mirror of
https://github.com/ceph/ceph
synced 2024-12-21 02:42:48 +00:00
303 lines
10 KiB
ReStructuredText
303 lines
10 KiB
ReStructuredText
=================================
|
|
Using ``libvirt`` with Ceph RBD
|
|
=================================
|
|
|
|
.. index:: Ceph Block Device; livirt
|
|
|
|
The ``libvirt`` library creates a virtual machine abstraction layer between
|
|
hypervisor interfaces and the software applications that use them. With
|
|
``libvirt``, developers and system administrators can focus on a common
|
|
management framework, common API, and common shell interface (i.e., ``virsh``)
|
|
to many different hypervisors, including:
|
|
|
|
- QEMU/KVM
|
|
- XEN
|
|
- LXC
|
|
- VirtualBox
|
|
- etc.
|
|
|
|
Ceph block devices support QEMU/KVM. You can use Ceph block devices with
|
|
software that interfaces with ``libvirt``. The following stack diagram
|
|
illustrates how ``libvirt`` and QEMU use Ceph block devices via ``librbd``.
|
|
|
|
|
|
.. ditaa:: +---------------------------------------------------+
|
|
| libvirt |
|
|
+------------------------+--------------------------+
|
|
|
|
|
| configures
|
|
v
|
|
+---------------------------------------------------+
|
|
| QEMU |
|
|
+---------------------------------------------------+
|
|
| librbd |
|
|
+------------------------+-+------------------------+
|
|
| OSDs | | Monitors |
|
|
+------------------------+ +------------------------+
|
|
|
|
|
|
The most common ``libvirt`` use case involves providing Ceph block devices to
|
|
cloud solutions like OpenStack or CloudStack. The cloud solution uses
|
|
``libvirt`` to interact with QEMU/KVM, and QEMU/KVM interacts with Ceph block
|
|
devices via ``librbd``. See `Block Devices and OpenStack`_ and `Block Devices
|
|
and CloudStack`_ for details. See `Installation`_ for installation details.
|
|
|
|
You can also use Ceph block devices with ``libvirt``, ``virsh`` and the
|
|
``libvirt`` API. See `libvirt Virtualization API`_ for details.
|
|
|
|
|
|
To create VMs that use Ceph block devices, use the procedures in the following
|
|
sections. In the exemplary embodiment, we've used ``libvirt-pool`` for the pool
|
|
name, ``client.libvirt`` for the user name, and ``new-libvirt-image`` for the
|
|
image name. You may use any value you like, but ensure you replace those values
|
|
when executing commands in the subsequent procedures.
|
|
|
|
|
|
Configuring Ceph
|
|
================
|
|
|
|
To configure Ceph for use with ``libvirt``, perform the following steps:
|
|
|
|
#. `Create a pool`_ (or use the default). The following example uses the
|
|
pool name ``libvirt-pool`` with 128 placement groups. ::
|
|
|
|
ceph osd pool create libvirt-pool 128 128
|
|
|
|
Verify the pool exists. ::
|
|
|
|
ceph osd lspools
|
|
|
|
#. `Create a Ceph User`_ (or use ``client.admin`` for version 0.9.7 and
|
|
earlier). The following example uses the Ceph user name ``client.libvirt``
|
|
and references ``libvirt-pool``. ::
|
|
|
|
ceph auth get-or-create client.libvirt mon 'allow r' osd 'allow class-read object_prefix rbd_children, allow rwx pool=libvirt-pool'
|
|
|
|
Verify the name exists. ::
|
|
|
|
ceph auth list
|
|
|
|
**NOTE**: ``libvirt`` will access Ceph using the ID ``libvirt``,
|
|
not the Ceph name ``client.libvirt``. See `User Management - User`_ and
|
|
`User Management - CLI`_ for a detailed explanation of the difference
|
|
between ID and name.
|
|
|
|
#. Use QEMU to `create an image`_ in your RBD pool.
|
|
The following example uses the image name ``new-libvirt-image``
|
|
and references ``libvirt-pool``. ::
|
|
|
|
qemu-img create -f rbd rbd:libvirt-pool/new-libvirt-image 2G
|
|
|
|
Verify the image exists. ::
|
|
|
|
rbd -p libvirt-pool ls
|
|
|
|
**NOTE:** You can also use `rbd create`_ to create an image, but we
|
|
recommend ensuring that QEMU is working properly.
