Chapter 4. Images and Storage

This chapter discusses the steps you can follow to manage images and storage in RHEL 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 RHEL 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 we don't normally think of ISO as 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, you require a valid Red Hat Enterprise Linux subscription:

4.1. 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.

4.1.1. Create an Image

This section provides you with the steps to manually create OpenStack-compatible images in .qcow2 format using Red Hat Enterprise Linux 6 and Red Hat Enterprise Linux 7 ISO files.

4.1.1.1. Use a KVM Guest Image With RHEL OpenStack Platform

You can use a ready RHEL KVM guest qcow2 image available at: RHEL 7 KVM Guest Image or RHEL 6.6 KVM Guest 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.
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 want to create custom Red Hat Enterprise Linux images, see Section 4.1.1.2.1, “Create a Red Hat Enterprise Linux 7 Image” or Section 4.1.1.2.2, “Create a Red Hat Enterprise Linux 6 Image”.

4.1.1.2. Create Custom Red Hat Enterprise Linux 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 @virtualization). This installs all packages necessary for creating a guest operating system.
  • Libguestfs tools (run command yum install libguestfs-tools-c). This installs a set of tools for accessing and modifying virtual machine images.
  • A Red Hat Enterprise Linux ISO file (see RHEL 7.0 Binary DVD or RHEL 6.6 Binary DVD ).
  • Text editor, if you want to change the kickstart files.
Note
In the following procedures, all commands with the [user@host]# prompt should be run on your host machine.
4.1.1.2.1. Create a Red Hat Enterprise Linux 7 Image
This section provides you with the steps to manually create an OpenStack-compatible image in .qcow2 format using a Red Hat Enterprise Linux 7 ISO file.
  1. Start the installation using virt-install: 
    [user@host]# qemu-img create -f qcow2 rhel7.qcow2 8G
[user@host]# virt-install --virt-type kvm --name rhel7 --ram 2048 \
--cdrom /tmp/rhel-server-7.0-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 following command to view the console: 
    [user@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 7.0 option.
    2. Choose the appropriate Language and Keyboard options.
    3. When prompted about which type of devices your installation uses, choose Auto-detected installation media.
    4. When prompted about which type of installation destination, choose Local Standard Disks.
      For other storage options, choose Automatically configure partitioning.
    5. For software selection, choose Minimal Install.
    6. For network and hostname, choose eth0 for network and choose a hostname for your device. The default hostname is localhost.localdomain.
    7. Choose the root password.
      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: 
    # subscription-manager register
    1. Enter your Customer Portal user name and password when prompted: 
      Username: admin@example.com
Password:
    2. Find entitlement pools containing the channel: 
      # subscription-manager list --available | grep -A8 "Red Hat Enterprise Linux Server"
    3. Use the pool identifiers located in the previous step to attach the Red Hat Enterprise Linux Server entitlement to the system: 
      # subscription-manager attach --pool=pool_id
    4. Enable the required channel: 
      # subscription-manager repos --enable=rhel-7-server-rpms
      For RHEL OpenStack Platform 6, the required channels are rhel-7-server-openstack-6.0-rpms and rhel-7-server-rh-common-rpms.
      Note
      For more information, see Software Repository Configuration
  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. 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 following 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 to create instances without issues: 
    [user@host]# virt-sysprep -d rhel7
  15. Reduce the size of the image using the virt-sparsify command. This command converts any free space within the disk image back to free space within the host: 
    [user@host]# virt-sparsify --compress 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 Section 4.1.2, “Upload an Image”.
4.1.1.2.2. Create a Red Hat Enterprise Linux 6 Image
This section provides you with the steps to manually create an OpenStack-compatible image in .qcow2 format using a Red Hat Enterprise Linux 6 ISO file.
  1. Start the installation using virt-install: 
    [user@host]# qemu-img create -f qcow2 rhel6.qcow2 4G
[user@host]# virt-install --connect=qemu:///system --network=bridge:virbr0 \
--name=rhel6.6 --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-6.6-x86_64-dvd.iso
    This launches an instance and starts the installation process.
    Note
    If the instance does not launch automatically, run the following command to view the console: 
    [user@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.
      Step through the installation prompts. Accept the defaults.
      The installation checks for disc and performs a Media Check. When the check is a Success, it ejects the disc.
    2. Choose the appropriate Language and Keyboard options.
    3. When prompted about which type of devices your installation uses, choose Basic Storage Devices.
    4. Choose a hostname for your device. The default hostname is localhost.localdomain.
    5. Set timezone and root password.
    6. Based on the space on the disk, choose the type of installation.
    7. Choose the Basic Server install, which installs an SSH server.
      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: 
    # subscription-manager register
    1. Enter your Customer Portal user name and password when prompted: 
      Username: admin@example.com
Password:
    2. Find entitlement pools containing the channel: 
      # subscription-manager list --available | grep -A8 "Red Hat Enterprise Linux Server"
    3. Use the pool identifiers located in the previous step to attach the Red Hat Enterprise Linux Server entitlement to the system: 
      # subscription-manager attach --pool=pool_id
    4. Enable the required channel: 
      # subscription-manager repos --enable=rhel-6-server-rpms
      For RHEL OpenStack Platform 6, the required channels are rhel-7-server-openstack-6.0-rpms and rhel-6-server-rh-common-rpms.
      Note
      For more information, see Software Repository Configuration
  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 /etc/udev/rules.d/75-persistent-net-generator.rules file. 
    # 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 to create instances without issues: 
    [user@host]# virt-sysprep -d rhel6.6
  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: 
    [user@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 Section 4.1.2, “Upload an Image”.

4.1.2. 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.
    Field Notes
    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.
Note
You can also use the glance image-create command with the property option to create an image. More values are available on the commmand line. For a complete listing, see Appendix A, Image Configuration Parameters.

4.1.3. Update an Image

  1. In the dashboard, select Project > Compute > Images.
  2. Click Edit.
    Note
    The Edit option is available only when you login as an admin user. When you login 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 dropdown 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 commmand line; for a complete listing, see Appendix A, Image Configuration Parameters.

4.1.4. Delete an Image

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