The OpenStack Compute service allows you to control an Infrastructure-as-a-Service (IaaS) cloud computing platform. It gives you control over instances and networks, and allows you to manage access to the cloud through users and projects. Compute does not include any virtualization software. Instead, it defines drivers that interact with underlying virtualization mechanisms that run on your host operating system, and exposes functionality over a web-based API.

Compute controls hypervisors through an API server. Selecting the best hypervisor to use can be difficult, and you must take budget, resource constraints, supported features, and required technical specifications into account. However, the majority of OpenStack development is done on systems using KVM and Xen-based hypervisors. For a detailed list of features and support across different hypervisors, see http://wiki.openstack.org/HypervisorSupportMatrix. You can also orchestrate clouds using multiple hypervisors in different availability zones. Compute supports the following hypervisors: Baremetal Hyper-V Kernel-based Virtual Machine (KVM) Linux Containers (LXC) Quick Emulator (QEMU) User Mode Linux (UML) VMWare vSphere Xen For more information about hypervisors, see the Hypervisors section in the OpenStack Configuration Reference.

The Compute system is designed to be used by different consumers in the form of tenants on a shared system, and role-based access assignments. Roles control the actions that a user is allowed to perform. Tenants are isolated resource containers that form the principal organizational structure within the Compute service. They consist of an individual VLAN, and volumes, instances, images, keys, and users. A user can specify the tenant by appending :project_id to their access key. If no tenant is specified in the API request, Compute attempts to use a tenant with the same ID as the user. For tenants, quota controls are available to limit the: number of volumes that may be launched. number of processor cores and the amount of RAM that can be allocated. floating IP addresses assigned to any instance when it launches. This allows instances to have the same publicly accessible IP addresses. fixed IP addresses assigned to the same instance when it launches. This allows instances to have the same publicly or privately accessible IP addresses. Roles control the actions a user is allowed to perform. By default, most actions do not require a particular role, but you can configure them by editing the policy.json file for user roles. For example, a rule can be defined so that a user must have the admin role in order to be able to allocate a public IP address. A tenant limits users' access to particular images. Each user is assigned a username and password. Keypairs granting access to an instance are enabled for each user, but quotas are set, so that each tenant can control resource consumption across available hardware resources. Earlier versions of OpenStack used the term project instead of tenant. Because of this legacy terminology, some command-line tools use --project_id where you would normally expect to enter a tenant ID.

Disk images provide templates for virtual machine file systems. The Glance service manages storage and management of images. Instances are the individual virtual machines that run on physical compute nodes. Users can launch any number of instances from the same image. Each launched instance runs from a copy of the base image so that any changes made to the instance do not affect the base image. You can take snapshots of running instances to create an image based on the current disk state of a particular instance. The Compute services manages instances. For more information about creating and troubleshooting images, see the OpenStack Virtual Machine Image Guide. For more information about image configuration options, see the Image Services section of the OpenStack Configuration Reference. When you launch an instance, you must choose a flavor, which represents a set of virtual resources. Flavors define how many virtual CPUs an instance has and the amount of RAM and size of its ephemeral disks. OpenStack provides a number of predefined flavors that you can edit or add to. Users must select from the set of available flavors defined on their cloud. For more information about flavors, see the Flavors section in the OpenStack Operations Guide. You can add and remove additional resources from running instances, such as persistent volume storage, or public IP addresses. The example used in this chapter is of a typical virtual system within an OpenStack cloud. It uses the cinder-volume service, which provides persistent block storage, instead of the ephemeral storage provided by the selected instance flavor. This diagram shows the system state prior to launching an instance. The image store, fronted by the image service, Glance, has a number of predefined images. Inside the cloud, a compute node contains the available vCPU, memory, and local disk resources. Additionally, the cinder-volume service provides a number of predefined volumes.

To launch an instance, select an image, a flavor, and other optional attributes. The selected flavor provides a root volume, labeled vda in this diagram, and additional ephemeral storage, labeled vdb. In this example, the cinder-volume store is mapped to the third virtual disk on this instance, vdc.

The base image is copied from the image store to the local disk. The local disk is the first disk that the instance accesses, and is labeled vda. By using smaller images, your instances start up faster as less data needs to be copied across the network. A new empty disk, labeled vdb is also created. This is an empty ephemeral disk, which is destroyed when you delete the instance. The compute node is attached to the cinder-volume using iSCSI, and maps to the third disk, vdc. The vCPU and memory resources are provisioned and the instance is booted from vda. The instance runs and changes data on the disks as indicated in red in the diagram. Some of the details in this example scenario might be different in your environment. Specifically, you might use a different type of back-end storage or different network protocols. One common variant is that the ephemeral storage used for volumes vda and vdb could be backed by network storage rather than a local disk. When the instance is deleted, the state is reclaimed with the exception of the persistent volume. The ephemeral storage is purged, memory and vCPU resources are released. The image remains unchanged throughout.

OpenStack Compute contains several main components. The cloud controller represents the global state and interacts with the other components. The API server acts as the web services front end for the cloud controller. The compute controller provides compute server resources and usually also contains the Compute service. The object store is an optional component that provides storage services. An auth manager provides authentication and authorization services when used with the Compute system, or you can use the identity service as a separate authentication service instead. A volume controller provides fast and permanent block-level storage for the compute servers. The network controller provides virtual networks to enable compute servers to interact with each other and with the public network. The scheduler is used to select the most suitable compute controller to host an instance. Compute uses a messaging-based, shared nothing architecture. All major components exist on multiple servers, including the compute, volume, and network controllers, and the object store or image service. The state of the entire system is stored in a database. The cloud controller communicates with the internal object store using HTTP, but it communicates with the scheduler, network controller, and volume controller using AMQP (advanced message queueing protocol). To avoid blocking a component while waiting for a response, Compute uses asynchronous calls, with a callback that is triggered when a response is received.

OpenStack provides two classes of block storage: ephemeral storage and persistent volumes. Volumes are persistent virtualized block devices independent of any particular instance. Ephemeral storage is associated with a single unique instance, and it exists only for the life of that instance. The amount of ephemeral storage is defined by the flavor of the instance. Generally, the root file system for an instance will be stored on ephemeral storage. It persists across reboots of the guest operating system, but when the instance is deleted, the ephemeral storage is also removed. In addition to the ephemeral root volume, all flavors except the smallest, m1.tiny, also provide an additional ephemeral block device of between 20 and 160GB. These sizes can be configured to suit your environment. This is presented as a raw block device with no partition table or file system. Cloud-aware operating system images can discover, format, and mount these storage devices. For example, the cloud-init package included in Ubuntu's stock cloud images format this space as an ext3 file system and mount it on /mnt. This is a feature of the guest operating system you are using, and is not an OpenStack mechanism. OpenStack only provisions the raw storage. Persistent volumes are created by users and their size is limited only by the user's quota and availability limits. Upon initial creation, volumes are raw block devices without a partition table or a file system. To partition or format volumes, you must attach them to an instance. Once they are attached to an instance, you can use persistent volumes in much the same way as you would use external hard disk drive. You can attach volumes to only one instance at a time, although you can detach and reattach volumes to as many different instances as you like. Persistent volumes can be configured as bootable and used to provide a persistent virtual instance similar to traditional non-cloud-based virtualization systems. Typically, the resulting instance can also still have ephemeral storage depending on the flavor selected, but the root file system can be on the persistent volume and its state maintained even if the instance is shut down. For more information about this type of configuration, see the OpenStack Configuration Reference. Persistent volumes do not provide concurrent access from multiple instances. That type of configuration requires a traditional network file system like NFS or CIFS, or a cluster file system such as GlusterFS. These systems can be built within an OpenStack cluster or provisioned outside of it, but OpenStack software does not provide these features.