|
|
|
|
|
|
|
|
Preparing the VM Manager
|
|
========================
|
|
|
|
You may use ``libvirt`` without a VM manager, but you may find it simpler to
|
|
create your first domain with ``virt-manager``.
|
|
|
|
#. Install a virtual machine manager. See `KVM/VirtManager`_ for details. ::
|
|
|
|
sudo apt-get install virt-manager
|
|
|
|
#. Download an OS image (if necessary).
|
|
|
|
#. Launch the virtual machine manager. ::
|
|
|
|
sudo virt-manager
|
|
|
|
|
|
|
|
Creating a VM
|
|
=============
|
|
|
|
To create a VM with ``virt-manager``, perform the following steps:
|
|
|
|
#. Press the **Create New Virtual Machine** button.
|
|
|
|
#. Name the new virtual machine domain. In the exemplary embodiment, we
|
|
use the name ``libvirt-virtual-machine``. You may use any name you wish,
|
|
but ensure you replace ``libvirt-virtual-machine`` with the name you
|
|
choose in subsequent commandline and configuration examples. ::
|
|
|
|
libvirt-virtual-machine
|
|
|
|
#. Import the image. ::
|
|
|
|
/path/to/image/recent-linux.img
|
|
|
|
**NOTE:** Import a recent image. Some older images may not rescan for
|
|
virtual devices properly.
|
|
|
|
#. Configure and start the VM.
|
|
|
|
#. You may use ``virsh list`` to verify the VM domain exists. ::
|
|
|
|
sudo virsh list
|
|
|
|
#. Login to the VM (root/root)
|
|
|
|
#. Stop the VM before configuring it for use with Ceph.
|
|
|
|
|
|
Configuring the VM
|
|
==================
|
|
|
|
When configuring the VM for use with Ceph, it is important to use ``virsh``
|
|
where appropriate. Additionally, ``virsh`` commands often require root
|
|
privileges (i.e., ``sudo``) and will not return appropriate results or notify
|
|
you that that root privileges are required. For a reference of ``virsh``
|
|
commands, refer to `Virsh Command Reference`_.
|
|
|
|
|
|
#. Open the configuration file with ``virsh edit``. ::
|
|
|
|
sudo virsh edit {vm-domain-name}
|
|
|
|
Under ``<devices>`` there should be a ``<disk>`` entry. ::
|
|
|
|
<devices>
|
|
<emulator>/usr/bin/kvm</emulator>
|
|
<disk type='file' device='disk'>
|
|
<driver name='qemu' type='raw'/>
|
|
<source file='/path/to/image/recent-linux.img'/>
|
|
<target dev='vda' bus='virtio'/>
|
|
<address type='drive' controller='0' bus='0' unit='0'/>
|
|
</disk>
|
|
|
|
|
|
Replace ``/path/to/image/recent-linux.img`` with the path to the OS image.
|
|
The minimum kernel for using the faster ``virtio`` bus is 2.6.25. See
|
|
`Virtio`_ for details.
|
|
|
|
**IMPORTANT:** Use ``sudo virsh edit`` instead of a text editor. If you edit
|
|
the configuration file under ``/etc/libvirt/qemu`` with a text editor,
|
|
``libvirt`` may not recognize the change. If there is a discrepancy between
|
|
the contents of the XML file under ``/etc/libvirt/qemu`` and the result of
|
|
``sudo virsh dumpxml {vm-domain-name}``, then your VM may not work
|
|
properly.
|
|
|
|
|
|
#. Add the Ceph RBD image you created as a ``<disk>`` entry. ::
|
|
|
|
<disk type='network' device='disk'>
|
|
<source protocol='rbd' name='libvirt-pool/new-libvirt-image'>
|
|
<host name='{monitor-host}' port='6789'/>
|
|
</source>
|
|
<target dev='vda' bus='virtio'/>
|
|
</disk>
|
|
|
|
Replace ``{monitor-host}`` with the name of your host, and replace the
|
|
pool and/or image name as necessary. You may add multiple ``<host>``
|
|
entries for your Ceph monitors. The ``dev`` attribute is the logical
|
|
device name that will appear under the ``/dev`` directory of your
|
|
VM. The optional ``bus`` attribute indicates the type of disk device to
|
|
emulate. The valid settings are driver specific (e.g., "ide", "scsi",
|
|
"virtio", "xen", "usb" or "sata").
|
|
|
|
See `Disks`_ for details of the ``<disk>`` element, and its child elements
|
|
and attributes.
