主机系统： CoreOS
iZwz9id7ajv83ikpa2hhn2Z ~ # cat /etc/os-release
NAME="Container Linux by CoreOS"
ID=coreos
VERSION=1590.0.0
VERSION_ID=1590.0.0
BUILD_ID=2017-11-08-0831
PRETTY_NAME="Container Linux by CoreOS 1590.0.0 (Ladybug)"
ANSI_COLOR="38;5;75"
HOME_URL="https://coreos.com/"
BUG_REPORT_URL="https://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：
yum 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 version
Client:
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/amd64
Cannot 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: 624
WARN[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 filesystem
INFO[0001] devmapper: Creating filesystem ext4 on device docker-0:46-2619452-base
INFO[0001] devmapper: Error while creating filesystem ext4 on device docker-0:46-2619452-base: exec: "mkfs.ext4": exe cutable file not found in $PATH
WARN[0001] devmapper: Failed to deactivatePool: Device is Busy
FATA[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!