The OpenStack Image service discovers, registers, and retrieves virtual machine images. The service also includes a RESTful API that allows you to query VM image metadata and retrieve the actual image with HTTP requests. For more information about the API, see the OpenStack API or the Python API. The OpenStack Image service can be controlled using a command line tool. For more information about the OpenStack Image command line tool, see the Image Management section in the OpenStack User Guide. Virtual images that have been made available through the Image service can be stored in a variety of ways. In order to use these services, you must have a working installation of the Image service, with a working endpoint, and users that have been created in the Identity service. Additionally, you must meet the environment variables required by the Compute and Image clients. The Image service supports these back end stores: File system The OpenStack Image service stores virtual machine images in the file system back-end by default. This simple back end writes image files to the local file system. Object Storage service The OpenStack highly-available object storage service. S3 The Amazon S3 service. HTTP OpenStack Image Service can read virtual machine images that are available on the internet using HTTP. This store is read only. Rados block device (RBD) Stores images inside of a Ceph storage cluster using Ceph's RBD interface. GridFS Stores images using MongoDB.

OpenStack provides command line, web-based, and API-based instance management tools. Additionally, a number of third party management tools are available, using either the native API or the provided EC2-compatible API. The OpenStack python-novaclient package provides a basic command line utility, which uses the nova command. This is available as a native package for most Linux distributions, or you can install the latest version using the pip python package installer: sudo pip install python-novaclient For more information about python-novaclient and other available command line tools, see the OpenStack End User Guide. # nova --debug list connect: (10.0.0.15, 5000) send: 'POST /v2.0/tokens HTTP/1.1\r\nHost: 10.0.0.15:5000\r\nContent-Length: 116\r\ncontent-type: application/json\r\naccept-encoding: gzip, deflate\r\naccept: application/json\r\nuser-agent: python-novaclient\r\n\r\n{"auth": {"tenantName": "demoproject", "passwordCredentials": {"username": "demouser", "password": "demopassword"}}}' reply: 'HTTP/1.1 200 OK\r\n' header: Content-Type: application/json header: Vary: X-Auth-Token header: Date: Thu, 13 Sep 2012 20:27:36 GMT header: Transfer-Encoding: chunked connect: (128.52.128.15, 8774) send: u'GET /v2/fa9dccdeadbeef23ae230969587a14bf/servers/detail HTTP/1.1\r\nHost: 10.0.0.15:8774\r\nx-auth-project-id: demoproject\r\nx-auth-token: deadbeef9998823afecc3d552525c34c\r\naccept-encoding: gzip, deflate\r\naccept: application/json\r\nuser-agent: python-novaclient\r\n\r\n' reply: 'HTTP/1.1 200 OK\r\n' header: X-Compute-Request-Id: req-bf313e7d-771a-4c0b-ad08-c5da8161b30f header: Content-Type: application/json header: Content-Length: 15 header: Date: Thu, 13 Sep 2012 20:27:36 GMT !!removed matrix for validation!!

In addition to the native compute API, OpenStack provides an EC2-compatible API. This API allows EC2 legacy workflows built for EC2 to work with OpenStack. The OpenStack Configuration Reference lists configuration options for customizing this compatibility API on your OpenStack cloud. Numerous third party tools and language-specific SDKs can be used to interact with OpenStack clouds, using both native and compatibility APIs. Some of the more popular third-party tools are: Euca2ools A popular open source command line tool for interacting with the EC2 API. This is convenient for multi-cloud environments where EC2 is the common API, or for transitioning from EC2-based clouds to OpenStack. For more information, see the euca2ools site. Hybridfox A Firefox browser add-on that provides a graphical interface to many popular public and private cloud technologies, including OpenStack. For more information, see the hybridfox site. boto A Python library for interacting with Amazon Web Services. It can be used to access OpenStack through the EC2 compatibility API. For more information, see the boto project page on GitHub. fog A Ruby cloud services library. It provides methods for interacting with a large number of cloud and virtualization platforms, including OpenStack. For more information, see the fog site. php-opencloud A PHP SDK designed to work with most OpenStack- based cloud deployments, as well as Rackspace public cloud. For more information, see the php-opencloud site.

In OpenStack the base operating system is usually copied from an image stored in the OpenStack Image service. This is the most common case and results in an ephemeral instance that starts from a known template state and loses all accumulated states on shutdown. It is also possible to put an operating system on a persistent volume in the Nova-Volume or Cinder volume system. This gives a more traditional persistent system that accumulates states, which are preserved across restarts. To get a list of available images on your system run: $ nova image-list +--------------------------------------+-------------------------------+--------+--------------------------------------+ | ID | Name | Status | Server | +--------------------------------------+-------------------------------+--------+--------------------------------------+ | aee1d242-730f-431f-88c1-87630c0f07ba | Ubuntu 12.04 cloudimg amd64 | ACTIVE | | | 0b27baa1-0ca6-49a7-b3f4-48388e440245 | Ubuntu 12.10 cloudimg amd64 | ACTIVE | | | df8d56fc-9cea-4dfd-a8d3-28764de3cb08 | jenkins | ACTIVE | | +--------------------------------------+-------------------------------+--------+--------------------------------------+ The displayed image attributes are: ID Automatically generated UUID of the image Name Free form, human-readable name for image Status The status of the image. Images marked ACTIVE are available for use. Server For images that are created as snapshots of running instances, this is the UUID of the instance the snapshot derives from. For uploaded images, this field is blank. Virtual hardware templates are called flavors. The default installation provides five flavors. By default, these are configurable by admin users, however that behavior can be changed by redefining the access controls for compute_extension:flavormanage in /etc/nova/policy.json on the compute-api server. For a list of flavors that are available on your system: $ nova flavor-list +----+-----------+-----------+------+-----------+------+-------+-------------+ | ID | Name | Memory_MB | Disk | Ephemeral | Swap | VCPUs | RXTX_Factor | +----+-----------+-----------+------+-----------+------+-------+-------------+ | 1 | m1.tiny | 512 | 1 | N/A | 0 | 1 | | | 2 | m1.small | 2048 | 20 | N/A | 0 | 1 | | | 3 | m1.medium | 4096 | 40 | N/A | 0 | 2 | | | 4 | m1.large | 8192 | 80 | N/A | 0 | 4 | | | 5 | m1.xlarge | 16384 | 160 | N/A | 0 | 8 | | +----+-----------+-----------+------+-----------+------+-------+-------------+

The OpenStack Configuration Reference provides detailed information on controlling where your instances run, including ensuring a set of instances run on different compute nodes for service resiliency or on the same node for high performance inter-instance communications. Admin users can specify an exact compute node to run on using the command --availability-zone availability-zone:compute-host

