Create a custom OpenStack image with Packer

Objective

This guide will show you how to create a Packer configuration file to create your own OpenStack image.

Requirements

You'll need an OVHcloud Public Cloud project and a terminal.

OVHcloud Console Access

• Direct link: Projects
• Navigation path: Public Cloud > Select your project

Install Packer

Packer can be downloaded from the official website (currently here ) and you'll need to unzip it.

For Linux 64bits

wget https://releases.hashicorp.com/packer/1.11.2/packer_1.11.2_linux_amd64.zip
unzip packer_1.11.2_linux_amd64.zip

Install the OpenStack plugin for Packer

packer plugins install github.com/hashicorp/openstack

Install jq

jq is a command line tool for parsing JSON document. It'll be used to automate the configuration file creation.

apt-get install jq

Fetch your openrc.sh configuration

From the OVHcloud Console, fetch your openrc.sh configuration file: in the left-hand menu of your Public Cloud project, click Project Management, then the Users tab, click the ... button on the row of your OpenStack user and select Download the OpenStack RC file. You might need to create an OpenStack user before.

Install openstack command line client

The easier way is to use a Python virtual environment

python3 -m venv venv3 # creates a virtualenv named venv3
. ./venv3/bin/activate # enter the virtualenv
pip install --upgrade pip
pip install python-openstackclient

or install your distribution package apt-get install python-openstackclient

Verification

After sourcing the openrc.sh file, test your local setup with

. ./openrc.sh
openstack token issue

Packer configuration

First, source your openrc.sh file with

. ./openrc.sh

Next, find the required IDs. You'll need the ID of the image, flavor and network. We'll build our image from Ubuntu 24.04 on a b2-7 hardware, with an interface connected on public network Ext-Net.

export SOURCE_ID=`openstack image list -f json | jq -r '.[] | select(.Name == "Ubuntu 24.04") | .ID'`
export FLAVOR_ID=`openstack flavor list -f json | jq -r '.[] | select(.Name == "b2-7") | .ID'`
export NETWORK_ID=`openstack network list -f json | jq -r '.[] | select(.Name == "Ext-Net") | .ID'`

INFO: for FLAVOR_ID, you can directly use the name, i.e., b2-7

Finally, create a packer.json file

cat > packer.json <<EOF
{
    "variables": {
        "os_region_name": "{{env `OS_REGION_NAME`}}",
        "os_tenant_id": "{{env `OS_TENANT_ID`}}",
        "source_id": "{{env `SOURCE_ID`}}",
        "flavor_id": "{{env `FLAVOR_ID`}}",
        "network_id": "{{env `NETWORK_ID`}}"
    },
    "builders": [
        {
            "type": "openstack",
            "region": "{{user `os_region_name`}}",
            "tenant_id": "{{user `os_tenant_id`}}",
            "image_name": "My Custom Image",
            "ssh_username": "ubuntu",
            "source_image": "{{user `source_id`}}",
            "flavor": "{{user `flavor_id`}}",
            "ssh_ip_version": "4",
            "networks": [
                "{{user `network_id`}}"
            ]
        }
    ],
    "provisioners": [
        {
            "script": "setup_vm.sh",
            "type": "shell"
        }
    ]
}
EOF

In the last section of the configuration file, we specify a setup_vm.sh shell script to be run.

#!/bin/sh

set -ex

if [ `id -u` -ne 0 ]; then
     sudo $0
    exit 0
fi

## your custom code below
apt-get install git
git clone ...

Building the image

Using the configuration file above, validate and build the image:

packer validate packer.json
packer build packer.json

If all went OK, you should have a new image available. You can check with

openstack image list | grep 'My Custom Image'

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