Red Hat Training

A Red Hat training course is available for Red Hat OpenStack Platform

Chapter 3. Overcloud Images

The Red Hat OpenStack Platform director provides images for the Overcloud. The QCOW image in this collection contains a base set of software components that integrate together to form various Overcloud roles, such as Compute, Controller, and storage nodes. In some situations, you might aim to modify certain aspects of the Overcloud image to suit your needs, such installing additional components to nodes.

This document describes a series of actions to use the virt-customize tool to modify an existing Overcloud image to augment an existing Controller node. For example, you can use these procedures to install additional ml2 plugins, Cinder backends, or monitoring agents not shipped with the initial image.


If you modify the Overcloud image to include third-party software and report an issue, Red Hat may request you reproduce the issue using an unmodified image in accordance with our general third-party support policy:

3.1. Obtaining the Overcloud Images

The director requires several disk images for provisioning Overcloud nodes. This includes:

  • A introspection kernel and ramdisk - Used for bare metal system introspection over PXE boot.
  • A deployment kernel and ramdisk - Used for system provisioning and deployment.
  • An Overcloud kernel, ramdisk, and full image - A base Overcloud system that is written to the node’s hard disk.

Obtain these images from the rhosp-director-images and rhosp-director-images-ipa packages:

$ sudo yum install rhosp-director-images rhosp-director-images-ipa

Extract the archives to the images directory on the stack user’s home (/home/stack/images):

$ cd ~/images
$ for i in /usr/share/rhosp-director-images/overcloud-full-latest-11.0.tar /usr/share/rhosp-director-images/ironic-python-agent-latest-11.0.tar; do tar -xvf $i; done

3.2. Initrd: Modifying the Initial Ramdisks

Some situations might require you to modify the initial ramdisk. For example, you might require a certain driver available when you boot the nodes during the introspection or provisioning processes. The following procedure shows how to modify an initial ramdisk. In the context of the Overcloud, this includes either:

  • The introspection ramdisk - ironic-python-agent.initramfs
  • The provisioning ramdisk - overcloud-full.initrd

This procedure adds an additional RPM package to the ironic-python-agent.initramfs ramdisk as an example.

Log in as the root user and create a temporary directory for the ramdisk

# mkdir ~/ipa-tmp
# cd ~/ipa-tmp

Use the skipcpio and `cpio commands to extract the ramdisk to the temporary directory:

# /usr/lib/dracut/skipcpio ~/images/ironic-python-agent.initramfs | zcat | cpio -ivd | pax -r

Install an RPM package to the extracted contents:

# rpm2cpio ~/RPMs/python-proliantutils-2.1.7-1.el7ost.noarch.rpm | pax -r

Recreate the new ramdisk:

# find . 2>/dev/null | cpio --quiet -c -o | gzip -8  > /home/stack/images/ironic-python-agent.initramfs
# chown stack: /home/stack/images/ironic-python-agent.initramfs

Verify the new package now exists in the ramdisk:

# lsinitrd /home/stack/images/ironic-python-agent.initramfs | grep proliant

3.3. QCOW: Installing virt-customize to the director

The libguestfs-tools package contains the virt-customize tool. Install the libguestfs-tools from the rhel-7-server-rpms repository:

$ sudo yum install libguestfs-tools

3.4. QCOW: Inspecting the Overcloud Image

You might aim to explore the contents of the overcloud-full.qcow2. Create a virtual machine instance using either the qemu-system-x86_64 command:

$ sudo qemu-system-x86_64 --kernel overcloud-full.vmlinuz --initrd overcloud-full.initrd -m 1024 --append root=/dev/sda --enable-kvm overcloud-full.qcow2

Or using the following boot options in virt-manager:

  • Kernel path: /overcloud-full.vmlinuz
  • initrd path: /overcloud-full.initrd
  • Kernel arguments: root=/dev/sda

3.5. QCOW: Setting the Root Password

Set the password for the root user on image:

$ virt-customize --selinux-relabel -a overcloud-full.qcow2 --root-password password:test
[  0.0] Examining the guest ...
[ 18.0] Setting a random seed
[ 18.0] Setting passwords
[ 19.0] Finishing off

This provides administration-level access for your nodes through the console.

