 1.12.6 API version: 1.24 Package version: docker-1.12.6-61.git85d7426.el7.centos.x86_64 Go version: go1.8.3 Git commit: 85d7426/1.12.6 Built: Tue Oct 24 15:40:21 2017 OS/Arch: linux/amd64Cannot connect to the Docker daemon. Is the docker daemon running on this host?
```然后执行： `dockerd` 又报以下错```INFO[0000] libcontainerd: new containerd process, pid: 624WARN[0001] 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.WARN[0001] devmapper: XFS is not supported in your system. Either the kernel doesn't support it or mkfs.xfs is not in your PATH. Defaulting to ext4 filesystemINFO[0001] devmapper: Creating filesystem ext4 on device docker-0:46-2619452-baseINFO[0001] devmapper: Error while creating filesystem ext4 on device docker-0:46-2619452-base: exec: "mkfs.ext4": exe cutable file not found in $PATHWARN[0001] devmapper: Failed to deactivatePool: Device is BusyFATA[0001] Error starting daemon: error initializing graphdriver: exec: "mkfs.ext4": executable file not found in $PA TH
```
这里有两个问题，一个是 没有安装 iptables，另一个问题是 没有 mkfs.ext4 命令，执行 `yum install -y e4fsprogs iptables.x86_64 ` 然后加载ext4模块，
`modprobe ext4` 再执行 `
dockerd` 发现能启动了
虽然有error但不影响使用，然后Ctrl^c 退出，使用 `systemctl enable docker` 允许自启动，`systemctl start docker` 启动Docker，
来个命令测试下：
现在 Docker内再启动Docker完成，开始发挥你的想象力吧! --- jyao
