Instances and Images Guide

Red Hat OpenStack Platform 10

Managing Instances and Images

OpenStack Documentation Team

Abstract

The Instances and Images guide provides procedures for the management of instances, images of a Red Hat OpenStack Platform environment.

Preface

Red Hat OpenStack Platform (Red Hat OpenStack Platform) provides the foundation to build a private or public Infrastructure-as-a-Service (IaaS) cloud on top of Red Hat Enterprise Linux. It offers a massively scalable, fault-tolerant platform for the development of cloud-enabled workloads.

This guide discusses procedures for creating and managing images, and instances. It also mentions the procedure for configuring the storage for instances for Red Hat OpenStack Platform.

You can manage the cloud using either the OpenStack dashboard or the command-line clients. Most procedures can be carried out using either method; some of the more advanced procedures can only be executed on the command line. This guide provides procedures for the dashboard where possible.

Note

For the complete suite of documentation for Red Hat OpenStack Platform, see Red Hat OpenStack Platform Documentation Suite.

Chapter 1. Image Service

This chapter discusses the steps you can follow to manage images and storage in Red Hat OpenStack Platform.

A virtual machine image is a file that contains a virtual disk which has a bootable operating system installed on it. Virtual machine images are supported in different formats. The following are the formats available on Red Hat OpenStack Platform:

  • RAW - Unstructured disk image format.
  • QCOW2 - Disk format supported by QEMU emulator.
  • ISO - Sector-by-sector copy of the data on a disk, stored in a binary file.
  • AKI - Indicates an Amazon Kernel Image.
  • AMI - Indicates an Amazon Machine Image.
  • ARI - Indicates an Amazon RAMDisk Image.
  • VDI - Disk format supported by VirtualBox virtual machine monitor and the QEMU emulator.
  • VHD - Common disk format used by virtual machine monitors from VMware, VirtualBox, and others.
  • VMDK - Disk format supported by many common virtual machine monitors.

While ISO is not normally considered a virtual machine image format, since ISOs contain bootable filesystems with an installed operating system, you can treat them the same as you treat other virtual machine image files.

To download the official Red Hat Enterprise Linux cloud images, your account must have a valid Red Hat Enterprise Linux subscription:

You will be prompted to enter your Red Hat account credentials if you are not logged in to the Customer Portal.

1.1. Understanding the Image Service

The following notable Image service features are available:

  • Image signing and verification - Protect image integrity and authenticity by enabling deployers to sign images and save the signatures and public key certificates as image properties.

    By taking advantage of this feature, you can:

    • sign an image using your private key and upload the image, the signature, and a reference to your public key certificate (the verification metadata); the Image service then verifies that the signature is valid
    • create an image in the Compute service, have the Compute service sign the image, and upload the image and its verification metadata; the Image service again verifies that the signature is valid
    • request a signed image in the Compute service; the Image service provides the image and its verification metadata, allowing the Compute service to validate the image before booting it
  • Image conversion - Convert images by calling the task API while importing an image.

    As part of the import workflow, a plug-in provides the image conversion. This plug-in can be activated or deactivated based on the deployer configuration. Therefore, the deployer needs to specify the preferred format of images for the deployment.

    Internally, Image service receives the bits of the image in a particular format. These bits are stored in a temporary location. The plug-in is then triggered to convert the image to the target format, and moved to a final destination. When the task is finished, the temporary location is deleted. As a result, the format uploaded initially is not retained by the Image service.

    Note

    The conversion can be triggered only when importing an image (the old copy-from). It does not run when uploading an image. For example:

    $ glance --os-image-api-version 2 task-create --type import --input '{"import_from_format": "qcow2", "import_from": "http://127.0.0.1:8000/test.qcow2", "image_properties": {"disk_format": "qcow2", "container_format": "bare"}}'
  • Image Introspection - Every image format comes with a set of metadata embedded inside the image itself.

    For example, a stream optimized vmdk would contain the following parameters:

    $ head -20 so-disk.vmdk
    
    # Disk DescriptorFile
    version=1
    CID=d5a0bce5
    parentCID=ffffffff
    createType="streamOptimized"
    
    # Extent description
    RDONLY 209714 SPARSE "generated-stream.vmdk"
    
    # The Disk Data Base
    #DDB
    
    ddb.adapterType = "buslogic"
    ddb.geometry.cylinders = "102"
    ddb.geometry.heads = "64"
    ddb.geometry.sectors = "32"
    ddb.virtualHWVersion = "4"

    By introspecting this vmdk, you can easily know that the disk_type is streamOptimized, and the adapter_type is buslogic. By doing this metadata extraction in the Image service, the administrator does not have to care about all of these metadata unless they want to override some of them. These metadata parameters are useful for the consumer of the image. In Compute, the workflow to instantiate a streamOptimized disk is totally different than the one to instantiate a flat disk. This new feature allows metadata extraction. You can achieve image introspection by calling the task API while importing the image.

1.2. Manage Images

The OpenStack Image service (glance) provides discovery, registration, and delivery services for disk and server images. It provides the ability to copy or snapshot a server image, and immediately store it away. Stored images can be used as a template to get new servers up and running quickly and more consistently, than installing a server operating system and individually configuring additional services.

1.2.1. Create an Image

This section provides you with the steps to manually create OpenStack-compatible images in the QCOW2 format using Red Hat Enterprise Linux 7 ISO files, Red Hat Enterprise Linux 6 ISO files, or Windows ISO files.

1.2.1.1. Use a KVM Guest Image With Red Hat OpenStack Platform

You can use a ready RHEL KVM guest QCOW2 image:

These images are configured with cloud-init and must take advantage of ec2-compatible metadata services for provisioning SSH keys in order to function properly.

Ready Windows KVM guest QCOW2 images are not available.

Note

For the KVM guest images:

  • The root account in the image is disabled, but sudo access is granted to a special user named cloud-user.
  • There is no root password set for this image.

The root password is locked in /etc/shadow by placing !! in the second field.

For an OpenStack instance, it is recommended that you generate an ssh keypair from the OpenStack dashboard or command line and use that key combination to perform an SSH public authentication to the instance as root.

When the instance is launched, this public key will be injected to it. You can then authenticate using the private key downloaded while creating the keypair.

If you do not want to use keypairs, you can use the admin password that has been set using the Inject an admin Password Into an Instance procedure.

If you want to create custom Red Hat Enterprise Linux or Windows images, see Create a Red Hat Enterprise Linux 7 Image, Create a Red Hat Enterprise Linux 6 Image, or Create a Windows Image.

1.2.1.2. Create Custom Red Hat Enterprise Linux or Windows Images

Prerequisites:

  • Linux host machine to create an image. This can be any machine on which you can install and run the Linux packages.
  • libvirt, virt-manager (run command yum groupinstall -y @virtualization). This installs all packages necessary for creating a guest operating system.
  • Libguestfs tools (run command yum install -y libguestfs-tools-c). This installs a set of tools for accessing and modifying virtual machine images.
  • A Red Hat Enterprise Linux 7 or 6 ISO file (see RHEL 7.2 Binary DVD or RHEL 6.8 Binary DVD) or a Windows ISO file. If you do not have a Windows ISO file, visit the Microsoft TechNet Evaluation Center and download an evaluation image.
  • Text editor, if you want to change the kickstart files (RHEL only).
Note

In the following procedures, all commands with the [root@host]# prompt should be run on your host machine.

1.2.1.2.1. Create a Red Hat Enterprise Linux 7 Image

This section provides you with the steps to manually create an OpenStack-compatible image in the QCOW2 format using a Red Hat Enterprise Linux 7 ISO file.

  1. Start the installation using virt-install as shown below:

    [root@host]# qemu-img create -f qcow2 rhel7.qcow2 8G
    [root@host]# virt-install --virt-type kvm --name rhel7 --ram 2048 \
    --cdrom /tmp/rhel-server-7.2-x86_64-dvd.iso \
    --disk rhel7.qcow2,format=qcow2 \
    --network=bridge:virbr0 --graphics vnc,listen=0.0.0.0 \
    --noautoconsole --os-type=linux --os-variant=rhel7

    This launches an instance and starts the installation process.

    Note

    If the instance does not launch automatically, run the virt-viewer command to view the console:

    [root@host]# virt-viewer rhel7
  2. Set up the virtual machine as follows:

    1. At the initial Installer boot menu, choose the Install Red Hat Enterprise Linux 7.X option. RHEL7 Install1
    2. Choose the appropriate Language and Keyboard options.
    3. When prompted about which type of devices your installation uses, choose Auto-detected installation media. RHEL7 Install5
    4. When prompted about which type of installation destination, choose Local Standard Disks. RHEL7 Install6 For other storage options, choose Automatically configure partitioning.
    5. For software selection, choose Minimal Install.
    6. For network and host name, choose eth0 for network and choose a hostname for your device. The default host name is localhost.localdomain.
    7. Choose the root password. RHEL7 Install9 The installation process completes and the Complete! screen appears.
  3. After the installation is complete, reboot the instance and log in as the root user.
  4. Update the /etc/sysconfig/network-scripts/ifcfg-eth0 file so it only contains the following values:

    TYPE=Ethernet
    DEVICE=eth0
    ONBOOT=yes
    BOOTPROTO=dhcp
    NM_CONTROLLED=no
  5. Reboot the machine.
  6. Register the machine with the Content Delivery Network. For details, see Subscribe to the Required Channels in Manual Installation Procedures.
  7. Update the system:

    # yum -y update
  8. Install the cloud-init packages:

    # yum install -y cloud-utils-growpart cloud-init
  9. Edit the /etc/cloud/cloud.cfg configuration file and under cloud_init_modules add:

    - resolv-conf

    The resolv-conf option automatically configures the resolv.conf when an instance boots for the first time. This file contains information related to the instance such as nameservers, domain and other options.

  10. Add the following line to /etc/sysconfig/network to avoid problems accessing the EC2 metadata service:

    NOZEROCONF=yes
  11. To ensure the console messages appear in the Log tab on the dashboard and the nova console-log output, add the following boot option to the /etc/default/grub file:

    GRUB_CMDLINE_LINUX_DEFAULT="console=tty0 console=ttyS0,115200n8"

    Run the grub2-mkconfig command:

    # grub2-mkconfig -o /boot/grub2/grub.cfg

    The output is as follows:

    Generating grub configuration file ...
    Found linux image: /boot/vmlinuz-3.10.0-229.7.2.el7.x86_64
    Found initrd image: /boot/initramfs-3.10.0-229.7.2.el7.x86_64.img
    Found linux image: /boot/vmlinuz-3.10.0-121.el7.x86_64
    Found initrd image: /boot/initramfs-3.10.0-121.el7.x86_64.img
    Found linux image: /boot/vmlinuz-0-rescue-b82a3044fb384a3f9aeacf883474428b
    Found initrd image: /boot/initramfs-0-rescue-b82a3044fb384a3f9aeacf883474428b.img
    done
  12. Un-register the virtual machine so that the resulting image does not contain the same subscription details for every instance cloned based on it:

    # subscription-manager repos --disable=*
    # subscription-manager unregister
    # yum clean all
  13. Power off the instance:

    # poweroff
  14. Reset and clean the image using the virt-sysprep command so it can be used to create instances without issues:

    [root@host]# virt-sysprep -d rhel7
  15. Reduce image size using the virt-sparsify command. This command converts any free space within the disk image back to free space within the host:

    [root@host]# virt-sparsify --compress /tmp/rhel7.qcow2 rhel7-cloud.qcow2

    This creates a new rhel7-cloud.qcow2 file in the location from where the command is run.

The rhel7-cloud.qcow2 image file is ready to be uploaded to the Image service. For more information on uploading this image to your OpenStack deployment using the dashboard, see Upload an Image.

1.2.1.2.2. Create a Red Hat Enterprise Linux 6 Image

This section provides you with the steps to manually create an OpenStack-compatible image in the QCOW2 format using a Red Hat Enterprise Linux 6 ISO file.

  1. Start the installation using virt-install:

    [root@host]# qemu-img create -f qcow2 rhel6.qcow2 4G
    [root@host]# virt-install --connect=qemu:///system --network=bridge:virbr0 \
    --name=rhel6 --os-type linux --os-variant rhel6 \
    --disk path=rhel6.qcow2,format=qcow2,size=10,cache=none \
    --ram 4096 --vcpus=2 --check-cpu --accelerate \
    --hvm --cdrom=rhel-server-6.8-x86_64-dvd.iso

    This launches an instance and starts the installation process.