|
|
|
|
#. Save the file.
|
|
|
|
#. If your Ceph Storage Cluster has `Ceph Authentication`_ enabled (it does by
|
|
default), you must generate a secret. ::
|
|
|
|
cat > secret.xml <<EOF
|
|
<secret ephemeral='no' private='no'>
|
|
<usage type='ceph'>
|
|
<name>client.libvirt secret</name>
|
|
</usage>
|
|
</secret>
|
|
EOF
|
|
|
|
#. Define the secret. ::
|
|
|
|
sudo virsh secret-define --file secret.xml
|
|
<uuid of secret is output here>
|
|
|
|
#. Get the ``client.libvirt`` key and save the key string to a file. ::
|
|
|
|
ceph auth get-key client.libvirt | sudo tee client.libvirt.key
|
|
|
|
#. Set the UUID of the secret. ::
|
|
|
|
sudo virsh secret-set-value --secret {uuid of secret} --base64 $(cat client.libvirt.key) && rm client.libvirt.key secret.xml
|
|
|
|
You must also set the secret manually by adding the following ``<auth>``
|
|
entry to the ``<disk>`` element you entered earlier (replacing the
|
|
``uuid`` value with the result from the command line example above). ::
|
|
|
|
sudo virsh edit {vm-domain-name}
|
|
|
|
Then, add ``<auth></auth>`` element to the domain configuration file::
|
|
|
|
...
|
|
</source>
|
|
<auth username='libvirt'>
|
|
<secret type='ceph' uuid='9ec59067-fdbc-a6c0-03ff-df165c0587b8'/>
|
|
</auth>
|
|
<target ...
|
|
|
|
|
|
**NOTE:** The exemplary ID is ``libvirt``, not the Ceph name
|
|
``client.libvirt`` as generated at step 2 of `Configuring Ceph`_. Ensure
|
|
you use the ID component of the Ceph name you generated. If for some reason
|
|
you need to regenerate the secret, you will have to execute
|
|
``sudo virsh secret-undefine {uuid}`` before executing
|
|
``sudo virsh secret-set-value`` again.
|
|
|
|
|
|
Summary
|
|
=======
|
|
|
|
Once you have configured the VM for use with Ceph, you can start the VM.
|
|
To verify that the VM and Ceph are communicating, you may perform the
|
|
following procedures.
|
|
|
|
|
|
#. Check to see if Ceph is running::
|
|
|
|
ceph health
|
|
|
|
#. Check to see if the VM is running. ::
|
|
|
|
sudo virsh list
|
|
|
|
#. Check to see if the VM is communicating with Ceph. Replace
|
|
``{vm-domain-name}`` with the name of your VM domain::
|
|
|
|
sudo virsh qemu-monitor-command --hmp {vm-domain-name} 'info block'
|
|
|
|
#. Check to see if the device from ``<target dev='hdb' bus='ide'/>`` appears
|
|
under ``/dev`` or under ``proc/partitions``. ::
|
|
|
|
ls dev
|
|
cat proc/partitions
|
|
|
|
If everything looks okay, you may begin using the Ceph block device
|
|
within your VM.
|
|
|
|
|
|
.. _Installation: ../../install
|
|
.. _libvirt Virtualization API: http://www.libvirt.org
|
|
.. _Block Devices and OpenStack: ../rbd-openstack
|
|
.. _Block Devices and CloudStack: ../rbd-cloudstack
|
|
.. _Create a pool: ../../rados/operations/pools#create-a-pool
|
|
.. _Create a Ceph User: ../../rados/operations/user-management#add-a-user
|
|
.. _create an image: ../qemu-rbd#creating-images-with-qemu
|
|
.. _Virsh Command Reference: http://www.libvirt.org/virshcmdref.html
|
|
.. _KVM/VirtManager: https://help.ubuntu.com/community/KVM/VirtManager
|
|
.. _Ceph Authentication: ../../rados/configuration/auth-config-ref
|
|
.. _Disks: http://www.libvirt.org/formatdomain.html#elementsDisks
|
|
.. _rbd create: ../rados-rbd-cmds#creating-a-block-device-image
|
|
.. _User Management - User: ../../rados/operations/user-management#user
|
|
.. _User Management - CLI: ../../rados/operations/user-management#command-line-usage
|
|
.. _Virtio: http://www.linux-kvm.org/page/Virtio |