You can configure Compute to generate a random administrator (root) password and inject that password into the instance. If this feature is enabled, a user can ssh to an instance without an ssh keypair. The random password appears in the output of the nova boot command. You can also view and set the admin password from the dashboard. The dashboard is configured by default to display the admin password and allow the user to modify it. If you do not want to support password injection, we recommend disabling the password fields by editing your Dashboard local_settings file (file location will vary by Linux distribution, on Fedora/RHEL/CentOS: /etc/openstack-dashboard/local_settings, on Ubuntu and Debian: /etc/openstack-dashboard/local_settings.py and on openSUSE and SUSE Linux Enterprise Server: /usr/share/openstack-dashboard/openstack_dashboard/local/local_settings.py) OPENSTACK_HYPERVISOR_FEATURE = { ... 'can_set_password': False, } For hypervisors such as KVM that use the libvirt backend, admin password injection is disabled by default. To enable it, set the following option in /etc/nova/nova.conf: [libvirt] inject_password=true When enabled, Compute will modify the password of the root account by editing the /etc/shadow file inside of the virtual machine instance. Users will only be able to ssh to the instance using the admin password if: The virtual machine image is a Linux distribution The virtual machine has been configured to allow users to ssh as the root user. This is not the case for Ubuntu cloud images, which disallow ssh to the root account by default. Compute uses the XenAPI agent to inject passwords into guests when using the XenAPI hypervisor backend. The virtual machine image must be configured with the agent for password injection to work. To support the admin password for Windows virtual machines, you must configure the Windows image to retrieve the admin password on boot by installing an agent such as cloudbase-init.

Understanding the networking configuration options helps you design the best configuration for your Compute instances.

This section offers a brief overview of each concept in networking for Compute. With the Grizzly release, you can choose to either install and configure nova-network for networking between VMs or use the Networking service (neutron) for networking. To configure Compute networking options with Neutron, see the . For each VM instance, Compute assigns to it a private IP address. (Currently, Compute with nova-network only supports Linux bridge networking that enables the virtual interfaces to connect to the outside network through the physical interface.) The network controller with nova-network provides virtual networks to enable compute servers to interact with each other and with the public network. Currently, Compute with nova-network supports these kinds of networks, implemented in different “Network Manager” types: Flat Network Manager Flat DHCP Network Manager VLAN Network Manager These networks can co-exist in a cloud system. However, because you can't yet select the type of network for a given project, you cannot configure more than one type of network in a given Compute installation. All networking options require network connectivity to be already set up between OpenStack physical nodes. OpenStack does not configure any physical network interfaces. OpenStack automatically creates all network bridges (for example, br100) and VM virtual interfaces. All machines must have a public and internal network interface (controlled by the options: public_interface for the public interface, and flat_interface and vlan_interface for the internal interface with flat / VLAN managers). The internal network interface is used for communication with VMs, it shouldn't have an IP address attached to it before OpenStack installation (it serves merely as a fabric where the actual endpoints are VMs and dnsmasq). Also, the internal network interface must be put in promiscuous mode, because it must receive packets whose target MAC address is of the guest VM, not of the host. All the network managers configure the network using network drivers. For example, the Linux L3 driver (l3.py and linux_net.py), which makes use of iptables, route and other network management facilities, and libvirt's network filtering facilities. The driver isn't tied to any particular network manager; all network managers use the same driver. The driver usually initializes (creates bridges and so on) only when the first VM lands on this host node. All network managers operate in either single-host or multi-host mode. This choice greatly influences the network configuration. In single-host mode, a single nova-network service provides a default gateway for VMs and hosts a single DHCP server (dnsmasq). In multi-host mode, each compute node runs its own nova-network service. In both cases, all traffic between VMs and the outer world flows through nova-network. Each mode has its pros and cons. Read more in the OpenStack Configuration Reference. Compute makes a distinction between fixed IPs and floating IPs for VM instances. Fixed IPs are IP addresses that are assigned to an instance on creation and stay the same until the instance is explicitly terminated. By contrast, floating IPs are addresses that can be dynamically associated with an instance. A floating IP address can be disassociated and associated with another instance at any time. A user can reserve a floating IP for their project. In Flat Mode, a network administrator specifies a subnet. The IP addresses for VM instances are grabbed from the subnet, and then injected into the image on launch. Each instance receives a fixed IP address from the pool of available addresses. A system administrator may create the Linux networking bridge (typically named br100, although this configurable) on the systems running the nova-network service. All instances of the system are attached to the same bridge, configured manually by the network administrator. The configuration injection currently only works on Linux-style systems that keep networking configuration in /etc/network/interfaces. In Flat DHCP Mode, OpenStack starts a DHCP server (dnsmasq) to pass out IP addresses to VM instances from the specified subnet in addition to manually configuring the networking bridge. IP addresses for VM instances are grabbed from a subnet specified by the network administrator. Like Flat Mode, all instances are attached to a single bridge on the compute node. In addition a DHCP server is running to configure instances (depending on single-/multi-host mode, alongside each nova-network). In this mode, Compute does a bit more configuration in that it attempts to bridge into an ethernet device (flat_interface, eth0 by default). For every instance, nova allocates a fixed IP address and configure dnsmasq with the MAC/IP pair for the VM. Dnsmasq doesn't take part in the IP address allocation process, it only hands out IPs according to the mapping done by nova. Instances receive their fixed IPs by doing a dhcpdiscover. These IPs are not assigned to any of the host's network interfaces, only to the VM's guest-side interface. In any setup with flat networking, the hosts providing the nova-network service are responsible for forwarding traffic from the private network. They also run and configure dnsmasq as a DHCP server listening on this bridge, usually on IP address 10.0.0.1 (see DHCP server: dnsmasq ). Compute can determine the NAT entries for each network, though sometimes NAT is not used, such as when configured with all public IPs or a hardware router is used (one of the HA options). Such hosts need to have br100 configured and physically connected to any other nodes that are hosting VMs. You must set the flat_network_bridge option or create networks with the bridge parameter in order to avoid raising an error. Compute nodes have iptables/ebtables entries created for each project and instance to protect against IP/MAC address spoofing and ARP poisoning. In single-host Flat DHCP mode you will be able to ping VMs through their fixed IP from the nova-network node, but you cannot ping them from the compute nodes. This is expected behavior. VLAN Network Mode is the default mode for OpenStack Compute. In this mode, Compute creates a VLAN and bridge for each project. For multiple machine installation, the VLAN Network Mode requires a switch that supports VLAN tagging (IEEE 802.1Q). The project gets a range of private IPs that are only accessible from inside the VLAN. In order for a user to access the instances in their project, a special VPN instance (code named cloudpipe) needs to be created. Compute generates a certificate and key for the user to access the VPN and starts the VPN automatically. It provides a private network segment for each project's instances that can be accessed through a dedicated VPN connection from the Internet. In this mode, each project gets its own VLAN, Linux networking bridge, and subnet. The subnets are specified by the network administrator, and are assigned dynamically to a project when required. A DHCP Server is started for each VLAN to pass out IP addresses to VM instances from the subnet assigned to the project. All instances belonging to one project are bridged into the same VLAN for that project. OpenStack Compute creates the Linux networking bridges and VLANs when required.