    Note

    If the instance does not launch automatically, run the virt-viewer command to view the console:

    [root@host]# virt-viewer rhel6
  2. Set up the virtual machines as follows:

    1. At the initial Installer boot menu, choose the Install or upgrade an existing system option. RHEL6 Install1 Step through the installation prompts. Accept the defaults.

      The installer checks for the disc and lets you decide whether you want to test your installation media before installation. Select OK to run the test or Skip to proceed without testing.

    2. Choose the appropriate Language and Keyboard options.
    3. When prompted about which type of devices your installation uses, choose Basic Storage Devices. RHEL6 Install3
    4. Choose a hostname for your device. The default host name is localhost.localdomain.
    5. Set timezone and root password.
    6. Based on the space on the disk, choose the type of installation. RHEL6 Install4
    7. Choose the Basic Server install, which installs an SSH server. RHEL6 Install5
    8. The installation process completes and Congratulations, your Red Hat Enterprise Linux installation is complete screen appears.
  3. Reboot the instance and log in as the root user.
  4. Update the /etc/sysconfig/network-scripts/ifcfg-eth0 file so it only contains the following values:

    TYPE=Ethernet
    DEVICE=eth0
    ONBOOT=yes
    BOOTPROTO=dhcp
    NM_CONTROLLED=no
  5. Reboot the machine.
  6. Register the machine with the Content Delivery Network. For details, see Subscribe to the Required Channels in the Manual Installation Procedures guide.
  7. Update the system:

    # yum -y update
  8. Install the cloud-init packages:

    # yum install -y cloud-utils-growpart cloud-init
  9. Edit the /etc/cloud/cloud.cfg configuration file and under cloud_init_modules add:

    - resolv-conf

    The resolv-conf option automatically configures the resolv.conf configuration file when an instance boots for the first time. This file contains information related to the instance such as nameservers, domain, and other options.

  10. To prevent network issues, create the /etc/udev/rules.d/75-persistent-net-generator.rules file as follows:

    # echo "#" > /etc/udev/rules.d/75-persistent-net-generator.rules

    This prevents /etc/udev/rules.d/70-persistent-net.rules file from being created. If /etc/udev/rules.d/70-persistent-net.rules is created, networking may not function properly when booting from snapshots (the network interface is created as "eth1" rather than "eth0" and IP address is not assigned).

  11. Add the following line to /etc/sysconfig/network to avoid problems accessing the EC2 metadata service:

    NOZEROCONF=yes
  12. To ensure the console messages appear in the Log tab on the dashboard and the nova console-log output, add the following boot option to the /etc/grub.conf:

    console=tty0 console=ttyS0,115200n8
  13. Un-register the virtual machine so that the resulting image does not contain the same subscription details for every instance cloned based on it:

    # subscription-manager repos --disable=*
    # subscription-manager unregister
    # yum clean all
  14. Power off the instance:

    # poweroff
  15. Reset and clean the image using the virt-sysprep command so it can be used to create instances without issues:

    [root@host]# virt-sysprep -d rhel6
  16. Reduce image size using the virt-sparsify command. This command converts any free space within the disk image back to free space within the host:

    [root@host]# virt-sparsify --compress rhel6.qcow2 rhel6-cloud.qcow2

    This creates a new rhel6-cloud.qcow2 file in the location from where the command is run.

    Note

    You will need to manually resize the partitions of instances based on the image in accordance with the disk space in the flavor that is applied to the instance.

The rhel6-cloud.qcow2 image file is ready to be uploaded to the Image service. For more information on uploading this image to your OpenStack deployment using the dashboard, see Upload an Image

1.2.1.2.3. Create a Windows Image

This section provides you with the steps to manually create an OpenStack-compatible image in the QCOW2 format using a Windows ISO file.

  1. Start the installation using virt-install as shown below:

    [root@host]# virt-install --name=name \
    --disk size=size \
    --cdrom=path \
    --os-type=windows \
    --network=bridge:virbr0 \
    --graphics spice \
    --ram=RAM

    Replace the values of the virt-install parameters as follows:

    • name — the name that the Windows guest should have.
    • size — disk size in GB.
    • path — the path to the Windows installation ISO file.
    • RAM — the requested amount of RAM in MB.

      Note

      The --os-type=windows parameter ensures that the clock is set up correctly for the Windows guest, and enables its Hyper-V enlightenment features.

      Note that virt-install saves the guest image as /var/lib/libvirt/images/name.qcow2 by default. If you want to keep the guest image elsewhere, change the parameter of the --disk option as follows:

      --disk path=filename,size=size

      Replace filename with the name of the file which should store the guest image (and optionally its path); for example path=win8.qcow2,size=8 creates an 8 GB file named win8.qcow2 in the current working directory.

      Tip

      If the guest does not launch automatically, run the virt-viewer command to view the console:

      [root@host]# virt-viewer name
  2. Installation of Windows systems is beyond the scope of this document. For instructions on how to install Windows, see the relevant Microsoft documentation.
  3. To allow the newly installed Windows system to use the virtualized hardware, you may need to install virtio drivers in it. To so do, first install the virtio-win package on the host system. This package contains the virtio ISO image, which is to be attached as a CD-ROM drive to the Windows guest. See Chapter 8. KVM Para-virtualized (virtio) Drivers in the Virtualization Deployment and Administration Guide for detailed instructions on how to install the virtio-win package, add the virtio ISO image to the guest, and install the virtio drivers.
  4. To complete the setup, download and execute Cloudbase-Init on the Windows system. At the end of the installation of Cloudbase-Init, select the Run Sysprep and Shutdown check boxes. The Sysprep tool makes the guest unique by generating an OS ID, which is used by certain Microsoft services.

    Important

    Red Hat does not provide technical support for Cloudbase-Init. If you encounter an issue, contact Cloudbase Solutions.

When the Windows system shuts down, the name.qcow2 image file is ready to be uploaded to the Image service. For more information on uploading this image to your OpenStack deployment using the dashboard or the command line, see Upload an Image.

1.2.2. Upload an Image

  1. In the dashboard, select Project > Compute > Images.
  2. Click Create Image.
  3. Fill out the values, and click Create Image when finished.

Table 1.1. Image Options

FieldNotes

Name

Name for the image. The name must be unique within the project.

Description

Brief description to identify the image.

Image Source

Image source: Image Location or Image File. Based on your selection, the next field is displayed.

Image Location or Image File

  • Select Image Location option to specify the image location URL.
  • Select Image File option to upload an image from the local disk.

Format

Image format (for example, qcow2).

Architecture

Image architecture. For example, use i686 for a 32-bit architecture or x86_64 for a 64-bit architecture.

Minimum Disk (GB)

Minimum disk size required to boot the image. If this field is not specified, the default value is 0 (no minimum).

Minimum RAM (MB)

Minimum memory size required to boot the image. If this field is not specified, the default value is 0 (no minimum).

Public

If selected, makes the image public to all users with access to the project.

Protected

If selected, ensures only users with specific permissions can delete this image.

When the image has been successfully uploaded, its status is changed to active, which indicates that the image is available for use. Note that the Image service can handle even large images that take a long time to upload — longer than the lifetime of the Identity service token which was used when the upload was initiated. This is due to the fact that the Image service first creates a trust with the Identity service so that a new token can be obtained and used when the upload is complete and the status of the image is to be updated.

Note

You can also use the glance image-create command with the property option to upload an image. More values are available on the command line. For a complete listing, see Image Configuration Parameters.

1.2.3. Update an Image

  1. In the dashboard, select Project > Compute > Images.
  2. Click Edit Image from the dropdown list.

    Note

    The Edit Image option is available only when you log in as an admin user. When you log in as a demo user, you have the option to Launch an instance or Create Volume.

  3. Update the fields and click Update Image when finished. You can update the following values - name, description, kernel ID, ramdisk ID, architecture, format, minimum disk, minimum RAM, public, protected.
  4. Click the drop-down menu and select Update Metadata option.
  5. Specify metadata by adding items from the left column to the right one. In the left column, there are metadata definitions from the Image Service Metadata Catalog. Select Other to add metadata with the key of your choice and click Save when finished.
Note

You can also use the glance image-update command with the property option to update an image. More values are available on the command line; for a complete listing, see Image Configuration Parameters.

1.2.4. Delete an Image

  1. In the dashboard, select Project > Compute > Images.
  2. Select the image you want to delete and click Delete Images.

1.2.4.1. Purge Deleted Image Data

Information about an image is kept in the OpenStack Image Service database even after the image has been deleted. As a consequence, the database can grow in size over time and become slow to use and hard to upgrade.

To remove information about deleted images, use the glance-manage db purge command. By default, database entries are removed if they reference images deleted 30 days ago (or more), but you can specify a different amount of time (in days) as a parameter. For example, to remove information about images deleted more than 60 days ago, run the glance-manage command:

$ glance-manage db purge 60

Chapter 2. Configure OpenStack Compute Storage

This chapter describes the architecture for the back-end storage of images in OpenStack Compute (nova), and provides basic configuration options.

2.1. Architecture Overview

In Red Hat OpenStack Platform, the OpenStack Compute service uses the KVM hypervisor to execute compute workloads. The libvirt driver handles all interactions with KVM, and enables the creation of virtual machines.

Two types of libvirt storage must be considered for Compute:

  • Base image, which is a cached and formatted copy of the Image service image.
  • Instance disk, which is created using the libvirt base and is the back end for the virtual machine instance. Instance disk data can be stored either in Compute’s ephemeral storage (using the libvirt base) or in persistent storage (for example, using Block Storage).

Creation of Virtual Machines

The steps that Compute takes to create a virtual machine instance are:

  1. Cache the Image service’s backing image as the libvirt base.
  2. Convert the base image to the raw format (if configured).
  3. Resize the base image to match the VM’s flavor specifications.
  4. Use the base image to create the libvirt instance disk.

In the diagram above, the #1 instance disk uses ephemeral storage; the #2 disk uses a block-storage volume.

Ephemeral storage is an empty, unformatted, additional disk available to an instance. This storage value is defined by the instance flavor. The value provided by the user must be less than or equal to the ephemeral value defined for the flavor. The default value is 0, meaning no ephemeral storage is created.

The ephemeral disk appears in the same way as a plugged-in hard drive or thumb drive. It is available as a block device which you can check using the lsblk command. You can format it, mount it, and use it however you normally would a block device. There is no way to preserve or reference that disk beyond the instance it is attached to.

Block storage volume is persistant storage available to an instance regardless of the state of the running instance.

2.2. Configuration

Compute configuration for handling the libvirt base and instance disks can determine both performance and security aspects of your environment; parameters are configured in the /etc/nova/nova.conf file.

Table 2.1. Compute Image Parameters

SectionParameterDescriptionDefault

[DEFAULT]

force_raw_images

Whether to convert a non-raw cached base image to be raw (boolean). If a non-raw image is converted to raw, Compute:

  • Disallows backing files (which might be a security issue).
  • Removes existing compression (to avoid CPU bottlenecks).

Converting the base to raw uses more space for any image that could have been used directly by the hypervisor (for example, a qcow2 image). If you have a system with slower I/O or less available space, you might want to specify 'false', trading the higher CPU requirements of compression for that of minimized input bandwidth.

Raw base images are always used with libvirt_images_type=lvm.

true

[DEFAULT]

use_cow_images

Whether to use CoW (Copy on Write) images for libvirt instance disks (boolean):

  • false - The raw format is used. Without CoW, more space is used for common parts of the disk image
  • true - The cqow2 format is used. With CoW, depending on the backing store and host caching, there may be better concurrency achieved by having each VM operate on its own copy.

true

[DEFAULT]

preallocate_images

Preallocation mode for libvirt instance disks. Value can be:

  • none - No storage is provisioned at instance start.
  • space - Storage is fully allocated at instance start (using fallocate), which can help with both space guarantees and I/O performance.

Even when not using CoW instance disks, the copy each VM gets is sparse and so the VM may fail unexpectedly at run time with ENOSPC. By running fallocate(1) on the instance disk images, Compute immediately and efficiently allocates the space for them in the file system (if supported). Run time performance should also be improved because the file system does not have to dynamically allocate blocks at run time (reducing CPU overhead and more importantly file fragmentation).

none

[DEFAULT]

resize_fs_using_block_device

Whether to enable direct resizing of the base image by accessing the image over a block device (boolean). This is only necessary for images with older versions of cloud-init (that cannot resize themselves).

Because this parameter enables the direct mounting of images which might otherwise be disabled for security reasons, it is not enabled by default.

false

[DEFAULT]

default_ephemeral_format

The default format that is used for a new ephemeral volume. Value can be: ext2, ext3, or ext4. The ext4 format provides much faster initialization times than ext3 for new, large disks. You can also override per instance using the guest_format configuration option.

ext4

[DEFAULT]

image_cache_manager_interval

Number of seconds to wait between runs of the image cache manager, which impacts base caching on libvirt compute nodes. This period is used in the auto removal of unused cached images (see remove_unused_base_images and remove_unused_original_minimum_age_seconds).

