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[translated] How to create and manage LXC containers on Ubuntu
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[bazz222222222]
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How to create and manage LXC containers on Ubuntu
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================================================================================
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While the concept of containers was introduced more than a decade ago to manage shared hosting environments securely (e.g., FreeBSD jails), Linux containers such as LXC or [Docker][1] have gone mainstream only recently with the rising need to deploy applications for the cloud. While [Docker][2] is getting all the media spotlight these days with strong backing from major cloud providers (e.g., Amazon AWS, Microsoft Azure) and distro providers (e.g., Red Hat, Ubuntu), LXC is in fact the original container technology developed for Linux platforms.
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If you are an average Linux user, what good does Docker/LXC bring to you? Well, containers are actually a great means to switch between distros literally instantly. Suppose your current desktop is Debian. You want Debian's stability. At the same time, you also want to play the latest Ubuntu games. Then instead of bothering to dual boot into a Ubuntu partition, or boot up a heavyweight Ubuntu VM, simply spin off a Ubuntu container on the spot, and you are done.
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Even without all the goodies of Docker, what I like about LXC containers is the fact that LXC can be managed by libvirt interface, which is not the case for Docker. If you have been using libvirt-based management tools (e.g., virt-manager or virsh), you can use those same tools to manage LXC containers.
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In this tutorial, I focus on the command-line usage of standard LXC container tools, and demonstrate **how to create and manage LXC containers from the command line on Ubuntu**.
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### Install LXC on Ubuntu ###
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To use LXC on Ubuntu, install LXC user-space tools as follows.
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$ sudo apt-get install lxc
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After that, check the current Linux kernel for LXC support by running lxc-checkconifg tool. If everything is enabled, kernel's LXC support is ready.
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$ lxc-checkconfig
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After installing LXC tools, you will find that an LXC's default bridge interface (lxcbr0) is automatically created (as configured in /etc/lxc/default.conf).
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When you create an LXC container, the container's interface will automatically be attached to this bridge, so the container can communicate with the world.
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### Create an LXC Container ###
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To be able to create an LXC container of a particular target environment (e.g., Debian Wheezy 64bit), you need a corresponding LXC template. Fortunately, LXC user space tools on Ubuntu come with a collection of ready-made LXC templates. You can find available LXC templates in /usr/share/lxc/templates directory.
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$ ls /usr/share/lxc/templates
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An LXC template is nothing more than a script which builds a container for a particular Linux environment. When you create an LXC container, you need to use one of these templates.
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To create a Ubuntu container, for example, use the following command-line:
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$ sudo lxc-create -n <container-name> -t ubuntu
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By default, it will create a minimal Ubuntu install of the same release version and architecture as the local host, in this case Saucy Salamander (13.10) 64-bit.
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If you want, you can create Ubuntu containers of any arbitrary version by passing the release parameter. For example, to create a Ubuntu 14.10 container:
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$ sudo lxc-create -n <container-name> -t ubuntu -- --release utopic
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It will download and validate all the packages needed by a target container environment. The whole process can take a couple of minutes or more depending on the type of container. So be patient.
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After a series of package downloads and validation, an LXC container image are finally created, and you will see a default login credential to use. The container is stored in /var/lib/lxc/<container-name>. Its root filesystem is found in /var/lib/lxc/<container-name>/rootfs.
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All the packages downloaded during LXC creation get cached in /var/cache/lxc, so that creating additional containers with the same LXC template will take no time.
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Let's see a list of LXC containers on the host:
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$ sudo lxc-ls --fancy
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NAME STATE IPV4 IPV6 AUTOSTART
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------------------------------------
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test-lxc STOPPED - - NO
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To boot up a container, use the command below. The "-d" option launches the container as a daemon. Without this option, you will directly be attached to console right after you launch the container.
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$ sudo lxc-start -n <container-name> -d
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After launching the container, let's check the state of the container again:
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$ sudo lxc-ls --fancy
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NAME STATE IPV4 IPV6 AUTOSTART
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-----------------------------------------
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lxc RUNNING 10.0.3.55 - NO
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You will see that the container is in "RUNNING" state with an IP address assigned to it.