The Compute service uses dnsmasq as the DHCP server when running with either that Flat DHCP Network Manager or the VLAN Network Manager. The nova-network service is responsible for starting up dnsmasq processes. The behavior of dnsmasq can be customized by creating a dnsmasq configuration file. Specify the config file using the dnsmasq_config_file configuration option. For example: dnsmasq_config_file=/etc/dnsmasq-nova.conf See the OpenStack Configuration Reference for an example of how to change the behavior of dnsmasq using a dnsmasq configuration file. The dnsmasq documentation has a more comprehensive dnsmasq configuration file example. Dnsmasq also acts as a caching DNS server for instances. You can explicitly specify the DNS server that dnsmasq should use by setting the dns_server configuration option in /etc/nova/nova.conf. The following example would configure dnsmasq to use Google's public DNS server: dns_server=8.8.8.8 Dnsmasq logging output goes to the syslog (typically /var/log/syslog or /var/log/messages, depending on Linux distribution). The dnsmasq logging output can be useful for troubleshooting if VM instances boot successfully but are not reachable over the network. A network administrator can run nova-manage fixed reserve --address=x.x.x.x to specify the starting point IP address (x.x.x.x) to reserve with the DHCP server. This reservation only affects which IP address the VMs start at, not the fixed IP addresses that the nova-network service places on the bridges.

The Compute service uses a special metadata service to enable virtual machine instances to retrieve instance-specific data. Instances access the metadata service at http://169.254.169.254. The metadata service supports two sets of APIs: an OpenStack metadata API and an EC2-compatible API. Each of the APIs is versioned by date. To retrieve a list of supported versions for the OpenStack metadata API, make a GET request to http://169.254.169.254/openstack For example: $ curl http://169.254.169.254/openstack 2012-08-10 latest To retrieve a list of supported versions for the EC2-compatible metadata API, make a GET request to http://169.254.169.254 For example: $ curl http://169.254.169.254 1.0 2007-01-19 2007-03-01 2007-08-29 2007-10-10 2007-12-15 2008-02-01 2008-09-01 2009-04-04 latest If you write a consumer for one of these APIs, always attempt to access the most recent API version supported by your consumer first, then fall back to an earlier version if the most recent one is not available. Metadata from the OpenStack API is distributed in JSON format. To retrieve the metadata, make a GET request to: http://169.254.169.254/openstack/2012-08-10/meta_data.json For example: $ curl http://169.254.169.254/openstack/2012-08-10/meta_data.json {"uuid": "d8e02d56-2648-49a3-bf97-6be8f1204f38", "availability_zone": "nova", "hostname": "test.novalocal", "launch_index": 0, "meta": {"priority": "low", "role": "webserver"}, "public_keys": {"mykey": "ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAAAgQDYVEprvtYJXVOBN0XNKVVRNCRX6BlnNbI+USLGais1sUWPwtSg7z9K9vhbYAPUZcq8c/s5S9dg5vTHbsiyPCIDOKyeHba4MUJq8Oh5b2i71/3BISpyxTBH/uZDHdslW2a+SrPDCeuMMoss9NFhBdKtDkdG9zyi0ibmCP6yMdEX8Q== Generated by Nova\n"}, "name": "test"} Here is the same content after having run through a JSON pretty-printer: { "availability_zone": "nova", "hostname": "test.novalocal", "launch_index": 0, "meta": { "priority": "low", "role": "webserver" }, "name": "test", "public_keys": { "mykey": "ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAAAgQDYVEprvtYJXVOBN0XNKVVRNCRX6BlnNbI+USLGais1sUWPwtSg7z9K9vhbYAPUZcq8c/s5S9dg5vTHbsiyPCIDOKyeHba4MUJq8Oh5b2i71/3BISpyxTBH/uZDHdslW2a+SrPDCeuMMoss9NFhBdKtDkdG9zyi0ibmCP6yMdEX8Q== Generated by Nova\n" }, "uuid": "d8e02d56-2648-49a3-bf97-6be8f1204f38" } Instances also retrieve user data (passed as the user_data parameter in the API call or by the --user_data flag in the nova boot command) through the metadata service, by making a GET request to: http://169.254.169.254/openstack/2012-08-10/user_data For example: $ curl http://169.254.169.254/openstack/2012-08-10/user_data#!/bin/bash echo 'Extra user data here' The metadata service has an API that is compatible with version 2009-04-04 of the Amazon EC2 metadata service; virtual machine images that are designed for EC2 work properly with OpenStack. The EC2 API exposes a separate URL for each metadata. You can retrieve a listing of these elements by making a GET query to: http://169.254.169.254/2009-04-04/meta-data/ For example: $ curl http://169.254.169.254/2009-04-04/meta-data/ami-id ami-launch-index ami-manifest-path block-device-mapping/ hostname instance-action instance-id instance-type kernel-id local-hostname local-ipv4 placement/ public-hostname public-ipv4 public-keys/ ramdisk-id reservation-id security-groups $ curl http://169.254.169.254/2009-04-04/meta-data/block-device-mapping/ami $ curl http://169.254.169.254/2009-04-04/meta-data/placement/ availability-zone $ curl http://169.254.169.254/2009-04-04/meta-data/public-keys/ 0=mykey Instances can retrieve the public SSH key (identified by keypair name when a user requests a new instance) by making a GET request to: http://169.254.169.254/2009-04-04/meta-data/public-keys/0/openssh-key For example: $ curl http://169.254.169.254/2009-04-04/meta-data/public-keys/0/openssh-key ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAAAgQDYVEprvtYJXVOBN0XNKVVRNCRX6BlnNbI+USLGais1sUWPwtSg7z9K9vhbYAPUZcq8c/s5S9dg5vTHbsiyPCIDOKyeHba4MUJq8Oh5b2i71/3BISpyxTBH/uZDHdslW2a+SrPDCeuMMoss9NFhBdKtDkdG9zyi0ibmCP6yMdEX8Q== Generated by Nova Instances can retrieve user data by making a GET request to: http://169.254.169.254/2009-04-04/user-data For example: $ curl http://169.254.169.254/2009-04-04/user-data #!/bin/bash echo 'Extra user data here' The metadata service is implemented by either the nova-api service or the nova-api-metadata service. (The nova-api-metadata service is generally only used when running in multi-host mode, see the OpenStack Configuration Reference for details). If you are running the nova-api service, you must have metadata as one of the elements of the list of the enabled_apis configuration option in /etc/nova/nova.conf. The default enabled_apis configuration setting includes the metadata service, so you should not need to modify it. To enable instances to reach the metadata service, the nova-network service configures iptables to NAT port 80 of the 169.254.169.254 address to the IP address specified in metadata_host (default $my_ip, which is the IP address of the nova-network service) and port specified in metadata_port (default 8775) in /etc/nova/nova.conf. The metadata_host configuration option must be an IP address, not a host name. The default Compute service settings assume that the nova-network service and the nova-api service are running on the same host. If this is not the case, you must make this change in the /etc/nova/nova.conf file on the host running the nova-network service: Set the metadata_host configuration option to the IP address of the host where the nova-api service runs.

Be sure you enable access to your VMs by using the euca-authorize or nova secgroup-add-rule command. These commands enable you to ping and ssh to your VMs: You must run these commands as root only if the credentials used to interact with nova-api are in /root/.bashrc. If the EC2 credentials are the .bashrc file for another user, you must run these commands as the user. Run nova commands: $ nova secgroup-add-rule default icmp -1 -1 0.0.0.0/0 $ nova secgroup-add-rule default tcp 22 22 0.0.0.0/0 Using euca2ools: $ euca-authorize -P icmp -t -1:-1 -s 0.0.0.0/0 default $ euca-authorize -P tcp -p 22 -s 0.0.0.0/0 default If you still cannot ping or SSH your instances after issuing the nova secgroup-add-rule commands, look at the number of dnsmasq processes that are running. If you have a running instance, check to see that TWO dnsmasq processes are running. If not, perform this as root: # killall dnsmasq # service nova-network restart

This section describes how to configure floating IP addresses if you opt to use nova-network instead of neutron for OpenStack Networking. For instructions on how to configure neutron to provide access to instances through floating IP addresses, see .

