如何在码头集装箱内安装/启动码头引擎服务

Question

我要把詹金斯从詹金斯的正式码头集装箱里拿出来。我有下面的dockerfile，按照https://docs.docker.com/engine/installation/linux/debian/的说明

FROM jenkins:2.32.1

# install docker inside this container
USER root
    # Install Docker inside Jenkins
    RUN apt-get update
    RUN apt-get purge "docker.io*"
    RUN apt-get update
    RUN apt-get install -y apt-transport-https ca-certificates gnupg2
    RUN apt-key adv \
       --keyserver hkp://ha.pool.sks-keyservers.net:80 \
       --recv-keys 58118E89F3A912897C070ADBF76221572C52609D
    RUN echo "deb https://apt.dockerproject.org/repo debian-jessie main" > /etc/apt/sources.list.d/docker.list
    RUN apt-get update
    RUN apt-cache policy docker-engine
    RUN apt-get update
    RUN apt-get install -y docker-engine
    RUN gpasswd -a jenkins docker
    USER jenkins

然后我执行以下操作：

• 从这个dockerfile生成一个图像
• 从图像中运行容器
• 以root用户的身份在容器中执行bash
• 在容器内的bash中运行sudo docker service start

我得到的是：

root@1e0f4b325d58:/# sudo service docker start
mount: permission denied
rmdir: failed to remove ‘cpu’: Read-only file system
mount: permission denied
rmdir: failed to remove ‘cpuacct’: Read-only file system
mount: permission denied
rmdir: failed to remove ‘net_cls’: Read-only file system
mount: permission denied
rmdir: failed to remove ‘net_prio’: Read-only file system
/etc/init.d/docker: 96: ulimit: error setting limit (Operation not permitted)

Answer 1

如果要在码头内运行码头，则需要将容器作为特权容器运行。

因此，像这样的东西 (1)是必需的：

docker run --privileged your_image:tag

您还需要小心iptables和Armour，但是经过一些改进之后，这是可行的。

另一种方法是允许访问容器就像这样 (2)中的停靠守护进程：

docker run -v /var/run/docker.sock:/var/run/docker.sock your_image:tag

参考：

1 https://blog.docker.com/2013/09/docker-can-now-run-within-docker/

2 https://jpetazzo.github.io/2015/09/03/do-not-use-docker-in-docker-for-ci/