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You can also verify that the container's interface (e.g., vethJ06SFL) is automatically attached to LXC's internal bridge (lxcbr0) as follows.
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$ brctl show lxcbr0
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### Manage an LXC Container ###
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Now that we know how to create and start an LXC container, let's see what we can do with a running container.
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First of all, we want to access the container's console. For this, type this command:
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$ sudo lxc-console -n <container-name>
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Type <Ctrl+a q> to exit the console.
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To stop and destroy a container:
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$ sudo lxc-stop -n <container-name>
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$ sudo lxc-destroy -n <container-name>
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To clone an existing container to another, use these commands:
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$ sudo lxc-stop -n <container-name>
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$ sudo lxc-clone -o <container-name> -n <new-container-name>
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### Troubleshooting ###
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For those of you who encounter errors with LXC, here are some troubleshooting tips.
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1. You fail to create an LXC container with the following error.
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$ sudo lxc-create -n test-lxc -t ubuntu
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----------
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lxc-create: symbol lookup error: /usr/lib/x86_64-linux-gnu/liblxc.so.1: undefined symbol: cgmanager_get_pid_cgroup_abs_sync
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This means that you are running the latest LXC, but with an older libcgmanager. To fix this problem, you need to update libcgmanager.
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$ sudo apt-get install libcgmanager0
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--------------------------------------------------------------------------------
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via: http://xmodulo.com/lxc-containers-ubuntu.html
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作者：[Dan Nanni][a]
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译者：[译者ID](https://github.com/译者ID)
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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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[a]:http://xmodulo.com/author/nanni
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[1]:http://xmodulo.com/docker-containers-centos-fedora.html
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[2]:http://xmodulo.com/manage-linux-containers-docker-ubuntu.html
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@ -0,0 +1,141 @@
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教你在 Ubuntu 上使用 LXC 容器
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使用“容器”来保证主机环境的安全性，这个概念早在十年前就已经存在（例如 FreeBSD 的 jail 虚拟化技术），但是直到最近，随着部署云架构需求越来越多，像 LXC 和 [Docker][1] 这种 Linux 下的容器才成为被关注的焦点。当然，由于主流厂商（云供应商如亚马逊主推 AWS，微软主推 Azure；发行版如红帽、Ubuntu等）组成的强大靠山，[Docker][2] 已经被放在媒体的聚光灯下面，其实，Docker 里面所谓的“容器”技术是由 LXC 提供的。
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你只是一个普通的 Linux 用户，那 Docker/LXC 能为你带来什么好处呢？容器可以将你的应用在不同的 Linux 发行版之间迁移。想像一下这个场景：你正在用的发行版是 Debian，你喜欢它的稳定性，同时你又想玩一款最新的 Ubuntu 游戏，你不需要在电脑上装双系统然后重启进入 Ubuntu，也不需要在 Debian 上跑一个耗资源的 Ubuntu 虚拟机，你只需要简单地生成一个 Ubuntu 容器就够了。
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抛开 Docker 的好处不谈，让我们聊一下 LXC 容器的好处：我可以使用 libvirt 提供的接口来管理 LXC，这些接口和 Docker 没有任何关系。如果你有使用基于 libvirt 库的管理工具（例如 virt-manager 和 virsh），你就可以使用它们来管理 LXC 容器。
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在这篇教程中，我只介绍标准 LXC 容器管理工具的命令行操作，来教你**如何在 Ubuntu 下创建和管理 LXC 容器**。
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### Ubuntu 下安装 LXC ###
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使用下面的命令安装 LXC 在用户态的工具：
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$ sudo apt-get install lxc
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然后检查当前内核是否支持 LXC。如果所有结果都是“enable”，说明内核支持：
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$ lxc-checkconfig
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安装完 LXC 工具后，就能看到 LXC 自动创建了一块桥接网卡（lxcbr0，在 /etc/lxc/default.conf 中设置）。
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当你创建了 LXC 容器后，它的网口会自动链接到这个桥接网卡上，然后这个容器就能和外部世界通信了。
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### 创建 LXC 容器 ###