Every virtual instance is automatically assigned a private IP address. You can optionally assign public IP addresses to instances. The term floating IP refers to an IP address, typically public, that you can dynamically add to a running virtual instance. OpenStack Compute uses Network Address Translation (NAT) to assign floating IPs to virtual instances. If you plan to use this feature, you must add edit the /etc/nova/nova.conf file to specify to which interface the nova-network service binds public IP addresses, as follows: public_interface=vlan100 If you make changes to the /etc/nova/nova.conf file while the nova-network service is running, you must restart the service. Because floating IPs are implemented by using a source NAT (SNAT rule in iptables), security groups can show inconsistent behavior if VMs use their floating IP to communicate with other VMs, particularly on the same physical host. Traffic from VM to VM across the fixed network does not have this issue, and so this is the recommended path. To ensure that traffic does not get SNATed to the floating range, explicitly set dmz_cidr=x.x.x.x/y. The x.x.x.x/y value specifies the range of floating IPs for each pool of floating IPs that you define. If the VMs in the source group have floating IPs, this configuration is also required.

By default, IP forwarding is disabled on most Linux distributions. To use the floating IP feature, you must enable IP forwarding. You must enable IP forwarding on only the nodes that run the nova-network service. If you use multi_host mode, make sure to enable it on all compute nodes. Otherwise, enable it on only the node that runs the nova-network service. To check if the forwarding is enabled, run this command: $ cat /proc/sys/net/ipv4/ip_forward 0 Alternatively, you can run this command: $ sysctl net.ipv4.ip_forward net.ipv4.ip_forward = 0 In this example, IP forwarding is disabled. To enable it dynamically, run this command: # sysctl -w net.ipv4.ip_forward=1 Or: # echo 1 > /proc/sys/net/ipv4/ip_forward To make the changes permanent, edit the /etc/sysctl.conf file and update the IP forwarding setting: net.ipv4.ip_forward = 1 Save the file and run this command to apply the changes: $ sysctl -p You can also update the setting by restarting the network service. For example, on Ubuntu, run this command: $/etc/init.d/procps.sh restart On RHEL/Fedora/CentOS, run this command: $ service network restart

Nova maintains a list of floating IP addresses that you can assign to instances. Use the nova-manage floating create command to add entries to this list. For example: $ nova-manage floating create --pool=nova --ip_range=68.99.26.170/31 You can use the following nova-manage commands to perform floating IP operations: nova-manage floating list Lists the floating IP addresses in the pool. nova-manage floating create --pool=[pool name] --ip_range=[CIDR] Creates specific floating IPs for either a single address or a subnet. nova-manage floating delete [CIDR] Removes floating IP addresses using the same parameters as the create command. For information about how administrators can associate floating IPs with instances, see Manage IP addresses in the OpenStack Admin User Guide.

You can configure the nova-network service to automatically allocate and assign a floating IP address to virtual instances when they are launched. Add the following line to the /etc/nova/nova.conf file and restart the nova-network service: auto_assign_floating_ip=True If you enable this option and all floating IP addresses have already been allocated, the nova boot command fails.

You cannot remove a network that has already been associated to a project by simply deleting it. To determine the project ID you must have admin rights. You can disassociate the project from the network with a scrub command and the project ID as the final parameter: $ nova-manage project scrub --project=<id>

The multi-nic feature allows you to plug more than one interface to your instances, making it possible to make several use cases available: SSL Configurations (VIPs) Services failover/ HA Bandwidth Allocation Administrative/ Public access to your instances Each VIF is representative of a separate network with its own IP block. Every network mode introduces it's own set of changes regarding the mulitnic usage:

In order to use the multinic feature, first create two networks, and attach them to your project: $ nova network-create first-net --fixed-range-v4=20.20.0.0/24 --project-id=$your-project $ nova network-create second-net --fixed-range-v4=20.20.10.0/24 --project-id=$your-project Now every time you spawn a new instance, it gets two IP addresses from the respective DHCP servers: $ nova list +-----+------------+--------+----------------------------------------+ | ID | Name | Status | Networks | +-----+------------+--------+----------------------------------------+ | 124 | Server 124 | ACTIVE | network2=20.20.0.3; private=20.20.10.14| +-----+------------+--------+----------------------------------------+ Make sure to power up the second interface on the instance, otherwise that last won't be reachable through its second IP. Here is an example of how to setup the interfaces within the instance (this is the configuration that needs to be applied inside the image): /etc/network/interfaces # The loopback network interface auto lo iface lo inet loopback auto eth0 iface eth0 inet dhcp auto eth1 iface eth1 inet dhcp If the Virtual Network Service Neutron is installed, it is possible to specify the networks to attach to the respective interfaces by using the --nic flag when invoking the nova command: $ nova boot --image ed8b2a37-5535-4a5f-a615-443513036d71 --flavor 1 --nic net-id= <id of first network> --nic net-id= <id of first network> test-vm1

