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diff --git a/content/devops/lxc_howto.rst b/content/devops/lxc_howto.rst new file mode 100644 index 0000000..514e02f --- /dev/null +++ b/content/devops/lxc_howto.rst @@ -0,0 +1,116 @@ +Notes: LXC How-To +################# + +:date: 2014-12-26 08:11 +:slug: lxc_howto +:tags: lxc, container, debian +:author: copyninja +:summary: A short how to on LXC basics + +LXC - Linux Containers allows us to run multiple isolated Linux system +under same control host. This will be useful for testing application +without changing our existing system. + +To create an LXC container we use the `lxc-create` command, it can +accepts the template option, with which we can choose the OS we would +like to run under the virtual isolated environment. On a Debian system +I see following templates supported + +.. code-block:: shell + + [vasudev@rudra: ~/ ]% ls /usr/share/lxc/templates + lxc-alpine* lxc-archlinux* lxc-centos* lxc-debian* lxc-fedora* lxc-openmandriva* lxc-oracle* lxc-sshd* lxc-ubuntu-cloud* + lxc-altlinux* lxc-busybox* lxc-cirros* lxc-download* lxc-gentoo* lxc-opensuse* lxc-plamo* lxc-ubuntu* + +For my application testing I wanted to create a Debian container for +my By default the template provided by lxc package creates Debian +stable container. This can be changed by passing the option to +debootstrap after `--` as shown below. + +.. code-block:: shell + + sudo MIRROR=http://localhost:9999/debian lxc-create -t debian \ + -f container.conf -n container-name -- -r sid + +`-r` switch is used to specify the release, MIRROR environment +variable is used to choose the required Debian mirror. I wanted to use +my own local *approx* installation, so I can save some bandwidth. + +`container.conf` is the configuration file used for creating the LXC, +in my case it contains basic information on how container networking +should b setup. The configuration is basically taken from `LXC Debian +wiki <https://wiki.debian.org/LXC>`_ + +.. code-block:: ini + + lxc.utsname = aptoffline-dev + lxc.network.type = veth + lxc.network.flags = up + lxc.network.link = br0.1 + lxc.network.name = eth0 + lxc.network.ipv4 = 192.168.3.2/24 + lxc.network.veth.pair = vethvm1 + +I'm using VLAN setup described in `Debian wiki: LXC VLAN Networking +<https://wiki.debian.org/LXC/VlanNetworking>`_ page. Below is my +`interfaces` file. + +:: + + iface eth0.1 inet manual + + iface br0.1 inet manual + bridge_ports eth0.1 + bridge_fd 0 + bridge_maxwait 0 + +Before launching the LXC make sure you run below command + +.. code-block:: shell + + sudo ifup eth0.1 + sudo ifup br0.1 + + # Also give ip to bridge in same subnet as lxc.network.ipv4 + sudo ip addr add 192.168.3.1/24 dev br0.1 + +I'm giving ip address to bridge so that I can communicate with +container from my control host, once it comes up. + +Now start the container using below command + +.. code-block:: shell + + sudo lxc-start -n container -d -c tty8 + +We are starting lxc in daemon mode and attaching it to console +`tty8`. If you want, you can drop -d and -c option to start lxc in +foreground. But its better you start it in background and attach using +`lxc-console` command shown below. + +.. code-block:: shell + + sudo lxc-console -n container -t tty8 + +You can detach from console using `Ctrl+a q` combination and let lxc +execute in background. + +Its also possible to simply ssh into the running container since we +have enabled networking. + +Stopping the container should be done using `lxc-stop` command, but +without `-k` switch (kill) this command never returned. Even with +timeout container is not stopped. + +.. code-block:: shell + + sudo lxc-stop -n container + +`-r` can be used for reboot of container. Since I couldn't get clean +shutdown I normally attach the console and issue a `halt` command in +container itself. Not sure if this is the right way, but it gets the +thing done. + +I consider Linux container as a better alternative for spawning a +virtual Linux environment instead of running a full blown VM like +Virtualbox or VMware. |