2400

[DEFAULT]

remove_unused_base_images

Whether to enable the automatic removal of unused base images (checked every image_cache_manager_interval seconds). Images are defined as unused if they have not been accessed in remove_unused_original_minimum_age_seconds seconds.

true

[DEFAULT]

remove_unused_original_minimum_age_seconds

How old an unused base image must be before being removed from the libvirt cache (see remove_unused_base_images).

86400

[libvirt]

images_type

Image type to use for libvirt instance disks (deprecates use_cow_images). Value can be: raw, qcow2, lvm, rbd, or default. If default is specified, the value used for the use_cow_images parameter is used.

default

Chapter 3. Virtual Machine Instances

OpenStack Compute is the central component that provides virtual machines on demand. Compute interacts with the Identity service for authentication, Image service for images (used to launch instances), and the dashboard service for the user and administrative interface.

Red Hat OpenStack Platform allows you to easily manage virtual machine instances in the cloud. The Compute service creates, schedules, and manages instances, and exposes this functionality to other OpenStack components. This chapter discusses these procedures along with procedures to add components like key pairs, security groups, host aggregates and flavors. The term instance is used by OpenStack to mean a virtual machine instance.

3.1. Manage Instances

Before you can create an instance, you need to ensure certain other OpenStack components (for example, a network, key pair and an image or a volume as the boot source) are available for the instance.

This section discusses the procedures to add these components, create and manage an instance. Managing an instance refers to updating, and logging in to an instance, viewing how the instances are being used, resizing or deleting them.

3.1.1. Add Components

Use the following sections to create a network, key pair and upload an image or volume source. These components are used in the creation of an instance and are not available by default. You will also need to create a new security group to allow SSH access to the user.

  1. In the dashboard, select Project.
  2. Select Network > Networks, and ensure there is a private network to which you can attach the new instance (to create a network, see Create a Network section in the Networking Guide.
  3. Select Compute > Access & Security > Key Pairs, and ensure there is a key pair (to create a key pair, see Section 3.2.1.1, “Create a Key Pair”).
  4. Ensure that you have either an image or a volume that can be used as a boot source:

  5. Select Compute > Access & Security > Security Groups, and ensure you have created a security group rule (to create a security group, see Project Security Management in the Users and Identity Management Guide.

3.1.2. Create an Instance

  1. In the dashboard, select Project > Compute > Instances.
  2. Click Launch Instance.
  3. Fill out instance fields (those marked with '* ' are required), and click Launch when finished.

Table 3.1. Instance Options

TabFieldNotes

Project and User

Project

Select the project from the dropdown list.

 

User

Select the user from the dropdown list.

Details

Availability Zone

Zones are logical groupings of cloud resources in which your instance can be placed. If you are unsure, use the default zone (for more information, see Section 3.4, “Manage Host Aggregates”).

 

Instance Name

A name to identify your instance.

 

Flavor

The flavor determines what resources the instance is given (for example, memory). For default flavor allocations and information on creating new flavors, see Section 3.3, “Manage Flavors”.

 

Instance Count

The number of instances to create with these parameters. "1" is preselected.

 

Instance Boot Source

Depending on the item selected, new fields are displayed allowing you to select the source:

Access and Security

Key Pair

The specified key pair is injected into the instance and is used to remotely access the instance using SSH (if neither a direct login information or a static key pair is provided). Usually one key pair per project is created.

 

Security Groups

Security groups contain firewall rules which filter the type and direction of the instance’s network traffic (for more information on configuring groups, see Project Security Management in the Users and Identity Management Guide.

Networking

Selected Networks

You must select at least one network. Instances are typically assigned to a private network, and then later given a floating IP address to enable external access.

Post-Creation

Customization Script Source

You can provide either a set of commands or a script file, which will run after the instance is booted (for example, to set the instance host name or a user password). If 'Direct Input' is selected, write your commands in the Script Data field; otherwise, specify your script file.

Note

Any script that starts with '#cloud-config' is interpreted as using the cloud-config syntax (for information on the syntax, see http://cloudinit.readthedocs.org/en/latest/topics/examples.html).

Advanced Options

Disk Partition

By default, the instance is built as a single partition and dynamically resized as needed. However, you can choose to manually configure the partitions yourself.

 

Configuration Drive

If selected, OpenStack writes metadata to a read-only configuration drive that is attached to the instance when it boots (instead of to Compute’s metadata service). After the instance has booted, you can mount this drive to view its contents (enables you to provide files to the instance).

3.1.3. Update an Instance (Actions menu)

You can update an instance by selecting Project > Compute > Instances, and selecting an action for that instance in the Actions column. Actions allow you to manipulate the instance in a number of ways:

Table 3.2. Update Instance Options

ActionDescription

Create Snapshot

Snapshots preserve the disk state of a running instance. You can create a snapshot to migrate the instance, as well as to preserve backup copies.

Associate/Disassociate Floating IP

You must associate an instance with a floating IP (external) address before it can communicate with external networks, or be reached by external users. Because there are a limited number of external addresses in your external subnets, it is recommended that you disassociate any unused addresses.

Edit Instance

Update the instance’s name and associated security groups.

Edit Security Groups

Add and remove security groups to or from this instance using the list of available security groups (for more information on configuring groups, see Project Security Management in the Users and Identity Management Guide.

Console

View the instance’s console in the browser (allows easy access to the instance).

View Log

View the most recent section of the instance’s console log. Once opened, you can view the full log by clicking View Full Log.

Pause/Resume Instance

Immediately pause the instance (you are not asked for confirmation); the state of the instance is stored in memory (RAM).

Suspend/Resume Instance

Immediately suspend the instance (you are not asked for confirmation); like hibernation, the state of the instance is kept on disk.

Resize Instance

Bring up the Resize Instance window (see Section 3.1.4, “Resize an Instance”).

Soft Reboot

Gracefully stop and restart the instance. A soft reboot attempts to gracefully shut down all processes before restarting the instance.

Hard Reboot

Stop and restart the instance. A hard reboot effectively just shuts down the instance’s power and then turns it back on.

Shut Off Instance

Gracefully stop the instance.

Rebuild Instance

Use new image and disk-partition options to rebuild the image (shut down, re-image, and re-boot the instance). If encountering operating system issues, this option is easier to try than terminating the instance and starting over.

Terminate Instance

Permanently destroy the instance (you are asked for confirmation).

You can create and allocate an external IP address, see Section 3.2.3, “Create, Assign, and Release Floating IP Addresses”

3.1.4. Resize an Instance

To resize an instance (memory or CPU count), you must select a new flavor for the instance that has the right capacity. If you are increasing the size, remember to first ensure that the host has enough space.

  1. Ensure communication between hosts by setting up each host with SSH key authentication so that Compute can use SSH to move disks to other hosts (for example, compute nodes can share the same SSH key).

    For more information about setting up SSH key authentication, see Configure SSH Tunneling Between Nodes in the Migrating Instances guide.

  2. Enable resizing on the original host by setting the following parameter in the /etc/nova/nova.conf file:

    [DEFAULT] allow_resize_to_same_host = True
  3. In the dashboard, select Project > Compute > Instances.
  4. Click the instance’s Actions arrow, and select Resize Instance.
  5. Select a new flavor in the New Flavor field.
  6. If you want to manually partition the instance when it launches (results in a faster build time):

    1. Select Advanced Options.
    2. In the Disk Partition field, select Manual.
  7. Click Resize.

3.1.5. Connect to an Instance

This section discusses the different methods you can use to access an instance console using the dashboard or the command-line interface. You can also directly connect to an instance’s serial port allowing you to debug even if the network connection fails.

3.1.5.1. Access an Instance Console using the Dashboard

The console allows you a way to directly access your instance within the dashboard.

  1. In the dashboard, select Compute > Instances.
  2. Click the instance’s More button and select Console. console access
  3. Log in using the image’s user name and password (for example, a CirrOS image uses cirros/cubswin:)).

3.1.5.2. Directly Connect to a VNC Console

You can directly access an instance’s VNC console using a URL returned by nova get-vnc-console command.

Browser

To obtain a browser URL, use:

$ nova get-vnc-console INSTANCE_ID novnc
Java Client

To obtain a Java-client URL, use:

$ nova get-vnc-console INSTANCE_ID xvpvnc
Note

nova-xvpvncviewer provides a simple example of a Java client. To download the client, use:

# git clone https://github.com/cloudbuilders/nova-xvpvncviewer
# cd nova-xvpvncviewer/viewer
# make

Run the viewer with the instance’s Java-client URL:

# java -jar VncViewer.jar URL

This tool is provided only for customer convenience, and is not officially supported by Red Hat.

3.1.5.3. Directly Connect to a Serial Console

You can directly access an instance’s serial port using a websocket client. Serial connections are typically used as a debugging tool (for example, instances can be accessed even if the network configuration fails). To obtain a serial URL for a running instance, use:

$ nova get-serial-console INSTANCE_ID
Note

novaconsole provides a simple example of a websocket client. To download the client, use:

# git clone https://github.com/larsks/novaconsole/
# cd novaconsole

Run the client with the instance’s serial URL:

# python console-client-poll.py

This tool is provided only for customer convenience, and is not officially supported by Red Hat.

However, depending on your installation, the administrator may need to first set up the nova-serialproxy service. The proxy service is a websocket proxy that allows connections to OpenStack Compute serial ports.

3.1.5.3.1. Install and Configure nova-serialproxy
  1. Install the nova-serialproxy service:

    # yum install openstack-nova-serialproxy
  2. Update the serial_console section in /etc/nova/nova.conf:

    1. Enable the nova-serialproxy service:

      $ openstack-config --set /etc/nova/nova.conf serial_console enabled true
    2. Specify the string used to generate URLS provided by the nova get-serial-console command.

      $ openstack-config --set /etc/nova/nova.conf serial_console base_url ws://PUBLIC_IP:6083/

      Where PUBLIC_IP is the public IP address of the host running the nova-serialproxy service.

    3. Specify the IP address on which the instance serial console should listen (string).

      $ openstack-config --set /etc/nova/nova.conf serial_console listen 0.0.0.0
    4. Specify the address to which proxy clients should connect (string).

      $ openstack-config --set /etc/nova/nova.conf serial_console proxyclient_address ws://HOST_IP:6083/

      Where HOST_IP is the IP address of your Compute host. For example, an enabled nova-serialproxy service is as following:

      [serial_console]
      enabled=true
      base_url=ws://192.0.2.0:6083/
      listen=0.0.0.0
      proxyclient_address=192.0.2.3
  3. Restart Compute services:

    # openstack-service restart nova
  4. Start the nova-serialproxy service:

    # systemctl enable openstack-nova-serialproxy
    # systemctl start openstack-nova-serialproxy
  5. Restart any running instances, to ensure that they are now listening on the right sockets.
  6. Open the firewall for serial-console port connections. Serial ports are set using [serial_console] port_range in /etc/nova/nova.conf; by default, the range is 10000:20000. Update iptables with:

    # iptables -I INPUT 1 -p tcp --dport 10000:20000 -j ACCEPT

3.1.6. View Instance Usage

The following usage statistics are available:

  • Per Project

    To view instance usage per project, select Project > Compute > Overview. A usage summary is immediately displayed for all project instances.

    You can also view statistics for a specific period of time by specifying the date range and clicking Submit.

  • Per Hypervisor

    If logged in as an administrator, you can also view information for all projects. Click Admin > System and select one of the tabs. For example, the Resource Usage tab offers a way to view reports for a distinct time period. You might also click Hypervisors to view your current vCPU, memory, or disk statistics.

    Note

    The vCPU Usage value (x of y) reflects the number of total vCPUs of all virtual machines (x) and the total number of hypervisor cores (y).

3.1.7. Delete an Instance

  1. In the dashboard, select Project > Compute > Instances, and select your instance.
  2. Click Terminate Instance.
Note

Deleting an instance does not delete its attached volumes; you must do this separately (see Delete a Volume in the Storage Guide.

3.1.8. Manage Multiple Instances at Once

If you need to start multiple instances at the same time (for example, those that were down for compute or controller maintenance) you can do so easily at Project > Compute > Instances:

  1. Click the check boxes in the first column for the instances that you want to start. If you want to select all of the instances, click the check box in the first row in the table.
  2. Click More Actions above the table and select Start Instances.

Similarly, you can shut off or soft reboot multiple instances by selecting the respective actions.