If you cannot reach your instances through the floating IP address, make sure the default security group allows ICMP (ping) and SSH (port 22), so that you can reach the instances: $ nova secgroup-list-rules default +-------------+-----------+---------+-----------+--------------+ | IP Protocol | From Port | To Port | IP Range | Source Group | +-------------+-----------+---------+-----------+--------------+ | icmp | -1 | -1 | 0.0.0.0/0 | | | tcp | 22 | 22 | 0.0.0.0/0 | | +-------------+-----------+---------+-----------+--------------+ Ensure the NAT rules have been added to iptables on the node that nova-network is running on, as root: # iptables -L -nv -A nova-network-OUTPUT -d 68.99.26.170/32 -j DNAT --to-destination 10.0.0.3 # iptables -L -nv -t nat -A nova-network-PREROUTING -d 68.99.26.170/32 -j DNAT --to-destination10.0.0.3 -A nova-network-floating-snat -s 10.0.0.3/32 -j SNAT --to-source 68.99.26.170 Check that the public address, in this example "68.99.26.170", has been added to your public interface: You should see the address in the listing when you enter "ip addr" at the command prompt. $ ip addr 2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP qlen 1000 link/ether xx:xx:xx:17:4b:c2 brd ff:ff:ff:ff:ff:ff inet 13.22.194.80/24 brd 13.22.194.255 scope global eth0 inet 68.99.26.170/32 scope global eth0 inet6 fe80::82b:2bf:fe1:4b2/64 scope link valid_lft forever preferred_lft forever Note that you cannot SSH to an instance with a public IP from within the same server as the routing configuration won't allow it. You can use tcpdump to identify if packets are being routed to the inbound interface on the compute host. If the packets are reaching the compute hosts but the connection is failing, the issue may be that the packet is being dropped by reverse path filtering. Try disabling reverse path filtering on the inbound interface. For example, if the inbound interface is eth2, as root: # sysctl -w net.ipv4.conf.eth2.rp_filter=0 If this solves your issue, add this line to /etc/sysctl.conf so that the reverse path filter is disabled the next time the compute host reboots: net.ipv4.conf.rp_filter=0 To help debug networking issues with reaching VMs, you can disable the firewall by setting the following option in /etc/nova/nova.conf: firewall_driver=nova.virt.firewall.NoopFirewallDriver We strongly recommend you remove this line to re-enable the firewall once your networking issues have been resolved. If you can SSH to your instances but you find that the network interactions to your instance is slow, or if you find that running certain operations are slower than they should be (for example, sudo), then there may be packet loss occurring on the connection to the instance. Packet loss can be caused by Linux networking configuration settings related to bridges. Certain settings can cause packets to be dropped between the VLAN interface (for example, vlan100) and the associated bridge interface (for example, br100) on the host running the nova-network service. One way to check if this is the issue in your setup is to open up three terminals and run the following commands: In the first terminal, on the host running nova-network, use tcpdump to monitor DNS-related traffic (UDP, port 53) on the VLAN interface. As root: # tcpdump -K -p -i vlan100 -v -vv udp port 53 In the second terminal, also on the host running nova-network, use tcpdump to monitor DNS-related traffic on the bridge interface. As root: # tcpdump -K -p -i br100 -v -vv udp port 53 In the third terminal, SSH inside of the instance and generate DNS requests by using the nslookup command: $ nslookup www.google.com The symptoms may be intermittent, so try running nslookup multiple times. If the network configuration is correct, the command should return immediately each time. If it is not functioning properly, the command hangs for several seconds. If the nslookup command sometimes hangs, and there are packets that appear in the first terminal but not the second, then the problem may be due to filtering done on the bridges. Try to disable filtering, as root: # sysctl -w net.bridge.bridge-nf-call-arptables=0 # sysctl -w net.bridge.bridge-nf-call-iptables=0 # sysctl -w net.bridge.bridge-nf-call-ip6tables=0 If this solves your issue, add this line to /etc/sysctl.conf so that these changes take effect the next time the host reboots: net.bridge.bridge-nf-call-arptables=0 net.bridge.bridge-nf-call-iptables=0 net.bridge.bridge-nf-call-ip6tables=0 Some administrators have observed an issue with the KVM hypervisor where instances running Ubuntu 12.04 sometimes loses network connectivity after functioning properly for a period of time. Some users have reported success with loading the vhost_net kernel module as a workaround for this issue (see bug #997978) . This kernel module may also improve network performance on KVM. To load the kernel module, as root: # modprobe vhost_net Loading the module has no effect on running instances.

The Block Storage Service provides persistent block storage resources that OpenStack Compute instances can consume. See the OpenStack Configuration Reference for information about configuring volume drivers and creating and attaching volumes to server instances.

By understanding how the different installed nodes interact with each other you can administer the Compute installation. Compute offers many ways to install using multiple servers but the general idea is that you can have multiple compute nodes that control the virtual servers and a cloud controller node that contains the remaining Compute services. The Compute cloud works through the interaction of a series of daemon processes named nova-* that reside persistently on the host machine or machines. These binaries can all run on the same machine or be spread out on multiple boxes in a large deployment. The responsibilities of Services, Managers, and Drivers, can be a bit confusing at first. Here is an outline the division of responsibilities to make understanding the system a little bit easier. Currently, Services are nova-api, nova-objectstore (which can be replaced with Glance, the OpenStack Image Service), nova-compute, and nova-network. Managers and Drivers are specified by configuration options and loaded using utils.load_object(). Managers are responsible for a certain aspect of the system. It is a logical grouping of code relating to a portion of the system. In general other components should be using the manager to make changes to the components that it is responsible for. nova-api. Receives xml requests and sends them to the rest of the system. It is a wsgi app that routes and authenticate requests. It supports the EC2 and OpenStack APIs. There is a nova-api.conf file created when you install Compute. nova-objectstore: The nova-objectstore service is an ultra simple file-based storage system for images that replicates most of the S3 API. It can be replaced with OpenStack Image Service and a simple image manager or use OpenStack Object Storage as the virtual machine image storage facility. It must reside on the same node as nova-compute. nova-compute. Responsible for managing virtual machines. It loads a Service object which exposes the public methods on ComputeManager through Remote Procedure Call (RPC). nova-network. Responsible for managing floating and fixed IPs, DHCP, bridging and VLANs. It loads a Service object which exposes the public methods on one of the subclasses of NetworkManager. Different networking strategies are available to the service by changing the network_manager configuration option to FlatManager, FlatDHCPManager, or VlanManager (default is VLAN if no other is specified).

These basic categories describe the service architecture and what's going on within the cloud controller. At the heart of the cloud framework is an API server. This API server makes command and control of the hypervisor, storage, and networking programmatically available to users in realization of the definition of cloud computing. The API endpoints are basic HTTP web services which handle authentication, authorization, and basic command and control functions using various API interfaces under the Amazon, Rackspace, and related models. This enables API compatibility with multiple existing tool sets created for interaction with offerings from other vendors. This broad compatibility prevents vendor lock-in. A messaging queue brokers the interaction between compute nodes (processing), the networking controllers (software which controls network infrastructure), API endpoints, the scheduler (determines which physical hardware to allocate to a virtual resource), and similar components. Communication to and from the cloud controller is by HTTP requests through multiple API endpoints. A typical message passing event begins with the API server receiving a request from a user. The API server authenticates the user and ensures that the user is permitted to issue the subject command. Availability of objects implicated in the request is evaluated and, if available, the request is routed to the queuing engine for the relevant workers. Workers continually listen to the queue based on their role, and occasionally their type host name. When such listening produces a work request, the worker takes assignment of the task and begins its execution. Upon completion, a response is dispatched to the queue which is received by the API server and relayed to the originating user. Database entries are queried, added, or removed as necessary throughout the process. Compute workers manage computing instances on host machines. The API dispatches commands to compute workers to complete these tasks: Run instances Terminate instances Reboot instances Attach volumes Detach volumes Get console output The Network Controller manages the networking resources on host machines. The API server dispatches commands through the message queue, which are subsequently processed by Network Controllers. Specific operations include: Allocate fixed IP addresses Configuring VLANs for projects Configuring networks for compute nodes

Access to the Euca2ools (ec2) API is controlled by an access and secret key. The user’s access key needs to be included in the request, and the request must be signed with the secret key. Upon receipt of API requests, Compute verifies the signature and runs commands on behalf of the user. To begin using Compute, you must create a user with the Identity Service.

