Add guide on running devstack in lxc container
Running OpenStack in a container can be a useful workflow for developers. The primary benefits are faster performance and lower memory overhead while still providing a suitable level of isolation. The guide walks the user through procedure for configuring an LXC container and deploying OpenStack in it using devstack. It also discusses the limitations of this setup - particularly related to cinder. Change-Id: I2e0921fd118cfe98cef86ba110a94b3edccf9a29
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Cody A.W. Somerville
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doc/source/guides/lxc.rst
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doc/source/guides/lxc.rst
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================================
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All-In-One Single LXC Container
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================================
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This guide walks you through the process of deploying OpenStack using devstack
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in an LXC container instead of a VM.
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The primary benefits to running devstack inside a container instead of a VM is
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faster performance and lower memory overhead while still providing a suitable
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level of isolation. This can be particularly useful when you want to simulate
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running OpenStack on multiple nodes.
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.. Warning:: Containers do not provide the same level of isolation as a virtual
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machine.
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.. Note:: Not all OpenStack features support running inside of a container. See
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`Limitations`_ section below for details. :doc:`OpenStack in a VM <single-vm>`
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is recommended for beginners.
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Prerequisites
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==============
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This guide is written for Ubuntu 14.04 but should be adaptable for any modern
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Linux distribution.
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Install the LXC package::
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sudo apt-get install lxc
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You can verify support for containerization features in your currently running
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kernel using the ``lxc-checkconfig`` command.
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Container Setup
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===============
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Configuration
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---------------
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For a successful run of ``stack.sh`` and to permit use of KVM to run the VMs you
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launch inside your container, we need to use the following additional
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configuration options. Place the following in a file called
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``devstack-lxc.conf``::
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# Permit access to /dev/loop*
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lxc.cgroup.devices.allow = b 7:* rwm
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# Setup access to /dev/net/tun and /dev/kvm
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lxc.mount.entry = /dev/net/tun dev/net/tun none bind,create=file 0 0
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lxc.mount.entry = /dev/kvm dev/kvm none bind,create=file 0 0
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# Networking
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lxc.network.type = veth
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lxc.network.flags = up
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lxc.network.link = lxcbr0
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Create Container
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-------------------
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The configuration and rootfs for LXC containers are created using the
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``lxc-create`` command.
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We will name our container ``devstack`` and use the ``ubuntu`` template which
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will use ``debootstrap`` to build a Ubuntu rootfs. It will default to the same
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release and architecture as the host system. We also install the additional
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packages ``bsdmainutils`` and ``git`` as we'll need them to run devstack::
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sudo lxc-create -n devstack -t ubuntu -f devstack-lxc.conf -- --packages=bsdmainutils,git
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The first time it builds the rootfs will take a few minutes to download, unpack,
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and configure all the necessary packages for a minimal installation of Ubuntu.
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LXC will cache this and subsequent containers will only take seconds to create.
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.. Note:: To speed up the initial rootfs creation, you can specify a mirror to
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download the Ubuntu packages from by appending ``--mirror=`` and then the URL
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of a Ubuntu mirror. To see other other template options, you can run
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``lxc-create -t ubuntu -h``.
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Start Container
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----------------
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To start the container, run::
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sudo lxc-start -n devstack
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A moment later you should be presented with the login prompt for your container.
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You can login using the username ``ubuntu`` and password ``ubuntu``.
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You can also ssh into your container. On your host, run
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``sudo lxc-info -n devstack`` to get the IP address (e.g.
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``ssh ubuntu@$(sudo lxc-info -n p2 | awk '/IP/ { print $2 }')``).
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Run Devstack
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-------------
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You should now be logged into your container and almost ready to run devstack.
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The commands in this section should all be run inside your container.
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.. Tip:: You can greatly reduce the runtime of your initial devstack setup by
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ensuring you have your apt sources.list configured to use a fast mirror.
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Check and update ``/etc/apt/sources.list`` if necessary and then run
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``apt-get update``.
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#. Download DevStack
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::
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git clone https://git.openstack.org/openstack-dev/devstack
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#. Configure
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Refer to :ref:`minimal-configuration` if you wish to configure the behaviour
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of devstack.
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#. Start the install
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::
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cd devstack
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./stack.sh
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Cleanup
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-------
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To stop the container::
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lxc-stop -n devstack
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To delete the container::
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lxc-destroy -n devstack
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Limitations
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============
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Not all OpenStack features may function correctly or at all when ran from within
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a container.
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Cinder
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-------
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Unable to create LVM backed volume
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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In our configuration, we have not whitelisted access to device-mapper or LVM
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devices. Doing so will permit your container to have access and control of LVM
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on the host system. To enable, add the following to your
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``devstack-lxc.conf`` before running ``lxc-create``::
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lxc.cgroup.devices.allow = c 10:236 rwm
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lxc.cgroup.devices.allow = b 252:* rwm
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Additionally you'll need to set ``udev_rules = 0`` in the ``activation``
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section of ``/etc/lvm/lvm.conf`` unless you mount devtmpfs in your container.
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Unable to attach volume to instance
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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It is not possible to attach cinder volumes to nova instances due to parts of
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the Linux iSCSI implementation not being network namespace aware. This can be
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worked around by using network pass-through instead of a separate network
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namespace but such a setup significantly reduces the isolation of the
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container (e.g. a ``halt`` command issued in the container will cause the host
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system to shutdown).
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@ -76,6 +76,7 @@ Walk through various setups used by stackers
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guides/single-vm
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guides/single-machine
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guides/lxc
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guides/multinode-lab
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guides/neutron
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guides/devstack-with-nested-kvm
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@ -96,6 +97,13 @@ Run :doc:`OpenStack on dedicated hardware <guides/single-machine>` This can inc
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server-class machine or a laptop at home.
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:doc:`[Read] <guides/single-machine>`
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All-In-One LXC Container
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-------------------------
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Run :doc:`OpenStack in a LXC container <guides/lxc>`. Beneficial for intermediate
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and advanced users. The VMs launched in this cloud will be fully accelerated but
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not all OpenStack features are supported. :doc:`[Read] <guides/lxc>`
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Multi-Node Lab
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--------------
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