3.2. Manage Instance Security

You can manage access to an instance by assigning it the correct security group (set of firewall rules) and key pair (enables SSH user access). Further, you can assign a floating IP address to an instance to enable external network access. The sections below outline how to create and manage key pairs, security groups, floating IP addresses and logging in to an instance using SSH. There is also a procedure for injecting an admin password in to an instance.

For information on managing security groups, see Project Security Management in the Users and Identity Management Guide.

3.2.1. Manage Key Pairs

Key pairs provide SSH access to the instances. Each time a key pair is generated, its certificate is downloaded to the local machine and can be distributed to users. Typically, one key pair is created for each project (and used for multiple instances).

You can also import an existing key pair into OpenStack.

3.2.1.1. Create a Key Pair

  1. In the dashboard, select Project > Compute > Access & Security.
  2. On the Key Pairs tab, click Create Key Pair.
  3. Specify a name in the Key Pair Name field, and click Create Key Pair.

When the key pair is created, a key pair file is automatically downloaded through the browser. Save this file for later connections from external machines. For command-line SSH connections, you can load this file into SSH by executing:

# ssh-add ~/.ssh/os-key.pem

3.2.1.2. Import a Key Pair

  1. In the dashboard, select Project > Compute > Access & Security.
  2. On the Key Pairs tab, click Import Key Pair.
  3. Specify a name in the Key Pair Name field, and copy and paste the contents of your public key into the Public Key field.
  4. Click Import Key Pair.

3.2.1.3. Delete a Key Pair

  1. In the dashboard, select Project > Compute > Access & Security.
  2. On the Key Pairs tab, click the key’s Delete Key Pair button.

3.2.2. Create a Security Group

Security groups are sets of IP filter rules that can be assigned to project instances, and which define networking access to the instance. Security group are project specific; project members can edit the default rules for their security group and add new rule sets.

  1. In the dashboard, select the Project tab, and click Compute > Access & Security.
  2. On the Security Groups tab, click + Create Security Group.
  3. Provide a name and description for the group, and click Create Security Group.

For more information on managing project security, see Project Security Management in the Users and Identity Management Guide.

3.2.3. Create, Assign, and Release Floating IP Addresses

By default, an instance is given an internal IP address when it is first created. However, you can enable access through the public network by creating and assigning a floating IP address (external address). You can change an instance’s associated IP address regardless of the instance’s state.

Projects have a limited range of floating IP address that can be used (by default, the limit is 50), so you should release these addresses for reuse when they are no longer needed. Floating IP addresses can only be allocated from an existing floating IP pool, see Create Floating IP Pools in the Networking Guide.

3.2.3.1. Allocate a Floating IP to the Project

  1. In the dashboard, select Project > Compute > Access & Security.
  2. On the Floating IPs tab, click Allocate IP to Project.
  3. Select a network from which to allocate the IP address in the Pool field.
  4. Click Allocate IP.

3.2.3.2. Assign a Floating IP

  1. In the dashboard, select Project > Compute > Access & Security.
  2. On the Floating IPs tab, click the address' Associate button.
  3. Select the address to be assigned in the IP address field.

    Note

    If no addresses are available, you can click the + button to create a new address.

  4. Select the instance to be associated in the Port to be Associated field. An instance can only be associated with one floating IP address.
  5. Click Associate.

3.2.3.3. Release a Floating IP

  1. In the dashboard, select Project > Compute > Access & Security.
  2. On the Floating IPs tab, click the address' menu arrow (next to the Associate/Disassociate button.
  3. Select Release Floating IP.

3.2.4. Log in to an Instance

Prerequisites:

To first load the key pair file into SSH, and then use ssh without naming it:

  1. Change the permissions of the generated key-pair certificate.

    $ chmod 600 os-key.pem
  2. Check whether ssh-agent is already running:

    # ps -ef | grep ssh-agent
  3. If not already running, start it up with:

    # eval `ssh-agent`
  4. On your local machine, load the key-pair certificate into SSH. For example:

    $ ssh-add ~/.ssh/os-key.pem
  5. You can now SSH into the file with the user supplied by the image.

The following example command shows how to SSH into the Red Hat Enterprise Linux guest image with the user cloud-user:

$ ssh cloud-user@192.0.2.24
Note

You can also use the certificate directly. For example:

$ ssh -i /myDir/os-key.pem cloud-user@192.0.2.24

3.2.5. Inject an admin Password Into an Instance

You can inject an admin (root) password into an instance using the following procedure.

  1. In the /etc/openstack-dashboard/local_settings file, set the change_set_password parameter value to True.

    can_set_password: True
  2. In the /etc/nova/nova.conf file, set the inject_password parameter to True.

    inject_password=true
  3. Restart the Compute service.

    # service nova-compute restart

When you use the nova boot command to launch a new instance, the output of the command displays an adminPass parameter. You can use this password to log into the instance as the root user.

The Compute service overwrites the password value in the /etc/shadow file for the root user. This procedure can also be used to activate the root account for the KVM guest images. For more information on how to use KVM guest images, see Section 1.2.1.1, “Use a KVM Guest Image With Red Hat OpenStack Platform”

You can also set a custom password from the dashboard. To enable this, run the following command after you have set can_set_password parameter to true.

# systemctl restart httpd.service

The newly added admin password fields are as follows:

dashboard

These fields can be used when you launch or rebuild an instance.

3.3. Manage Flavors

Each created instance is given a flavor (resource template), which determines the instance’s size and capacity. Flavors can also specify secondary ephemeral storage, swap disk, metadata to restrict usage, or special project access (none of the default flavors have these additional attributes defined).

Table 3.3. Default Flavors

NamevCPUsRAMRoot Disk Size

m1.tiny

1

512 MB

1 GB

m1.small

1

2048 MB

20 GB

m1.medium

2

4096 MB

40 GB

m1.large

4

8192 MB

80 GB

m1.xlarge

8

16384 MB

160 GB

The majority of end users will be able to use the default flavors. However, you can create and manage specialized flavors. For example, you can:

  • Change default memory and capacity to suit the underlying hardware needs.
  • Add metadata to force a specific I/O rate for the instance or to match a host aggregate.
Note

Behavior set using image properties overrides behavior set using flavors (for more information, see Section 1.2, “Manage Images”.

3.3.1. Update Configuration Permissions

By default, only administrators can create flavors or view the complete flavor list (select Admin > System > Flavors). To allow all users to configure flavors, specify the following in the /etc/nova/policy.json file (nova-api server):

"compute_extension:flavormanage": "",

3.3.2. Create a Flavor

  1. As an admin user in the dashboard, select Admin > System > Flavors.
  2. Click Create Flavor, and specify the following fields:

    Table 3.4. Flavor Options

    TabFieldDescription

    Flavor Information

    Name

    Unique name.

     

    ID

    Unique ID. The default value, auto, generates a UUID4 value, but you can also manually specify an integer or UUID4 value.

     

    VCPUs

    Number of virtual CPUs.

     

    RAM (MB)

    Memory (in megabytes).

     

    Root Disk (GB)

    Ephemeral disk size (in gigabytes); to use the native image size, specify 0. This disk is not used if Instance Boot Source=Boot from Volume.

     

    Epehemeral Disk (GB)

    Secondary ephemeral disk size (in gigabytes) available to an instance. This disk is destroyed when an instance is deleted.

    The default value is 0, which implies that no ephemeral disk is created.

     

    Swap Disk (MB)

    Swap disk size (in megabytes).

    Flavor Access

    Selected Projects

    Projects which can use the flavor. If no projects are selected, all projects have access (Public=Yes).

  3. Click Create Flavor.

3.3.3. Update General Attributes

  1. As an admin user in the dashboard, select Admin > System > Flavors.
  2. Click the flavor’s Edit Flavor button.
  3. Update the values, and click Save.

3.3.4. Update Flavor Metadata

In addition to editing general attributes, you can add metadata to a flavor (extra_specs), which can help fine-tune instance usage. For example, you might want to set the maximum-allowed bandwidth or disk writes.

  • Pre-defined keys determine hardware support or quotas. Pre-defined keys are limited by the hypervisor you are using (for libvirt, see Table 3.5, “Libvirt Metadata”).
  • Both pre-defined and user-defined keys can determine instance scheduling. For example, you might specify SpecialComp=True; any instance with this flavor can then only run in a host aggregate with the same key-value combination in its metadata (see Section 3.4, “Manage Host Aggregates”).

3.3.4.1. View Metadata

  1. As an admin user in the dashboard, select Admin > System > Flavors.
  2. Click the flavor’s Metadata link (Yes or No). All current values are listed on the right-hand side under Existing Metadata.

3.3.4.2. Add Metadata

You specify a flavor’s metadata using a key/value pair.

  1. As an admin user in the dashboard, select Admin > System > Flavors.
  2. Click the flavor’s Metadata link (Yes or No). All current values are listed on the right-hand side under Existing Metadata.
  3. Under Available Metadata, click on the Other field, and specify the key you want to add (see Table 3.5, “Libvirt Metadata”).
  4. Click the + button; you can now view the new key under Existing Metadata.
  5. Fill in the key’s value in its right-hand field.

    flavor metadata

  6. When finished with adding key-value pairs, click Save.

Table 3.5. Libvirt Metadata

KeyDescription

hw:action

Action that configures support limits per instance. Valid actions are:

  • cpu_max_sockets - Maximum supported CPU sockets.
  • cpu_max_cores - Maximum supported CPU cores.
  • cpu_max_threads - Maximum supported CPU threads.
  • cpu_sockets - Preferred number of CPU sockets.
  • cpu_cores - Preferred number of CPU cores.
  • cpu_threads - Preferred number of CPU threads.
  • serial_port_count - Maximum serial ports per instance.

Example: hw:cpu_max_sockets=2

hw:NUMA_def

Definition of NUMA topology for the instance. For flavors whose RAM and vCPU allocations are larger than the size of NUMA nodes in the compute hosts, defining NUMA topology enables hosts to better utilize NUMA and improve performance of the guest OS. NUMA definitions defined through the flavor override image definitions. Valid definitions are:

  • numa_nodes - Number of NUMA nodes to expose to the instance. Specify '1' to ensure image NUMA settings are overridden.
  • numa_mempolicy - Memory allocation policy. Valid policies are:

    • strict - Mandatory for the instance’s RAM allocations to come from the NUMA nodes to which it is bound (default if numa_nodes is specified).
    • preferred - The kernel can fall back to using an alternative node. Useful when the numa_nodes is set to '1'.
  • numa_cpus.0 - Mapping of vCPUs N-M to NUMA node 0 (comma-separated list).
  • numa_cpus.1 - Mapping of vCPUs N-M to NUMA node 1 (comma-separated list).
  • numa_mem.0 - Mapping N GB of RAM to NUMA node 0.
  • numa_mem.1 - Mapping N GB of RAM to NUMA node 1.
  • numa_cpu.N and numa_mem.N are only valid if numa_nodes is set. Additionally, they are only required if the instance’s NUMA nodes have an asymetrical allocation of CPUs and RAM (important for some NFV workloads).
Note

If the values of numa_cpu or numa_mem.N specify more than that available, an exception is raised.

Example when the instance has 8 vCPUs and 4GB RAM:

  • hw:numa_nodes=2
  • hw:numa_cpus.0=0,1,2,3,4,5
  • hw:numa_cpus.1=6,7
  • hw:numa_mem.0=3
  • hw:numa_mem.1=1

The scheduler looks for a host with 2 NUMA nodes with the ability to run 6 CPUs + 3 GB of RAM on one node, and 2 CPUS + 1 GB of RAM on another node. If a host has a single NUMA node with capability to run 8 CPUs and 4 GB of RAM, it will not be considered a valid match. The same logic is applied in the scheduler regardless of the numa_mempolicy setting.

hw:watchdog_action

An instance watchdog device can be used to trigger an action if the instance somehow fails (or hangs). Valid actions are:

  • disabled - The device is not attached (default value).
  • pause - Pause the instance.
  • poweroff - Forcefully shut down the instance.
  • reset - Forcefully reset the instance.
  • none - Enable the watchdog, but do nothing if the instance fails.

Example: hw:watchdog_action=poweroff

hw_rng:action

A random-number generator device can be added to an instance using its image properties (see hw_rng_model in the "Command-Line Interface Reference" in Red Hat OpenStack Platform documentation).

If the device has been added, valid actions are:

  • allowed - If True, the device is enabled; if False, disabled. By default, the device is disabled.
  • rate_bytes - Maximum number of bytes the instance’s kernel can read from the host to fill its entropy pool every rate_period (integer).
  • rate_period - Duration of the read period in seconds (integer).

