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[work complete]How to manage Linux containers with Docker on Ubuntu
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How to manage Linux containers with Docker on Ubuntu
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================================================================================
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While full hardware virtualization such as KVM, Xen or Hyper-V is great at running fully isolated instances of multiple operating systems on a physical host, it comes with various overheads in terms of performance, resource, and provisioning time. Depending on your use cases, full machine virtuailization may actually not be necessary.
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An alternative lightweight virtualization approach is so-called [Linux Containers][1] (LXC), which provides operating system level virtualization. Without the overhead of running virtual machines, LXC allows you to run multiple instances of full Linux operating system within lightweight container sandbox. Containers can be very useful when you set up a reproducible development/test environment or deploy applications within secure sandboxes.
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[Docker][2] is an open-source tool which was developed to facilitate the deployment of Linux containers. Docker is fast becoming a de-facto standard for container technologies, being embraced in major Linux distros such as [Ubuntu][3] and [Red Hat][4].
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In this tutorial, I am going to demonstrate how to manage Linux containers with Docker on Ubuntu 14.04. Note that instructions may be slightly different for earlier versions of Ubuntu.
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At this time, the Docker package available on Ubuntu only supports 64-bit systems. To run it on 32-bit machine, you will need to [build 32-bit version of Docker from source][5].
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### Install Docker ###
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Installing Docker is easy with apt-get command.
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$ sudo apt-get install docker.io
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To allow non-root user to run Docker, add yourself to docker group. The command below will allow the current user to run Docker without root permission.
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$ sudo usermod -a -G docker $USER
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Log out and then re-login to activate group membership change.
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Next, edit the Docker configuration file to update the location of the Docker binary.
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$ sudo vi /etc/default/docker.io
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> DOCKER="/usr/bin/docker.io"
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Restart Docker service.
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$ sudo service docker.io restart
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### Manage Docker Containers ###
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If you want to start a new Docker container of Ubuntu operating system, first pull [Ubuntu][6] Docker image first. The command below will download Docker image over a network.
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$ docker pull ubuntu
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You can start a Ubuntu Docker in an interactive mode as follows. The last argument "/bin/bash" is the command that will be executed inside a container once it is launched, in this case, a simple bash shell.
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$ docker run -i -t ubuntu /bin/bash
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The above command will launch a Ubuntu container immediately (which is the beauty of containers!), and give you a shell prompt inside the container. At this point, you should be able to access a full Ubuntu operating system inside a sandboxed environment.
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To exit a Docker container, type "exit" at the prompt inside the container.
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You can launch containers in different flavors. For example, to start a Fedora container:
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$ docker.io run -i -t fedora /bin/bash
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If a Fedora Docker image is not available locally, the command will automatically download the image first, and then launch a Docker.
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If you want to launch a container with a particular distro release, you can also do that. For example, to start a Ubuntu 13.04 Docker:
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$ docker.io run -i -t ubuntu:13.04 /bin/bash
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### Container Networking ###
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Docker uses Linux bridge to interconnect containers with each other, and to connect them to external networks. After installing Docker, you should see docker0 Linux bridge created automatically by default. Every container you create will be connected to docker0 bridge interface.
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#### Custom Linux Bridge ####
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If you want, you can use a custom Linux bridge to interconnect containers. For that, you can create a custom bridge and configure it as follows. You can assign a separate subnet to the bridge, and have Dockers assigned IP addresses from the subnet. I am going to use 10.0.0.0/24 as a Docker subnet.
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$ sudo apt-get install bridge-utils
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$ sudo brctl addbr br0
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$ sudo ifconfig br0 10.0.0.1 netmask 255.255.255.0
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To make the custom bridge used by Docker, add "-b=br0" to DOCKER_OPTS variable in /etc/default/docker.io, and restart Docker service.
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$ sudo service docker.io restart
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At this point, any new container will be connected to br0, and its IP address will automatically be assigned from 10.0.0.0/24.
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#### Other Customizations ####
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There are several other ways to customize the default network settings of Docker, mostly by tweaking DOCKER_OPTS variable in /etc/default/docker.io.
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- "-dns 8.8.8.8 -dns 8.8.4.4": specify the DNS servers used by a container.
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- "-icc=false": make containers isolated from each other.
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### Troubleshooting ###
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1. You encounter the following error when running docker.io command.
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> dial unix /var/run/docker.sock: no such file or directory
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The error may be because Docker daemon is not running. Check the status of Docker daemon, and make sure to start it first.