3.6. QCOW: Registering the Image

Register your image temporarily to enable Red Hat repositories relevant to your customizations:

$ virt-customize --selinux-relabel -a overcloud-full.qcow2 --run-command 'subscription-manager register --username=[username] --password=[password]'
[  0.0] Examining the guest ...
[ 10.0] Setting a random seed
[ 10.0] Running: subscription-manager register --username=[username] --password=[password]
[ 24.0] Finishing off

Make sure to replace the [username] and [password] with your Red Hat customer account details. This runs the following command on the image:

subscription-manager register --username=[username] --password=[password]

This registers your Overcloud image to the Red Hat Content Delivery Network:

3.7. QCOW: Attaching a Subscription and Enabling Red Hat Repositories

Find a list of pool ID from your account’s subscriptions:

$ sudo subscription-manager list

Choose a subscription pool ID and attach it to the image:

$ virt-customize --selinux-relabel -a overcloud-full.qcow2 --run-command 'subscription-manager attach --pool [subscription-pool]'
[  0.0] Examining the guest ...
[ 12.0] Setting a random seed
[ 12.0] Running: subscription-manager attach --pool [subscription-pool]
[ 52.0] Finishing off

Make sure to replace the [subscription-pool] with your chosen subscription pool ID. This runs the following command on the image:

subscription-manager attach --pool [subscription-pool]

This adds the pool to the image, which allows you to enable Red Hat repositories with the following command:

$ subscription-manager repos --enable=[repo-id]

3.8. QCOW: Copying a Custom Repository File

Adding third-party software to the image requires additional repositories. For example, the following is an example repo file that contains configuration to use the OpenDaylight repository content:

$ cat opendaylight.repo

name=OpenDaylight Repository

Copy the repository file on to the image:

$ virt-customize --selinux-relabel -a overcloud-full.qcow2 --upload opendaylight.repo:/etc/yum.repos.d/
[  0.0] Examining the guest ...
[ 12.0] Setting a random seed
[ 12.0] Copying: opendaylight.repo to /etc/yum.repos.d/
[ 13.0] Finishing off

The --copy-in option copies the repository file to /etc/yum.repos.d/ on the Overcloud image.

Important: Red Hat does not offer support for software from non-certified vendors. Check with your Red Hat support representative that the software you aim to install is supported.

3.9. QCOW: Installing RPMs

Use the virt-customize command to install packages to the image:

$ virt-customize --selinux-relabel -a overcloud-full.qcow2 --install opendaylight
[  0.0] Examining the guest ...
[ 11.0] Setting a random seed
[ 11.0] Installing packages: opendaylight
[ 91.0] Finishing off

The --install option allows you to specify a package to install.

3.10. QCOW: Cleaning the Subscription Pool

After installing the necessary packages to customize the image, we now remove our subscriptions and unregister the image:

$ virt-customize --selinux-relabel -a overcloud-full.qcow2 --run-command 'subscription-manager remove --all'
[  0.0] Examining the guest ...
[ 12.0] Setting a random seed
[ 12.0] Running: subscription-manager remove --all
[ 18.0] Finishing off

This removes all subscription pools from the image.

3.11. QCOW: Unregistering the Image

Finally, unregister the image. This is so the Overcloud deployment process can deploy the image to your nodes and register each of them individually.

$ virt-customize --selinux-relabel -a overcloud-full.qcow2 --run-command 'subscription-manager unregister'
[  0.0] Examining the guest ...
[ 11.0] Setting a random seed
[ 11.0] Running: subscription-manager unregister
[ 17.0] Finishing off

3.12. Uploading the Images to the Director

After modifying the image, upload it to the director. Make sure to source the stackrc file so that you can access the director from the command line:

$ source stackrc
$ openstack overcloud image upload --image-path /home/stack/images/

This uploads the following images into the director: bm-deploy-kernel, bm-deploy-ramdisk, overcloud-full, overcloud-full-initrd, and overcloud-full-vmlinuz. These are the images for deployment and the Overcloud. The script also installs the introspection images on the director’s PXE server. View a list of the images in the CLI using the following command:

$ openstack image list
| ID                                   | Name                   |
| 765a46af-4417-4592-91e5-a300ead3faf6 | bm-deploy-ramdisk      |
| 09b40e3d-0382-4925-a356-3a4b4f36b514 | bm-deploy-kernel       |
| ef793cd0-e65c-456a-a675-63cd57610bd5 | overcloud-full         |
| 9a51a6cb-4670-40de-b64b-b70f4dd44152 | overcloud-full-initrd  |
| 4f7e33f4-d617-47c1-b36f-cbe90f132e5d | overcloud-full-vmlinuz |

This list will not show the introspection PXE images (agent.*). The director copies these files to /httpboot.

[stack@host1 ~]$ ls /httpboot -l
total 151636
-rw-r--r--. 1 ironic ironic       269 Sep 19 02:43 boot.ipxe
-rw-r--r--. 1 root   root         252 Sep 10 15:35 inspector.ipxe
-rwxr-xr-x. 1 root   root     5027584 Sep 10 16:32 agent.kernel
-rw-r--r--. 1 root   root   150230861 Sep 10 16:32 agent.ramdisk
drwxr-xr-x. 2 ironic ironic      4096 Sep 19 02:45 pxelinux.cfg