Example: hw_rng:allowed=True.

hw_video:ram_max_mb

Maximum permitted RAM to be allowed for video devices (in MB).

Example: hw:ram_max_mb=64

quota:option

Enforcing limit for the instance. Valid options are:

  • cpu_period - Time period for enforcing cpu_quota (in microseconds). Within the specified cpu_period, each vCPU cannot consume more than cpu_quota of runtime. The value must be in range [1000, 1000000]; '0' means 'no value'.
  • cpu_quota - Maximum allowed bandwidth (in microseconds) for the vCPU in each `cpu_period. The value must be in range [1000, 18446744073709551]. '0' means 'no value'; a negative value means that the vCPU is not controlled. cpu_quota and cpu_period can be used to ensure that all vCPUs run at the same speed.
  • cpu_shares - Share of CPU time for the domain. The value only has meaning when weighted against other machine values in the same domain. That is, an instance with a flavor with '200' will get twice as much machine time as an instance with '100'.
  • disk_read_bytes_sec - Maximum disk reads in bytes per second.
  • disk_read_iops_sec - Maximum read I/O operations per second.
  • disk_write_bytes_sec - Maximum disk writes in bytes per second.
  • disk_write_iops_sec - Maximum write I/O operations per second.
  • disk_total_bytes_sec - Maximum total throughput limit in bytes per second.
  • disk_total_iops_sec - Maximum total I/O operations per second.
  • vif_inbound_average - Desired average of incoming traffic.
  • vif_inbound_burst - Maximum amount of traffic that can be received at vif_inbound_peak speed.
  • vif_inbound_peak - Maximum rate at which incoming traffic can be received.
  • vif_outbound_average - Desired average of outgoing traffic.
  • vif_outbound_burst - Maximum amount of traffic that can be sent at vif_outbound_peak speed.
  • vif_outbound_peak - Maximum rate at which outgoing traffic can be sent.

Example: quota:vif_inbound_average=10240

In addition, the VMware driver supports the following quota options, which control upper and lower limits for CPUs, RAM, disks, and networks, as well as shares, which can be used to control relative allocation of available resources among tenants:

  • cpu_limit - Maximum CPU frequency available to a virtual machine (in MHz).
  • cpu_reservation - Guaranteed minimum amount of CPU resources available to a virtual machine (in MHz).
  • cpu_shares_level - CPU allocation level (shares) in the case of contention. Possible values are high, normal, low, and custom.
  • cpu_shares_share - The number of allocated CPU shares. Applicable when cpu_shares_level is set to custom.
  • memory_limit - Maximum amount of RAM available to a virtual machine (in MB).
  • memory_reservation - Guaranteed minimum amount of RAM available to a virtual machine (in MB).
  • memory_shares_level - RAM allocation level (shares) in the case of contention. Possible values are high, normal, low, and custom.
  • memory_shares_share - The number of allocated RAM shares. Applicable when memory_shares_level is set to custom.
  • disk_io_limit - Maximum I/O utilization by a virtual machine (in I/O operations per second).
  • disk_io_reservation - Guaranteed minimum amount of disk resources available to a virtual machine (in I/O operations per second).
  • disk_io_shares_level - I/O allocation level (shares) in the case of contention. Possible values are high, normal, low, and custom.
  • disk_io_shares_share - The number of allocated I/O shares. Applicable when disk_io_shares_level is set to custom.
  • vif_limit - Maximum network bandwidth available to a virtual network adapter (in Mbps).
  • vif_reservation - Guaranteed minimum network bandwidth available to a virtual network adapter (in Mbps).
  • vif_shares_level - Network bandwidth allocation level (shares) in the case of contention. Possible values are high, normal, low, and custom.
  • vif_shares_share - The number of allocated network bandwidth shares. Applicable when vif_shares_level is set to custom.

3.4. Manage Host Aggregates

A single Compute deployment can be partitioned into logical groups for performance or administrative purposes. OpenStack uses the following terms:

  • Host aggregates - A host aggregate creates logical units in a OpenStack deployment by grouping together hosts. Aggregates are assigned Compute hosts and associated metadata; a host can be in more than one host aggregate. Only administrators can see or create host aggregates.

    An aggregate’s metadata is commonly used to provide information for use with the Compute scheduler (for example, limiting specific flavors or images to a subset of hosts). Metadata specified in a host aggregate will limit the use of that host to any instance that has the same metadata specified in its flavor.

    Administrators can use host aggregates to handle load balancing, enforce physical isolation (or redundancy), group servers with common attributes, or separate out classes of hardware. When you create an aggregate, a zone name must be specified, and it is this name which is presented to the end user.

  • Availability zones - An availability zone is the end-user view of a host aggregate. An end user cannot view which hosts make up the zone, nor see the zone’s metadata; the user can only see the zone’s name.

    End users can be directed to use specific zones which have been configured with certain capabilities or within certain areas.

3.4.1. Enable Host Aggregate Scheduling

By default, host-aggregate metadata is not used to filter instance usage; you must update the Compute scheduler’s configuration to enable metadata usage:

  1. Edit the /etc/nova/nova.conf file (you must have either root or nova user permissions).
  2. Ensure that the scheduler_default_filters parameter contains:

    • AggregateInstanceExtraSpecsFilter for host aggregate metadata. For example:

      scheduler_default_filters=AggregateInstanceExtraSpecsFilter,RetryFilter,RamFilter,ComputeFilter,ComputeCapabilitiesFilter,ImagePropertiesFilter,CoreFilter
    • AvailabilityZoneFilter for availability zone host specification when launching an instance. For example:

      scheduler_default_filters=AvailabilityZoneFilter,RetryFilter,RamFilter,ComputeFilter,ComputeCapabilitiesFilter,ImagePropertiesFilter,CoreFilter
  3. Save the configuration file.

3.4.2. View Availability Zones or Host Aggregates

As an admin user in the dashboard, select Admin > System > Host Aggregates. All currently defined aggregates are listed in the Host Aggregates section; all zones are in the Availability Zones section.

3.4.3. Add a Host Aggregate

  1. As an admin user in the dashboard, select Admin > System > Host Aggregates. All currently defined aggregates are listed in the Host Aggregates section.
  2. Click Create Host Aggregate.
  3. Add a name for the aggregate in the Name field, and a name by which the end user should see it in the Availability Zone field.
  4. Click Manage Hosts within Aggregate.
  5. Select a host for use by clicking its + icon.
  6. Click Create Host Aggregate.

3.4.4. Update a Host Aggregate

  1. As an admin user in the dashboard, select Admin > System > Host Aggregates. All currently defined aggregates are listed in the Host Aggregates section.
  2. To update the instance’s Name or Availability zone:

    • Click the aggregate’s Edit Host Aggregate button.
    • Update the Name or Availability Zone field, and click Save.
  3. To update the instance’s Assigned hosts:

    • Click the aggregate’s arrow icon under Actions.
    • Click Manage Hosts.
    • Change a host’s assignment by clicking its + or - icon.
    • When finished, click Save.
  4. To update the instance’s Metatdata:

    • Click the aggregate’s arrow icon under Actions.
    • Click the Update Metadata button. All current values are listed on the right-hand side under Existing Metadata.
    • Under Available Metadata, click on the Other field, and specify the key you want to add. Use predefined keys (see Table 3.6, “Host Aggregate Metadata”) or add your own (which will only be valid if exactly the same key is set in an instance’s flavor).
    • Click the + button; you can now view the new key under Existing Metadata.

      Note

      Remove a key by clicking its - icon.

    • Click Save.

      Table 3.6. Host Aggregate Metadata

      KeyDescription

      cpu_allocation_ratio

      Sets allocation ratio of virtual CPU to physical CPU. Depends on the AggregateCoreFilter filter being set for the Compute scheduler.

      disk_allocation_ratio

      Sets allocation ratio of Virtual disk to physical disk. Depends on the AggregateDiskFilter filter being set for the Compute scheduler.

      filter_tenant_id

      If specified, the aggregate only hosts this tenant (project). Depends on the AggregateMultiTenancyIsolation filter being set for the Compute scheduler.

      ram_allocation_ratio

      Sets allocation ratio of virtual RAM to physical RAM. Depends on the AggregateRamFilter filter being set for the Compute scheduler.

3.4.5. Delete a Host Aggregate

  1. As an admin user in the dashboard, select Admin > System > Host Aggregates. All currently defined aggregates are listed in the Host Aggregates section.
  2. Remove all assigned hosts from the aggregate:

    1. Click the aggregate’s arrow icon under Actions.
    2. Click Manage Hosts.
    3. Remove all hosts by clicking their - icon.
    4. When finished, click Save.
  3. Click the aggregate’s arrow icon under Actions.
  4. Click Delete Host Aggregate in this and the next dialog screen.

3.5. Schedule Hosts and Cells

The Compute scheduling service determines on which cell or host (or host aggregate), an instance will be placed. As an administrator, you can influence where the scheduler will place an instance. For example, you might want to limit scheduling to hosts in a certain group or with the right RAM.

You can configure the following components:

  • Filters - Determine the initial set of hosts on which an instance might be placed (see Section 3.5.1, “Configure Scheduling Filters”).
  • Weights - When filtering is complete, the resulting set of hosts are prioritized using the weighting system. The highest weight has the highest priority (see Section 3.5.2, “Configure Scheduling Weights”).
  • Scheduler service - There are a number of configuration options in the /etc/nova/nova.conf file (on the scheduler host), which determine how the scheduler executes its tasks, and handles weights and filters. There is both a host and a cell scheduler. For a list of these options, see the Configuration Reference guide.

In the following diagram, both host 1 and 3 are eligible after filtering. Host 1 has the highest weight and therefore has the highest priority for scheduling.

Scheduling Hosts

3.5.1. Configure Scheduling Filters

You define which filters you would like the scheduler to use in the scheduler_default_filters option (/etc/nova/nova.conf file; you must have either root or nova user permissions). Filters can be added or removed.

By default, the following filters are configured to run in the scheduler:

scheduler_default_filters=RetryFilter,AvailabilityZoneFilter,RamFilter,ComputeFilter,ComputeCapabilitiesFilter,ImagePropertiesFilter,ServerGroupAntiAffinityFilter,ServerGroupAffinityFilter

Some filters use information in parameters passed to the instance in:

All available filters are listed in the following table.

Table 3.7. Scheduling Filters

FilterDescription

AggregateCoreFilter

Uses the host-aggregate metadata key cpu_allocation_ratio to filter out hosts exceeding the over-commit ratio (virtual CPU to physical CPU allocation ratio); only valid if a host aggregate is specified for the instance.

 

If this ratio is not set, the filter uses the cpu_allocation_ratio value in the /etc/nova/nova.conf file. The default value is 16.0 (16 virtual CPU can be allocated per physical CPU).

AggregateDiskFilter

Uses the host-aggregate metadata key disk_allocation_ratio to filter out hosts exceeding the over-commit ratio (virtual disk to physical disk allocation ratio); only valid if a host aggregate is specified for the instance.

 

If this ratio is not set, the filter uses the disk_allocation_ratio value in the /etc/nova/nova.conf file. The default value is 1.0 (one virtual disk can be allocated for each physical disk).

AggregateImagePropertiesIsolation

Only passes hosts in host aggregates whose metadata matches the instance’s image metadata; only valid if a host aggregate is specified for the instance. For more information, see Section 1.2.1, “Create an Image”.

AggregateInstanceExtraSpecsFilter

Metadata in the host aggregate must match the host’s flavor metadata. For more information, see Section 3.3.4, “Update Flavor Metadata”.

AggregateMultiTenancyIsolation

A host with the specified filter_tenant_id can only contain instances from that tenant (project).

Note

The tenant can still place instances on other hosts.

AggregateRamFilter

Uses the host-aggregate metadata key ram_allocation_ratio to filter out hosts exceeding the over commit ratio (virtual RAM to physical RAM allocation ratio); only valid if a host aggregate is specified for the instance.

 

If this ratio is not set, the filter uses the ram_allocation_ratio value in the /etc/nova/nova.conf file. The default value is 1.5 (1.5 RAM can be allocated for each physical RAM).

AllHostsFilter

Passes all available hosts (however, does not disable other filters).

AvailabilityZoneFilter

Filters using the instance’s specified availability zone.

ComputeCapabilitiesFilter

Ensures Compute metadata is read correctly. Anything before the : is read as a namespace. For example, quota:cpu_period uses quota as the namespace and cpu_period as the key.

ComputeFilter

Passes only hosts that are operational and enabled.

CoreFilter

Uses the cpu_allocation_ratio in the /etc/nova/nova.conf file to filter out hosts exceeding the over commit ratio(virtual CPU to physical CPU allocation ratio). The default value is 16.0 (16 virtual CPU can be allocated per physical CPU).