A system administrator can use these tools to manage a cloud; the nova client, the nova-manage command, and the Euca2ools commands. The nova-manage command can only be run by cloud administrators. Both nova client and euca2ools can be used by all users, though specific commands might be restricted by Role Based Access Control in the Identity Service. Installing the python-novaclient gives you a nova shell command that enables Compute API interactions from the command line. You install the client, and then provide your user name and password, set as environment variables for convenience, and then you can have the ability to send commands to your cloud on the command-line. To install python-novaclient, download the tarball from http://pypi.python.org/pypi/python-novaclient/2.6.3#downloads and then install it in your favorite python environment. $ curl -O http://pypi.python.org/packages/source/p/python-novaclient/python-novaclient-2.6.3.tar.gz $ tar -zxvf python-novaclient-2.6.3.tar.gz $ cd python-novaclient-2.6.3 $ sudo python setup.py install Now that you have installed the python-novaclient, confirm the installation by entering: $ nova help usage: nova [--version] [--debug] [--os-cache] [--timings] [--timeout <seconds>] [--os-username <auth-user-name>] [--os-password <auth-password>] [--os-tenant-name <auth-tenant-name>] [--os-tenant-id <auth-tenant-id>] [--os-auth-url <auth-url>] [--os-region-name <region-name>] [--os-auth-system <auth-system>] [--service-type <service-type>] [--service-name <service-name>] [--volume-service-name <volume-service-name>] [--endpoint-type <endpoint-type>] [--os-compute-api-version <compute-api-ver>] [--os-cacert <ca-certificate>] [--insecure] [--bypass-url <bypass-url>] <subcommand> ... This command returns a list of nova commands and parameters. Set the required parameters as environment variables to make running commands easier. You can add --os-username, for example, on the nova command, or set it as environment variables: $ export OS_USERNAME=joecool $ export OS_PASSWORD=coolword $ export OS_TENANT_NAME=coolu Using the Identity Service, you are supplied with an authentication endpoint, which nova recognizes as the OS_AUTH_URL. $ export OS_AUTH_URL=http://hostname:5000/v2.0 $ export NOVA_VERSION=1.1 The nova-manage command may be used to perform many essential functions for administration and ongoing maintenance of nova, such as network creation or user manipulation. The man page for nova-manage has a good explanation for each of its functions, and is recommended reading for those starting out. Access it by running: $ man nova-manage For administrators, the standard pattern for executing a nova-manage command is: $ nova-manage category command [args] For example, to obtain a list of all projects: $ nova-manage project list Run without arguments to see a list of available command categories: $ nova-manage You can also run with a category argument such as user to see a list of all commands in that category: $ nova-manage service For a command-line interface to EC2 API calls, use the euca2ools command line tool. See http://open.eucalyptus.com/wiki/Euca2oolsGuide_v1.3

Add this line to the /etc/nova/nova.conf file to specify a configuration file to change the logging behavior. To change the logging level, such as DEBUG, INFO, WARNING, ERROR): log-config=/etc/nova/logging.conf The log config file is an ini-style config file which must contain a section called logger_nova, which controls the behavior of the logging facility in the nova-* services. The file must contain a section called logger_nova, for example:[logger_nova] level = INFO handlers = stderr qualname = nova This example sets the debugging level to INFO (which less verbose than the default DEBUG setting). See the Python documentation on logging configuration file format for more details on this file, including the meaning of the handlers and quaname variables. See etc/nova/logging_sample.conf in the openstack/nova repository on GitHub for an example logging.conf file with various handlers defined. You can configure OpenStack Compute services to send logging information to syslog. This is useful if you want to use rsyslog, which forwards the logs to a remote machine. You need to separately configure the Compute service (Nova), the Identity Service (Keystone), the Image Service (Glance), and, if you are using it, the Block Storage Service (Cinder) to send log messages to syslog. To do so, add these lines to: /etc/nova/nova.conf /etc/keystone/keystone.conf /etc/glance/glance-api.conf /etc/glance/glance-registry.conf /etc/cinder/cinder.conf verbose = False debug = False use_syslog = True syslog_log_facility = LOG_LOCAL0 In addition to enabling syslog, these settings also turn off more verbose output and debugging output from the log. While the example above uses the same local facility for each service (LOG_LOCAL0, which corresponds to syslog facility LOCAL0), we recommend that you configure a separate local facility for each service, as this provides better isolation and more flexibility. For example, you may want to capture logging info at different severity levels for different services. Syslog allows you to define up to seven local facilities, LOCAL0, LOCAL1, ..., LOCAL7. See the syslog documentation for more details. Rsyslog is a useful tool for setting up a centralized log server across multiple machines. We briefly describe the configuration to set up an rsyslog server; a full treatment of rsyslog is beyond the scope of this document. We assume rsyslog has already been installed on your hosts, which is the default on most Linux distributions. This example shows a minimal configuration for /etc/rsyslog.conf on the log server host, which receives the log files: # provides TCP syslog reception $ModLoad imtcp $InputTCPServerRun 1024 Add to /etc/rsyslog.conf a filter rule on which looks for a host name. The example below use compute-01 as an example of a compute host name::hostname, isequal, "compute-01" /mnt/rsyslog/logs/compute-01.log On the compute hosts, create a file named /etc/rsyslog.d/60-nova.conf, with this content.# prevent debug from dnsmasq with the daemon.none parameter *.*;auth,authpriv.none,daemon.none,local0.none -/var/log/syslog # Specify a log level of ERROR local0.error @@172.20.1.43:1024 Once you have created this file, restart your rsyslog daemon. Error-level log messages on the compute hosts should now be sent to your log server.

Before starting migrations, review the Configure migrations section in OpenStack Configuration Reference. Migration provides a scheme to migrate running instances from one OpenStack Compute server to another OpenStack Compute server. Look at the running instances, to get the ID of the instance you wish to migrate. # nova list Look at information associated with that instance - our example is vm1 from above. # nova show d1df1b5a-70c4-4fed-98b7-423362f2c47c In this example, vm1 is running on HostB. Select the server to migrate instances to. # nova-manage service list In this example, HostC can be picked up because nova-compute is running on it. Ensure that HostC has enough resource for migration. # nova-manage service describe_resource HostC cpu:the number of cpu mem(mb):total amount of memory (MB) hdd:total amount of space for NOVA-INST-DIR/instances (GB) 1st line shows total amount of resource physical server has. 2nd line shows current used resource. 3rd line shows maximum used resource. 4th line and under shows the resource for each project. Use the nova live-migration command to migrate the instances. # nova live-migration d1df1b5a-70c4-4fed-98b7-423362f2c47c HostC Make sure instances are migrated successfully with nova list. If instances are still running on HostB, check log files (src/dest nova-compute and nova-scheduler) to determine why. While the nova command is called live-migration, under the default Compute configuration options the instances are suspended before migration. See Configure migrations in OpenStack Configuration Reference for more details.

If you have deployed Compute with a shared file system, you can quickly recover from a failed compute node. Of the two methods covered in these sections, the evacuate API is the preferred method even in the absence of shared storage. The evacuate API provides many benefits over manual recovery, such as re-attachment of volumes and floating IPs.

For KVM/libvirt compute node recovery, see the previous section. Use this procedure for other hypervisors. Identify the vms on the affected hosts, using tools such as a combination of nova list and nova show or euca-describe-instances. Here's an example using the EC2 API - instance i-000015b9 that is running on node np-rcc54: i-000015b9 at3-ui02 running nectarkey (376, np-rcc54) 0 m1.xxlarge 2012-06-19T00:48:11.000Z 115.146.93.60 You can review the status of the host by using the nova database. Some of the important information is highlighted below. This example converts an EC2 API instance ID into an OpenStack ID - if you used the nova commands, you can substitute the ID directly. You can find the credentials for your database in /etc/nova.conf. SELECT * FROM instances WHERE id = CONV('15b9', 16, 10) \G; *************************** 1. row *************************** created_at: 2012-06-19 00:48:11 updated_at: 2012-07-03 00:35:11 deleted_at: NULL ... id: 5561 ... power_state: 5 vm_state: shutoff ... hostname: at3-ui02 host: np-rcc54 ... uuid: 3f57699a-e773-4650-a443-b4b37eed5a06 ... task_state: NULL ... Armed with the information of VMs on the failed host, determine to which compute host the affected VMs should move. Run the following database command to move the VM to np-rcc46: UPDATE instances SET host = 'np-rcc46' WHERE uuid = '3f57699a-e773-4650-a443-b4b37eed5a06'; Next, if using a hypervisor that relies on libvirt (such as KVM) it is a good idea to update the libvirt.xml file (found in /var/lib/nova/instances/[instance ID]). The important changes to make are to change the DHCPSERVER value to the host ip address of the Compute host that is the VMs new home, and update the VNC IP if it isn't already 0.0.0.0. Next, reboot the VM: $ nova reboot --hard 3f57699a-e773-4650-a443-b4b37eed5a06 In theory, the above database update and nova reboot command are all that is required to recover the VMs from a failed host. However, if further problems occur, consider looking at recreating the network filter configuration using virsh, restarting the Compute services or updating the vm_state and power_state in the Compute database.