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$ sudo service docker.io status
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$ sudo service docker.io start
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--------------------------------------------------------------------------------
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via: http://xmodulo.com/2014/05/manage-linux-containers-docker-ubuntu.html
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译者：[译者ID](https://github.com/译者ID) 校对：[校对者ID](https://github.com/校对者ID)
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本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创翻译，[Linux中国](http://linux.cn/) 荣誉推出
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[1]:https://linuxcontainers.org/
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[2]:https://www.docker.io/
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[3]:http://blog.docker.io/2014/04/docker-in-ubuntu-ubuntu-in-docker/
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[4]:http://www.redhat.com/about/news/press-archive/2014/4/red-hat-docker-expand-collaboration
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[5]:http://mwhiteley.com/linux-containers/2013/08/31/docker-on-i386.html
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[6]:http://xmodulo.com/go/ubuntubook
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在 Ubuntu 中用 Docker 管理 Linux Container 容器
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================================================================================
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当前，完全硬件虚拟化技术（KVM、Xen、Hyper-V 等）能在一个物理主机上很好地运行多个互相独立的操作系统，但这也带来一些问题：性能不佳，资源浪费，系统反应迟缓等。有时候对用户来说，完全的硬件虚拟化并不是最好的选择。
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一种替代方案是使用轻量级虚拟化技术 —— 所谓的 [Linux Container 容器][1] (LXC)，它提供的是系统级虚拟化。与跑虚拟机相比，LXC 可以在一个轻量级沙箱容器里面跑多个 Linux 操作系统。当你需要设置一些易于克隆的开发环境、测试环境，或想在安全沙盒里安装应用时，LXC 就非常有用了。
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[Docker][2] 是一个开源工具，可以让用户方便地布署 Linux Container 容器。Docker 很快变成了 container 技术的非官方标准，从而被 [Ubuntu][3] 和 [Red Hat][4]等众多发行版吸收进去。
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本教程中我会向你们演示如何在 Ubuntu 14.04 中使用 Docker 来管理 LXC。需要注意的是，本教程的一些内容可能会与其他 Ubuntu 版本下的操作会稍微有些出入。
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当前Ubuntu 系统下的 Docker 的安装包只提供64位。如果你想运行32位的 Docker，你需要[使用源码编译32位 Docker 工具][5]。
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### 安装 Docker ###
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通过 apt-get 安装 Docker 简直是小菜一碟。
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$ sudo apt-get install docker.io
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如果你不是 root 组的用户，你可以把自己加入到 docker 用户组。下面的命令可以让没有 root 权限的用户使用 Docker：
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$ sudo usermod -a -G docker $USER
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重新登录，以便让你的用户组权限生效。
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下一步是编辑 Docker 配置文件，确定 Docker 可执行文件的路径：
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$ sudo vi /etc/default/docker.io
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> DOCKER="/usr/bin/docker.io"
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重启 Docker 服务：
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$ sudo service docker.io restart
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### 管理 Docker Container 容器 ###
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如果你想在新的 Docker 容器下创建一个新的 Ubuntu 操作系统，你首先需要 pull 一个 [Ubuntu][6] 的 Docker 镜像。下面的命令可以通过网络下载 Docker 镜像：
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$ docker pull ubuntu
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你可以使用下面的命令启动 Docker 里面的 Ubuntu 系统。最后的参数“/bin/bash”表示一旦容器启动，首先会执行简单的 bash。
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$ docker run -i -t ubuntu /bin/bash
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上面的命令会立即启动 Ubuntu container 容器（这是一个完美的容器！），然后它会提供一个 shell 提示符运行环境给你。现在开始你可以通过这个沙箱环境访问一个完整的 Ubuntu 系统了。
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输入“exit”命令退出 Docker 容器。
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你也可以用下面的命令进入不同的系统。比如 Fedora：
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$ docker.io run -i -t fedora /bin/bash
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如果系统中还不存在 Fedora Docker 镜像，这个命令会自动下载它，然后启动这个 Fedora 的 Docker 容器。
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如果你想要开启指定版本的系统，比如 Ubuntu 13.04，你可以使用下面的命令：
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$ docker.io run -i -t ubuntu:13.04 /bin/bash
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### Container 容器网络设置 ###
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Docker 使用 Linux 桥接技术与其他容器通信，以及连通外网。安装完 Docker 后你应该可以看到 docker0 这个网桥，这是 Docker 默认创建的。你创建的每个容器都会通过这个网桥连接到网络。
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#### 自定义 Linux 网桥 ####
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如果你想自定义网桥，你可以执行以下步骤。你可以在这个网桥后面分配一个子网，并为这个子网分配地址。下面的命令会为 Docker 子网分配 10.0.0.0/24 地址段：
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$ sudo apt-get install bridge-utils
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$ sudo brctl addbr br0
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$ sudo ifconfig br0 10.0.0.1 netmask 255.255.255.0
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然后在 /etc/default/docker.io 文件的 DOCKER_OPTS 变量里添加“-b=br0”选项，并重启 Docker 服务：
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$ sudo service docker.io restart
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到目前为止，任何创建的容器都会连上 br0 网桥，它们的 IP 地址会从 10.0.0.0/24 中自动分配（译注：在10.0.0.2到10.0.0.254之间随机分配）。
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#### 其他自定义设置 ####
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你可以通过 /etc/default/docker.io 文件的 DOCKER_OPTS 变量设置其他一些属性：
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- "-dns 8.8.8.8 -dns 8.8.4.4": 为容器指定 DNS 服务器。
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- "-icc=false": 将容器与其他容器隔离出来
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### 疑难解答 ###
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1、当你运行 docker.io 命令时，你可能会遇到以下问题：
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> dial unix /var/run/docker.sock: no such file or directory
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这个错误可能是由于 Docker 后台进程没有启动。检查下 Docker 后台进程的状态，确认它已经处于启动状态：
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$ sudo service docker.io status
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$ sudo service docker.io start
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--------------------------------------------------------------------------------
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via: http://xmodulo.com/2014/05/manage-linux-containers-docker-ubuntu.html
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译者：[bazz2](https://github.com/bazz2) 校对：[校对者ID](https://github.com/校对者ID)
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本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创翻译，[Linux中国](http://linux.cn/) 荣誉推出
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[1]:https://linuxcontainers.org/
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[2]:https://www.docker.io/
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[3]:http://blog.docker.io/2014/04/docker-in-ubuntu-ubuntu-in-docker/
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[4]:http://www.redhat.com/about/news/press-archive/2014/4/red-hat-docker-expand-collaboration
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[5]:http://mwhiteley.com/linux-containers/2013/08/31/docker-on-i386.html
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[6]:http://xmodulo.com/go/ubuntubook
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