DifferentHostFilter

Enables an instance to build on a host that is different from one or more specified hosts. Specify different hosts using the nova boot option --different_host option.

DiskFilter

Uses disk_allocation_ratio in the /etc/nova/nova.conf file to filter out hosts exceeding the over commit ratio(virtual disk to physical disk allocation ratio). The default value is 1.0 (one virtual disk can be allocated for each physical disk).

ImagePropertiesFilter

Only passes hosts that match the instance’s image properties. For more information, see Section 1.2.1, “Create an Image”.

IsolatedHostsFilter

Passes only isolated hosts running isolated images that are specified in the /etc/nova/nova.conf file using isolated_hosts and isolated_images (comma-separated values).

JsonFilter

Recognises and uses an instance’s custom JSON filters:

  • Valid operators are: =, <, >, in, ⇐, >=, not, or, and
  • Recognised variables are: $free_ram_mb, $free_disk_mb, $total_usable_ram_mb, $vcpus_total, $vcpus_used
 

The filter is specfied as a query hint in the nova boot command. For example:

--hint query='['>=', '$free_disk_mb', 200 * 1024]'

MetricFilter

Filters out hosts with unavailable metrics.

NUMATopologyFilter

Filters out hosts based on its NUMA topology; if the instance has no topology defined, any host can be used. The filter tries to match the exact NUMA topology of the instance to those of the host (it does not attempt to pack the instance onto the host). The filter also looks at the standard over-subscription limits for each NUMA node, and provides limits to the compute host accordingly.

RamFilter

Uses ram_allocation_ratio in the /etc/nova/nova.conf file to filter out hosts exceeding the over commit ratio (virtual RAM to physical RAM allocation ratio). The default value is 1.5 (1.5 RAM can be allocated for each physical RAM).

RetryFilter

Filters out hosts that have failed a scheduling attempt; valid if scheduler_max_attempts is greater than zero (by default,scheduler_max_attempts=3).

SameHostFilter

Passes one or more specified hosts; specify hosts for the instance using the --hint same_host option for nova boot.

ServerGroupAffinityFilter

Only passes hosts for a specific server group:

  • Give the server group the affinity policy (nova server-group-create --policy affinity groupName).
  • Build the instance with that group (nova boot option --hint group=UUID)

ServerGroupAntiAffinityFilter

Only passes hosts in a server group that do not already host an instance:

  • Give the server group the anti-affinity policy (nova server-group-create --policy anti-affinity groupName).
  • Build the instance with that group (nova boot option --hint group=UUID).

SimpleCIDRAffinityFilter

Only passes hosts on the specified IP subnet range specified by the instance’s cidr and build_new_host_ip hints. Example:

--hint build_near_host_ip=192.0.2.0 --hint cidr=/24

3.5.2. Configure Scheduling Weights

Both cells and hosts can be weighted for scheduling; the host or cell with the largest weight (after filtering) is selected. All weighers are given a multiplier that is applied after normalising the node’s weight. A node’s weight is calculated as:

w1_multiplier * norm(w1) + w2_multiplier * norm(w2) + ...

You can configure weight options in the scheduler host’s /etc/nova/nova.conf file (must have either root or nova user permissions).

3.5.2.1. Configure Weight Options for Hosts

You can define the host weighers you would like the scheduler to use in the [DEFAULT] scheduler_weight_classes option. Valid weighers are:

  • nova.scheduler.weights.ram - Weighs the host’s available RAM.
  • nova.scheduler.weights.metrics - Weighs the host’s metrics.
  • nova.scheduler.weights.affinity - Weighs the host’s proximity to other hosts in the given server group.
  • nova.scheduler.weights.all_weighers - Uses all host weighers (default).

Table 3.8. Host Weight Options

WeigherOptionDescription

All

[DEFAULT] scheduler_host_subset_size

Defines the subset size from which a host is selected (integer); must be at least 1. A value of 1 selects the first host returned by the weighing functions. Any value less than 1 is ignored and 1 is used instead (integer value).

affinity

[default] soft_affinity_weight_multiplier

Used for weighing hosts for group soft-affinity. Should be a positive floating-point number, because a negative value results in the opposite behavior, which is normally controlled by soft_anti_affinity_weight_multiplier.

affinity

[default] soft_anti_affinity_weight_multiplier

Used for weighing hosts for group soft-anti-affinity. Should be a positive floating-point number, because a negative value results in the opposite behavior, which is normally controlled by soft_affinity_weight_multiplier.

metrics

[metrics] required

Specifies how to handle metrics in [metrics] weight_setting that are unavailable:

  • True- Metrics are required; if unavailable, an exception is raised. To avoid the exception, use the MetricFilter filter in the scheduler_default_filters option.
  • False - The unavailable metric is treated as a negative factor in the weighing process; the returned value is set by weight_of_unavailable.

metrics

[metrics] weight_of_unavailable

Used as the weight if any metric in [metrics] weight_setting is unavailable; valid if required=False.

metrics

[metrics] weight_multiplier

Mulitplier used for weighing metrics. By default, weight_multiplier=1.0 and spreads instances across possible hosts. If this value is negative, the host with lower metrics is prioritized, and instances are stacked in hosts.

metrics

[metrics] weight_setting

Specifies metrics and the ratio with which they are weighed; use a comma-separated list of metric=ratio pairs. Valid metric names are:

  • cpu.frequency - Current CPU frequency
  • cpu.user.time - CPU user mode time
  • cpu.kernel.time - CPU kernel time
  • cpu.idle.time - CPU idle time
  • cpu.iowait.time - CPU I/O wait time
  • cpu.user.percent - CPU user mode percentage
  • cpu.kernel.percent - CPU kernel percentage
  • cpu.idle.percent - CPU idle percentage
  • cpu.iowait.percent - CPU I/O wait percentage
  • cpu.percent - Generic CPU utilization

Example: weight_setting=cpu.user.time=1.0

ram

[DEFAULT] ram_weight_multiplier

Multiplier for RAM (floating point). By default, ram_weight_multiplier=1.0 and spreads instances across possible hosts. If this value is negative, the host with less RAM is prioritized, and instances are stacked in hosts.

3.5.2.2. Configure Weight Options for Cells

You define which cell weighers you would like the scheduler to use in the [cells] scheduler_weight_classes option (/etc/nova/nova.conf file; you must have either root or nova user permissions).

Note

The use of cells is available in this release as a Technology Preview, and therefore is not fully supported by Red Hat. It should only be used for testing, and should not be deployed in a production environment. For more information about Technology Preview features, see Scope of Coverage Details.

Valid weighers are:

  • nova.cells.weights.all_weighers - Uses all cell weighers(default).
  • nova.cells.weights.mute_child - Weighs whether a child cell has not sent capacity or capability updates for some time.
  • nova.cells.weights.ram_by_instance_type - Weighs the cell’s available RAM.
  • nova.cells.weights.weight_offset - Evaluates a cell’s weight offset.

    Note

    A cell’s weight offset is specified using --woffset `in the `nova-manage cell create command.

Table 3.9. Cell Weight Options

WeighersOptionDescription

mute_child

[cells] mute_weight_multiplier

Multiplier for hosts which have been silent for some time (negative floating point). By default, this value is -10.0.

mute_child

[cells] mute_weight_value

Weight value given to silent hosts (positive floating point). By default, this value is 1000.0.

ram_by_instance_type

[cells] ram_weight_multiplier

Multiplier for weighing RAM (floating point). By default, this value is 1.0, and spreads instances across possible cells. If this value is negative, the cell with fewer RAM is prioritized, and instances are stacked in cells.

weight_offset

[cells] offset_weight_multiplier

Multiplier for weighing cells (floating point). Enables the instance to specify a preferred cell (floating point) by setting its weight offset to 999999999999999 (highest weight is prioritized). By default, this value is 1.0.

3.6. Evacuate Instances

If you want to move an instance from a dead or shut-down compute node to a new host server in the same environment (for example, because the server needs to be swapped out), you can evacuate it using nova evacuate.

  • An evacuation is only useful if the instance disks are on shared storage or if the instance disks are Block Storage volumes. Otherwise, the disks will not be accessible and cannot be accessed by the new compute node.
  • An instance can only be evacuated from a server if the server is shut down; if the server is not shut down, the evacuate command will fail.
Note

If you have a functioning compute node, and you want to:

  • Make a static copy (not running) of an instance for backup purposes or to copy the instance to a different environment, make a snapshot using nova image-create (see Migrate a Static Instance).
  • Move an instance in a static state (not running) to a host in the same environment (shared storage not needed), migrate it using nova migrate (see Migrate a Static Instance).
  • Move an instance in a live state (running) to a host in the same environment, migrate it using nova live-migration (see Migrate a Live (running) Instance).

3.6.1. Evacuate One Instance

  1. Evacuate an instance using:

    # nova evacuate [--password pass] [--on-shared-storage] instance_name [target_host]

    Where:

    • --password - Admin password to set for the evacuated instance (cannot be used if --on-shared-storage is specified). If a password is not specified, a random password is generated and output when evacuation is complete.
    • --on-shared-storage - Indicates that all instance files are on shared storage.
    • instance_name - Name of the instance to be evacuated.
    • target_host - Host to which the instance is evacuated; if you do not specify the host, the Compute scheduler selects one for you. You can find possible hosts using:

      # nova host-list | grep compute

      For example:

      # nova evacuate myDemoInstance Compute2_OnEL7.myDomain

3.6.2. Evacuate All Instances

  1. Evacuate all instances on a specified host using:

    # nova host-evacuate instance_name [--target target_host] [--on-shared-storage] source_host

    Where:

    • --target - Host to which the instance is evacuated; if you do not specify the host, the Compute scheduler selects one for you. You can find possible hosts using:

      # nova host-list | grep compute
    • --on-shared-storage - Indicates that all instance files are on shared storage.
    • source_host - Name of the host to be evacuated.

      For example:

      # nova host-evacuate --target Compute2_OnEL7.localdomain myDemoHost.localdomain

3.6.3. Configure Shared Storage

If you are using shared storage, this procedure exports the instances directory for the Compute service to the two nodes, and ensures the nodes have access. The directory path is set in the state_path and instances_path parameters in the /etc/nova/nova.conf file. This procedure uses the default value, which is /var/lib/nova/instances. Only users with root access can set up shared storage.

  1. On the controller host:

    1. Ensure the /var/lib/nova/instances directory has read-write access by the Compute service user (this user must be the same across controller and nodes). For example:

      drwxr-xr-x.  9 nova nova 4096 Nov  5 20:37 instances
    2. Add the following lines to the /etc/exports file; switch out node1_IP and node2_IP for the IP addresses of the two compute nodes:

      /var/lib/nova/instances (rw,sync,fsid=0,no_root_squash)
      /var/lib/nova/instances (rw,sync,fsid=0,no_root_squash)
    3. Export the /var/lib/nova/instances directory to the compute nodes.

      # exportfs -avr
    4. Restart the NFS server:

      # systemctl restart nfs-server
  2. On each compute node:

    1. Ensure the /var/lib/nova/instances directory exists locally.
    2. Add the following line to the /etc/fstab file:

      :/var/lib/nova/instances /var/lib/nova/instances nfs4 defaults 0 0
    3. Mount the controller’s instance directory (all devices listed in /etc/fstab ):

      # mount -a -v
    4. Ensure qemu can access the directory’s images:

      # ls -ld /var/lib/nova/instances
      drwxr-xr-x. 9 nova nova 4096 Nov  5 20:37 /var/lib/nova/instances
    5. Ensure that the node can see the instances directory with:

      drwxr-xr-x. 9 nova nova 4096 Nov  5 20:37 /var/lib/nova/instances
Note

You can also run the following to view all mounted devices:

# df -k

3.7. Manage Instance Snapshots

An instance snapshot allows you to create a new image from an instance. This is very convenient for upgrading base images or for taking a published image and customizing it for local use.

The difference between an image that you upload directly to the Image Service and an image that you create by snapshot is that an image created by snapshot has additional properties in the Image Service database. These properties are found in the image_properties table and include the following parameters:

Table 3.10. Snapshot Options

NameValue

image_type

snapshot

instance_uuid

<uuid of instance that was snapshotted>

base_image_ref

<uuid of original image of instance that was snapshotted>

image_location

snapshot

Snapshots allow you to create new instances based on that snapshot, and potentially restore an instance to that state. Moreover, this can be performed while the instance is running.

By default, a snapshot is accessible to the users and projects that were selected while launching an instance that the snapshot is based on.