When running OpenStack compute, using a shared file system or an automated configuration tool, you could encounter a situation where some files on your compute node are using the wrong UID or GID. This causes a raft of errors, such as being unable to live migrate, or start virtual machines. This basic procedure runs on nova-compute hosts, based on the KVM hypervisor, that could help to restore the situation: Make sure you don't use numbers that are already used for some other user/group. Set the nova uid in /etc/passwd to the same number in all hosts (for example, 112). Set the libvirt-qemu uid in /etc/passwd to the same number in all hosts (for example, 119). Set the nova group in /etc/group file to the same number in all hosts (for example, 120). Set the libvirtd group in /etc/group file to the same number in all hosts (for example, 119). Stop the services on the compute node. Change all the files owned by user nova or by group nova. For example: find / -uid 108 -exec chown nova {} \; # note the 108 here is the old nova uid before the change find / -gid 120 -exec chgrp nova {} \; Repeat the steps for the libvirt-qemu owned files if those were needed to change. Restart the services. Now you can run the find command to verify that all files using the correct identifiers.

In this section describes how to manage your cloud after a disaster, and how to easily back up the persistent storage volumes. Backups are mandatory, even outside of disaster scenarios. For reference, you can find a DRP definition at http://en.wikipedia.org/wiki/Disaster_Recovery_Plan. A disaster could happen to several components of your architecture: a disk crash, a network loss, a power cut, and so on. In this example, assume the following set up: A cloud controller (nova-api, nova-objecstore, nova-network) A compute node (nova-compute) A Storage Area Network used by cinder-volumes (aka SAN) The disaster example is the worst one: a power loss. That power loss applies to the three components. Let's see what runs and how it runs before the crash: From the SAN to the cloud controller, we have an active iscsi session (used for the "cinder-volumes" LVM's VG). From the cloud controller to the compute node we also have active iscsi sessions (managed by cinder-volume). For every volume an iscsi session is made (so 14 ebs volumes equals 14 sessions). From the cloud controller to the compute node, we also have iptables/ ebtables rules which allows the access from the cloud controller to the running instance. And at least, from the cloud controller to the compute node ; saved into database, the current state of the instances (in that case "running" ), and their volumes attachment (mount point, volume id, volume status, and so on.) Now, after the power loss occurs and all hardware components restart, the situation is as follows: From the SAN to the cloud, the ISCSI session no longer exists. From the cloud controller to the compute node, the ISCSI sessions no longer exist. From the cloud controller to the compute node, the iptables and ebtables are recreated, since, at boot, nova-network reapply the configurations. From the cloud controller, instances turn into a shutdown state (because they are no longer running) Into the database, data was not updated at all, since Compute could not have guessed the crash. Before going further, and to prevent the admin to make fatal mistakes, the instances won't be lost, because no "destroy" or "terminate" command was invoked, so the files for the instances remain on the compute node. Perform these tasks in that exact order. Any extra step would be dangerous at this stage : Get the current relation from a volume to its instance, so that you can recreate the attachment. Update the database to clean the stalled state. (After that, you cannot perform the first step). Restart the instances. In other words, go from a shutdown to running state. After the restart, you can reattach the volumes to their respective instances. That step, which is not a mandatory one, exists in an SSH into the instances to reboot them. You must get the current relationship from a volume to its instance, because we re-create the attachment. You can find this relationship by running nova volume-list. Note that nova client includes the ability to get volume information from cinder. Update the database to clean the stalled state. You must restore for every volume, uses these queries to clean up the database: mysql> use cinder; mysql> update volumes set mountpoint=NULL; mysql> update volumes set status="available" where status <>"error_deleting"; mysql> update volumes set attach_status="detached"; mysql> update volumes set instance_id=0; Then, when you run nova volume-list commands, all volumes appear. You can restart the instances through the nova reboot $instance. At that stage, depending on your image, some instances completely reboot and become reachable, while others stop on the "plymouth" stage. Do not reboot the ones that are stopped at that stage (see the fourth step). In fact it depends on whether you added an /etc/fstab entry for that volume. Images built with the cloud-init package remain in a pending state, while others skip the missing volume and start. (More information is available on help.ubuntu.com.) The idea of that stage is only to ask nova to reboot every instance, so the stored state is preserved. After the restart, you can reattach the volumes to their respective instances. Now that nova has restored the right status, it is time to perform the attachments through a nova volume-attach This simple snippet uses the created file: #!/bin/bash while read line; do volume=`echo $line | $CUT -f 1 -d " "` instance=`echo $line | $CUT -f 2 -d " "` mount_point=`echo $line | $CUT -f 3 -d " "` echo "ATTACHING VOLUME FOR INSTANCE - $instance" nova volume-attach $instance $volume $mount_point sleep 2 done < $volumes_tmp_file At that stage, instances that were pending on the boot sequence (plymouth) automatically continue their boot, and restart normally, while the ones that booted see the volume. If some services depend on the volume, or if a volume has an entry into fstab, it could be good to simply restart the instance. This restart needs to be made from the instance itself, not through nova. So, we SSH into the instance and perform a reboot: # shutdown -r now By completing this procedure, you can successfully recover your cloud. Follow these guidelines: Use the errors=remount parameter in the fstab file, which prevents data corruption. The system would lock any write to the disk if it detects an I/O error. This configuration option should be added into the cinder-volume server (the one which performs the ISCSI connection to the SAN), but also into the instances' fstab file. Do not add the entry for the SAN's disks to the cinder-volume's fstab file. Some systems hang on that step, which means you could lose access to your cloud-controller. To re-run the session manually, you would run the following command before performing the mount: # iscsiadm -m discovery -t st -p $SAN_IP $ iscsiadm -m node --target-name $IQN -p $SAN_IP -l For your instances, if you have the whole /home/ directory on the disk, instead of emptying the /home directory and map the disk on it, leave a user's directory with the user's bash files and the authorized_keys file. This enables you to connect to the instance, even without the volume attached, if you allow only connections through public keys. You can download from here a bash script which performs these steps: The "test mode" allows you to perform that whole sequence for only one instance. To reproduce the power loss, connect to the compute node which runs that same instance and close the iscsi session. Do not detach the volume through nova volume-detach, but instead manually close the iscsi session. In this example, the iscsi session is number 15 for that instance: $ iscsiadm -m session -u -r 15 Do not forget the -r flag. Otherwise, you close ALL sessions.