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为了在指定环境下（比如 Debian Wheezy 64位）创建 LXC 容器，你需要一个相应的 LXC 模板。幸运的是 LXC 提供的工具集成了一整套现成的 LXC 模板，你可以在 /usr/share/lxc/templates 目录下找到它们。
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$ ls /usr/share/lxc/templates
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一个 LXC 模板实质上就是一个脚本，用于创建指定环境下的容器。当你创建 LXC 容器时，你需要用到它们。
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比如你要新建 Ubuntu 容器，使用下面的命令即可：
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$ sudo lxc-create -n <container-name> -t ubuntu
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默认情况下，这个命令会创建一个最小的 Ubuntu 环境，版本号与你的宿主机一致，我这边是“活泼的蝾螈”（版本号是13.10），64位。
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当然你也可以创建任何你喜欢的版本，只要在命令里面加一个版本参数即可。举个例子，创建 Ubuntu 14.10 的容器：
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$ sudo lxc-create -n <container-name> -t ubuntu -- --release utopic
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这个命令就会下载安装指定环境下的软件包，创建新容器。整个过程需要几分钟时间，与容器的类型有关，所以，你可能需要耐心等待。
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下载安装完所有软件包后，LXC 容器镜像就创建完成了，你可以看到默认的登录界面。容器被放到 /var/lib/lxc/<容器名> 这个目录下，容器的根文件系统放在 /var/lib/lxc/<容器名>/rootfs 目录下。
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创建过程中下载的软件包保存在 /var/cache/lxc 目录下面，当你想另外建一个一样的容器时，可以省去很多下载时间。
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用下面的命令看看主机上所有的 LXC 容器：
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$ sudo lxc-ls --fancy
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NAME STATE IPV4 IPV6 AUTOSTART
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------------------------------------
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test-lxc STOPPED - - NO
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使用下面的命令启动容器。参数“-d”将容器作为后台进程打开。如果没有指定这个参数，你可以在控制台界面上直接把容器的运行程序关闭（LCTT：Ctrl+C组合键）。
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$ sudo lxc-start -n <container-name> -d
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开容器后，看看状态：
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$ sudo lxc-ls --fancy
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NAME STATE IPV4 IPV6 AUTOSTART
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lxc RUNNING 10.0.3.55 - NO
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容器状态是“运行中”，容器 IP 是10.0.3.55。
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你也可以看到容器的网络接口（比如我这里是 vethJ06SFL）自动与 LXC 内部网桥（lxcbr0）连上了：
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$ brctl show lxcbr0
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### 管理 LXC 容器 ###
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我们已经学习了怎么创建和启动 LXC 容器，现在来看看怎么玩一个正在运行着的容器。
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第一步：打开容器控制台：
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$ sudo lxc-console -n <container-name>
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使用 <Crtl+a q> 退出控制台。
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停止、删除容器：
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$ sudo lxc-stop -n <container-name>
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$ sudo lxc-destroy -n <container-name>
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复制容器，用下面的命令：
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$ sudo lxc-stop -n <container-name>
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$ sudo lxc-clone -o <container-name> -n <new-container-name>
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### 常见问题 ###
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这个小节主要介绍你们在使用 LXC 过程中碰到过的问题。
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1. 创建 LXC 容器时遇到下面的错误：
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$ sudo lxc-create -n test-lxc -t ubuntu
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lxc-create: symbol lookup error: /usr/lib/x86_64-linux-gnu/liblxc.so.1: undefined symbol: cgmanager_get_pid_cgroup_abs_sync
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错误的原因是你运行了最新的 LXC，但是它所依赖的 libcgmanager 版本较老，两者不兼容。升级下 libcmanager 即可解决问题：
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$ sudo apt-get install libcgmanager0
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--------------------------------------------------------------------------------
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via: http://xmodulo.com/lxc-containers-ubuntu.html
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作者：[Dan Nanni][a]
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译者：[bazz2](https://github.com/bazz2)
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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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[a]:http://xmodulo.com/author/nanni
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[1]:http://xmodulo.com/docker-containers-centos-fedora.html
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[2]:http://xmodulo.com/manage-linux-containers-docker-ubuntu.html
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