3.7.1. Create an Instance Snapshot

Note

If you intend to use an instance snapshot as a template to create new instances, you must ensure that the disk state is consistent. Before you create a snapshot, set the snapshot image metadata property os_require_quiesce=yes. For example,

$ glance image-update IMAGE_ID --property os_require_quiesce=yes

For this to work, the guest should have the qemu-guest-agent package installed, and the image should be created with the metadata property parameter hw_qemu_guest_agent=yes set. For example,

$ glance image-create --name NAME \
--disk-format raw \
--container-format bare \
--file FILE_NAME \
--is-public True \
--property hw_qemu_guest_agent=yes \
--progress

If you unconditionally enable the hw_qemu_guest_agent=yes parameter, then you are adding another device to the guest. This consumes a PCI slot, and will limit the number of other devices you can allocate to the guest. It also causes Windows guests to display a warning message about an unknown hardware device.

For these reasons, setting the hw_qemu_guest_agent=yes parameter is optional, and the parameter should be used for only those images that require the QEMU guest agent.

  1. In the dashboard, select Project > Compute > Instances.
  2. Select the instance from which you want to create a snapshot.
  3. In the Actions column, click Create Snapshot.
  4. In the Create Snapshot dialog, enter a name for the snapshot and click Create Snapshot.

    The Images category now shows the instance snapshot.

To launch an instance from a snapshot, select the snapshot and click Launch.

3.7.2. Manage a Snapshot

  1. In the dashboard, select Project > Images.
  2. All snapshots you created, appear under the Project option.
  3. For every snapshot you create, you can perform the following functions, using the dropdown list:

    1. Use the Create Volume option to create a volume and entering the values for volume name, description, image source, volume type, size and availability zone. For more information, see Create a Volume in the Storage Guide.
    2. Use the Edit Image option to update the snapshot image by updating the values for name, description, Kernel ID, Ramdisk ID, Architecture, Format, Minimum Disk (GB), Minimum RAM (MB), public or private. For more information, see Section 1.2.3, “Update an Image”.
    3. Use the Delete Image option to delete the snapshot.

3.7.3. Rebuild an Instance to a State in a Snapshot

In an event that you delete an instance on which a snapshot is based, the snapshot still stores the instance ID. You can check this information using the nova image-list command and use the snapshot to restore the instance.

  1. In the dashboard, select Project > Compute > Images.
  2. Select the snapshot from which you want to restore the instance.
  3. In the Actions column, click Launch Instance.
  4. In the Launch Instance dialog, enter a name and the other details for the instance and click Launch.

For more information on launching an instance, see Section 3.1.2, “Create an Instance”.

3.7.4. Consistent Snapshots

Previously, file systems had to be quiesced manually (fsfreeze) before taking a snapshot of active instances for consistent backups.

Compute’s libvirt driver automatically requests the QEMU Guest Agent to freeze the file systems (and applications if fsfreeze-hook is installed) during an image snapshot. Support for quiescing file systems enables scheduled, automatic snapshots at the block device level.

This feature is only valid if the QEMU Guest Agent is installed (qemu-ga) and the image metadata enables the agent (hw_qemu_guest_agent=yes)

Note

Snapshots should not be considered a substitute for an actual system backup.

3.8. Use Rescue Mode for Instances

Compute has a method to reboot a virtual machine in rescue mode. Rescue mode provides a mechanism for access when the virtual machine image renders the instance inaccessible. A rescue virtual machine allows a user to fix their virtual machine by accessing the instance with a new root password. This feature is useful if an instance’s filesystem is corrupted. By default, rescue mode starts an instance from the initial image attaching the current boot disk as a secondary one.

3.8.1. Preparing an Image for a Rescue Mode Instance

Due to the fact that both the boot disk and the disk for rescue mode have same UUID, sometimes the virtual machine can be booted from the boot disk instead of the disk for rescue mode.

To avoid this issue, you should create a new image as rescue image based on the procedure in Section 1.2.1, “Create an Image”:

Note

The rescue image is stored in glance and configured in the nova.conf as a default, or you can select when you do the rescue.

3.8.1.1. Rescue Image if Using ext4 Filesystem

When the base image uses ext4 filesystem, you can create a rescue image from it using the following procedure:

  1. Change the UUID to a random value using the tune2fs command:

    # tune2fs -U random /dev/DEVICE_NODE

    Here DEVICE_NODE is the root device node (for example, sda, vda, and so on).

  2. Verify the details of the filesystem, including the new UUID:

    # tune2fs -l
  3. Update the /etc/fstab to use the new UUID. You may need to repeat this for any additional partitions you have, that are mounted in the fstab by UUID.
  4. Update the /boot/grub2/grub.conf file and update the UUID parameter with the new UUID of the root disk.
  5. Shut down and use this image as your rescue image. This will cause the rescue image to have a new random UUID that will not conflict with the instance that you are rescuing.
Note

The XFS filesystem cannot change the UUID of the root device on the running virtual machine. Reboot the virtual machine until the virtual machine is launched from the disk for rescue mode.

3.8.2. Adding the Rescue Image to the OpenStack Image Service

When you have completed modifying the UUID of your image, use the following commands to add the generated rescue image to the OpenStack Image service:

  1. Add the rescue image to the Image service:

    # glance image-create --name IMAGE_NAME --disk-format qcow2 \
      --container-format bare --is-public True --file IMAGE_PATH

    Here IMAGE_NAME is the name of the image, IMAGE_PATH is the location of the image.

  2. Use the image-list command to obtain the IMAGE_ID required for launching an instace in the rescue mode.

    # glance image-list

You can also upload an image using the OpenStack Dashboard, see Section 1.2.2, “Upload an Image”.

3.8.3. Launching an Instance in Rescue Mode

  1. Since you need to rescue an instance with a specific image, rather than the default one, use the --rescue_image_ref parameter:

    # nova rescue --rescue_image_ref IMAGE_ID VIRTUAL_MACHINE_ID

    Here IMAGE_ID is the ID of the image you want to use and VIRTUAL_MACHINE_ID is ID of a virtual machine that you want to rescue.

    Note

    The nova rescue command allows an instance to perform a soft shut down. This allows the guest operating system to perform a controlled shutdown before the instance is powered off. The shut down behavior is configured by the shutdown_timeout parameter that can be set in the nova.conf file. The value stands for the overall period (in seconds) a guest operation system is allowed to complete the shutdown. The default timeout is 60 seconds.

    The timeout value can be overridden on a per image basis by means of os_shutdown_timeout that is an image metadata setting allowing different types of operating systems to specify how much time they need to shut down cleanly.

  2. Reboot the virtual machine.
  3. Confirm the status of the virtual machine is RESCUE on the controller node by using nova list command or by using dashboard.
  4. Log in to the new virtual machine dashboard by using the password for rescue mode.

You can now make the necessary changes to your instance to fix any issues.

3.8.4. Unrescuing an Instance

You can unrescue the fixed instance to restart it from the boot disk.

  1. Execute the following commands on the controller node.

    # nova unrescue VIRTUAL_MACHINE_ID

    Here VIRTUAL_MACHINE_ID is ID of a virtual machine that you want to unrescue.

The status of your instance returns to ACTIVE once the unrescue operation has completed successfully.

3.9. Set a Configuration Drive for Instances

You can use the config-drive parameter to present a read-only drive to your instances. This drive can contain selected files that are then accessible to the instance. The configuration drive is attached to the instance at boot, and is presented to the instance as a partition. Configuration drives are useful when combined with cloud-init (for server bootstrapping), and when you want to pass large files to your instances.

3.9.1. Configuration Drive Options

Set the initial configuration drive options under [DEFAULT] in nova.conf:

  • config_drive_format - sets the format of the drive, and accepts the options iso9660 and vfat. By default, it uses iso9660.
  • force_config_drive=true - this forces the configuration drive to be presented to all instances.
  • mkisofs_cmd=genisoimage - specifies the command to use for ISO file creation. This value must not be changed, as only genisoimage is supported.

3.9.2. Use a Configuration Drive

An instance attaches its configuration drive at boot time. This is enabled by the --config-drive option. For example, this command creates a new instance named test-instance01 and attaches a drive containing a file named /root/user-data.txt:

# nova boot --flavor m1.tiny --config-drive true --file /root/user-data.txt=/root/user-data.txt --image cirros test-instance01

Once the instance has booted, you can log in to it and see a file named /root/user-data.txt.

Note

You can use the configuration drive as a source for cloud-init information. During the initial instance boot, cloud-init can automatically mount the configuration drive and run the setup scripts.

Chapter 4. Configure CPU Pinning with NUMA

This chapter concerns NUMA topology awareness and the configuration of an OpenStack environment on systems supporting this technology. With this setup, virtual machine instances are pinned to dedicated CPU cores, which enables smarter scheduling and therefore improves guest performance.

Tip

Background information about NUMA is available in the following article: What is NUMA and how does it work on Linux ?

The following diagram provides an example of a two-node NUMA system and the way the CPU cores and memory pages are made available:

OpenStack NUMA Topology 39825 0416 ADF
Note

Remote memory available via Interconnect is accessed only if VM1 from NUMA node 0 has a CPU core in NUMA node 1. In this case, the memory of NUMA node 1 will act as local for the third CPU core of VM1 (for example, if VM1 is allocated with CPU 4 in the diagram above), but at the same time, it will act as remote memory for the other CPU cores of the same VM.

For more details on NUMA tuning with libvirt, see the Virtualization Tuning and Optimization Guide.

Warning

At present, it is impossible to migrate an instance which has been configured to use CPU pinning. For more information about this issue, see the following solution: Instance migration fails when using cpu-pinning from a numa-cell and flavor-property "hw:cpu_policy=dedicated".

4.1. Compute Node Configuration

The exact configuration depends on the NUMA topology of your host system; however, you must reserve some CPU cores across all the NUMA nodes for host processes and let the rest of the CPU cores handle your guest virtual machine instances. For example, with eight CPU cores evenly spread across two NUMA nodes, the layout can be illustrated as follows:

Table 4.1. Example of NUMA Topology

 

Node 0

Node 1

Host processes

Core 0

Core 1

Core 4

Core 5

Guest processes

Core 2

Core 3

Core 6

Core 7

Note

The number of cores to reserve for host processes should be determined by observing the performance of the host under typical workloads.

The configuration of the Compute nodes consists of the following steps:

  1. Set the vcpu_pin_set option in the /etc/nova/nova.conf file to the list of CPU cores reserved for guest processes. Using the example above, you would set:

    vcpu_pin_set=2,3,6,7

    The vcpu_pin_set option will also ensure that a cpuset attribute similar to the following will be added to the XML configuration file for libvirt:

    <vcpu placement='static' cpuset='2-3,6-7'>1</vcpu>

    This will pin the guest vCPUs to the listed physical CPU cores and allow the scheduler to see only these cores.

  2. Set the reserved_host_memory_mb option in the same file to the amount of RAM to reserve for host processes. If you want to reserve 512 MB, use:

    reserved_host_memory_mb=512
  3. Restart the Compute service on the Compute nodes by running the following command:

    systemctl restart openstack-nova-compute.service
  4. Ensure that host processes do not run on the CPU cores reserved for guest processes by adding the isolcpus argument to the system’s boot configuration. Use the list of CPU cores reserved for guest processes as a parameter of this argument. Using the topology from the example above, you would run the following command:

    grubby --update-kernel=ALL --args="isolcpus=2,3,6,7"
    Note

    The cpuset option along with the isolcpus kernel argument will ensure that the underlying compute node will not be able to use the corresponding pCPUs for itself. The pCPUs will be dedicated to instances.

  5. Update the boot record for this change to take effect:

    grub2-install /dev/device

    Replace device with the name of the device that contains the boot record, usually sda.

  6. Reboot the system.

4.2. Scheduler Configuration

  1. Edit the /etc/nova/nova.conf file on each system running the OpenStack Compute Scheduler. Find the scheduler_default_filters option, uncomment it if commented out, and add AggregateInstanceExtraSpecFilter and NUMATopologyFilter to the list of filters. The whole line can look like this:

    scheduler_default_filters=RetryFilter,AvailabilityZoneFilter,RamFilter,
    ComputeFilter,ComputeCapabilitiesFilter,ImagePropertiesFilter,CoreFilter,
    NUMATopologyFilter,AggregateInstanceExtraSpecsFilter
  2. Restart the openstack-nova-scheduler service:

    systemctl restart openstack-nova-scheduler.service

4.3. Aggregate and Flavor Configuration

Prepare your OpenStack environment for running virtual machine instances pinned to specific resources by completing the following steps on a system with the Compute command-line interface:

  1. Load the admin credentials:

    source ~/keystonerc_admin
  2. Create an aggregate for the hosts that will receive pinning requests:

    nova aggregate-create name

    Replace name with a suitable name, such as performance or cpu_pinning.

  3. Enable the pinning by editing the metadata for the aggregate:

    nova aggregate-set-metadata 1 pinned=true

    In this command, number 1 matches the ID of the aggregate created in the previous step.

  4. Create an aggregate for other hosts:

    nova aggregate-create name

    Replace name with another suitable name, such as normal.

  5. Edit the metadata for this aggregate accordingly:

    nova aggregate-set-metadata 2 pinned=false

    Here, number 2 is used because it comes after 1, which is the ID of the first aggregate.

  6. Change your existing flavors' specifications to this one:

    for i in $(nova flavor-list | cut -f 2 -d ' ' | grep -o '[0-9]*'); do nova flavor-key $i set "aggregate_instance_extra_specs:pinned"="false"; done
  7. Create a flavor for the hosts that will receive pinning requests:

    nova flavor-create name ID RAM disk vCPUs

    Replace name with an appropriate name, such as m1.small.performance or pinned.small, ID with the identifier for the new flavor (6 if you have five standard flavors, or auto if you want nova to generate a UUID), RAM with the desired amount of RAM in MB, disk with the desired disk size in GB, and vCPUs with the number of virtual CPUs that you want to reserve.

  8. Set the hw:cpu_policy specification of this flavor to dedicated so as to require dedicated resources, which enables CPU pinning, and also the hw:cpu_thread_policy specification to require, which places each vCPU on thread siblings:

    nova flavor-key ID set hw:cpu_policy=dedicated
    nova flavor-key ID set hw:cpu_thread_policy=require

    Replace ID with the ID of the flavor created in the previous step.

    Note

    If the host does not have an SMT architecture or enough CPU cores with free thread siblings, scheduling will fail. If such behavior is undesired, or if your hosts simply do not have an SMT architecture, do not use the hw:cpu_thread_policy specification, or set it to prefer instead of require. The (default) prefer policy ensures that thread siblings are used when available.

  9. Set the aggregate_instance_extra_specs:pinned specification to true so as to ensure that instances based on this flavor have this specification in their aggregate metadata:

    nova flavor-key ID set aggregate_instance_extra_specs:pinned=true

    Again, replace ID with the ID of the flavor.

  10. Add some hosts to the new aggregates:

    nova aggregate-add-host ID_1 host_1

    Replace ID_1 with the ID of the first ("performance"/"pinning") aggregate and host_1 with the host name of the host that you want to add to the aggregate.

    nova aggregate-add-host ID_2 host_2

    Replace ID_2 with the ID of the second ("normal") aggregate and host_2 with the host name of the host that you want to add to it.

You can now boot an instance using the new flavor:

nova boot --image image --flavor flavor server_name

Replace image with a saved VM image name (see nova image-list), flavor with the name of the flavor (m1.small.performance, pinned.small, or any other name that you used), and server_name with the name for the new server.

To verify that the new server has been placed correctly, run the following command and check for OS-EXT-SRV-ATTR:hypervisor_hostname in the output:

nova show server_name

Appendix A. Image Configuration Parameters

The following keys can be used with the property option for both the glance image-update and glance image-create commands.

$ glance image-update IMG-UUID --property architecture=x86_64
Note

Behavior set using image properties overrides behavior set using flavors. For more information, see Section 3.3, “Manage Flavors”.

Table A.1. Property Keys

Specific toKeyDescriptionSupported values

All

architecture

The CPU architecture that must be supported by the hypervisor. For example, x86_64, arm, or ppc64. Run uname -m to get the architecture of a machine. We strongly recommend using the architecture data vocabulary defined by the libosinfo project for this purpose.

  • alpha-DEC 64-bit RISC
  • armv7l-ARM Cortex-A7 MPCore
  • cris-Ethernet, Token Ring, AXis-Code Reduced Instruction Set
  • i686-Intel sixth-generation x86 (P6 micro architecture)
  • ia64-Itanium
  • lm32-Lattice Micro32
  • m68k-Motorola 68000
  • microblaze-Xilinx 32-bit FPGA (Big Endian)
  • microblazeel-Xilinx 32-bit FPGA (Little Endian)
  • mips-MIPS 32-bit RISC (Big Endian)
  • mipsel-MIPS 32-bit RISC (Little Endian)
  • mips64-MIPS 64-bit RISC (Big Endian)
  • mips64el-MIPS 64-bit RISC (Little Endian)
  • openrisc-OpenCores RISC
  • parisc-HP Precision Architecture RISC
  • parisc64-HP Precision Architecture 64-bit RISC
  • ppc-PowerPC 32-bit
  • ppc64-PowerPC 64-bit
  • ppcemb-PowerPC (Embedded 32-bit)
  • s390-IBM Enterprise Systems Architecture/390
  • s390x-S/390 64-bit
  • sh4-SuperH SH-4 (Little Endian)
  • sh4eb-SuperH SH-4 (Big Endian)
  • sparc-Scalable Processor Architecture, 32-bit
  • sparc64-Scalable Processor Architecture, 64-bit
  • unicore32-Microprocessor Research and Development Center RISC Unicore32
  • x86_64-64-bit extension of IA-32
  • xtensa-Tensilica Xtensa configurable microprocessor core
  • xtensaeb-Tensilica Xtensa configurable microprocessor core (Big Endian)

All

hypervisor_type

The hypervisor type.

kvm, vmware

All

instance_uuid

For snapshot images, this is the UUID of the server used to create this image.

Valid server UUID

All

kernel_id

The ID of an image stored in the Image Service that should be used as the kernel when booting an AMI-style image.

Valid image ID

All

os_distro

The common name of the operating system distribution in lowercase (uses the same data vocabulary as the libosinfo project). Specify only a recognized value for this field. Deprecated values are listed to assist you in searching for the recognized value.

  • arch-Arch Linux. Do not use archlinux or org.archlinux
  • centos-Community Enterprise Operating System. Do not use org.centos or CentOS
  • debian-Debian. Do not use Debian or org.debian
  • fedora-Fedora. Do not use Fedora, org.fedora, or org.fedoraproject
  • freebsd-FreeBSD. Do not use org.freebsd, freeBSD, or FreeBSD
  • gentoo-Gentoo Linux. Do not use Gentoo or org.gentoo
  • mandrake-Mandrakelinux (MandrakeSoft) distribution. Do not use mandrakelinux or MandrakeLinux
  • mandriva-Mandriva Linux. Do not use mandrivalinux
  • mes-Mandriva Enterprise Server. Do not use mandrivaent or mandrivaES
  • msdos-Microsoft Disc Operating System. Do not use ms-dos
  • netbsd-NetBSD. Do not use NetBSD or org.netbsd
  • netware-Novell NetWare. Do not use novell or NetWare
  • openbsd-OpenBSD. Do not use OpenBSD or org.openbsd
  • opensolaris-OpenSolaris. Do not use OpenSolaris or org.opensolaris
  • opensuse-openSUSE. Do not use suse, SuSE, or org.opensuse
  • rhel-Red Hat Enterprise Linux. Do not use redhat, RedHat, or com.redhat
  • sled-SUSE Linux Enterprise Desktop. Do not use com.suse
  • ubuntu-Ubuntu. Do not use Ubuntu, com.ubuntu, org.ubuntu, or canonical
  • windows-Microsoft Windows. Do not use com.microsoft.server

All

os_version

The operating system version as specified by the distributor.

Version number (for example, "11.10")

All

ramdisk_id

The ID of image stored in the Image Service that should be used as the ramdisk when booting an AMI-style image.

Valid image ID

All

vm_mode

The virtual machine mode. This represents the host/guest ABI (application binary interface) used for the virtual machine.

hvm-Fully virtualized. This is the mode used by QEMU and KVM.

libvirt API driver

hw_disk_bus

Specifies the type of disk controller to attach disk devices to.

scsi, virtio, ide, or usb.

libvirt API driver

hw_numa_nodes

Number of NUMA nodes to expose to the instance (does not override flavor definition).

Integer. For a detailed example of NUMA-topology definition, see the hw:NUMA_def key in Add Metadata.

libvirt API driver

hw_numa_mempolicy

NUMA memory allocation policy (does not override flavor definition).

strict - Mandatory for the instance’s RAM allocations to come from the NUMA nodes to which it is bound (default if numa_nodes is specified). preferred - The kernel can fall back to using an alternative node. Useful when the 'hw:numa_nodes' parameter is set to '1'.

libvirt API driver

hw_numa_cpus.0

Mapping of vCPUs N-M to NUMA node 0 (does not override flavor definition).

Comma-separated list of integers.

libvirt API driver

hw_numa_cpus.1

Mapping of vCPUs N-M to NUMA node 1 (does not override flavor definition).

Comma-separated list of integers.

libvirt API driver

hw_numa_mem.0

Mapping N GB of RAM to NUMA node 0 (does not override flavor definition).

Integer

libvirt API driver

hw_numa_mem.1

Mapping N GB of RAM to NUMA node 1 (does not override flavor definition).

Integer

libvirt API driver

hw_qemu_guest_agent

Guest agent support. If set to yes, and if qemu-ga is also installed, file systems can be quiesced (frozen) and snapshots created automatically.

yes / no

libvirt API driver

hw_rng_model

Adds a random-number generator device to the image’s instances. The cloud administrator can enable and control device behavior by configuring the instance’s flavor. By default:

  • The generator device is disabled.
  • /dev/random is used as the default entropy source. To specify a physical HW RNG device, use the following option in the nova.conf file: rng_dev_path=/dev/hwrng

virtio, or other supported device.

libvirt API driver

hw_scsi_model

Enables the use of VirtIO SCSI (virtio-scsi) to provide block device access for compute instances; by default, instances use VirtIO Block (virtio-blk). VirtIO SCSI is a para-virtualized SCSI controller device that provides improved scalability and performance, and supports advanced SCSI hardware.

virtio-scsi

libvirt API driver

hw_video_model

The video image driver used.

vga, cirrus, vmvga, xen, or qxl

libvirt API driver

hw_video_ram

Maximum RAM for the video image. Used only if a hw_video:ram_max_mb value has been set in the flavor’s extra_specs and that value is higher than the value set in hw_video_ram.

Integer in MB (for example, '64')

libvirt API driver

hw_watchdog_action

Enables a virtual hardware watchdog device that carries out the specified action if the server hangs. The watchdog uses the i6300esb device (emulating a PCI Intel 6300ESB). If hw_watchdog_action is not specified, the watchdog is disabled.

  • disabled-The device is not attached. Allows the user to disable the watchdog for the image, even if it has been enabled using the image’s flavor. The default value for this parameter is disabled.
  • reset-Forcefully reset the guest.
  • poweroff-Forcefully power off the guest.
  • pause-Pause the guest.
  • none-Only enable the watchdog; do nothing if the server hangs.

libvirt API driver

os_command_line

The kernel command line to be used by the libvirt driver, instead of the default. For Linux Containers (LXC), the value is used as arguments for initialization. This key is valid only for Amazon kernel, ramdisk, or machine images (aki, ari, or ami).

 

libvirt API driver and VMware API driver

hw_vif_model

Specifies the model of virtual network interface device to use.

The valid options depend on the configured hypervisor.

  • KVM and QEMU: e1000, ne2k_pci, pcnet, rtl8139, and virtio.
  • VMware: e1000, e1000e, VirtualE1000, VirtualE1000e, VirtualPCNet32, VirtualSriovEthernetCard, and VirtualVmxnet.
  • Xen: e1000, netfront, ne2k_pci, pcnet, and rtl8139.

VMware API driver

vmware_adaptertype

The virtual SCSI or IDE controller used by the hypervisor.

lsiLogic, busLogic, or ide

VMware API driver

vmware_ostype

A VMware GuestID which describes the operating system installed in the image. This value is passed to the hypervisor when creating a virtual machine. If not specified, the key defaults to otherGuest.

See thinkvirt.com.

VMware API driver

vmware_image_version

Currently unused.

1

XenAPI driver

auto_disk_config

If true, the root partition on the disk is automatically resized before the instance boots. This value is only taken into account by the Compute service when using a Xen-based hypervisor with the XenAPI driver. The Compute service will only attempt to resize if there is a single partition on the image, and only if the partition is in ext3 or ext4 format.

true / false

XenAPI driver

os_type

The operating system installed on the image. The XenAPI driver contains logic that takes different actions depending on the value of the os_type parameter of the image. For example, for os_type=windows images, it creates a FAT32-based swap partition instead of a Linux swap partition, and it limits the injected host name to less than 16 characters.

linux or windows

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