How to Prepare Your Own OS Image & Deploy it on Cloud Server

You can deploy a cloud server from your own custom image. This is useful when you need:

• An operating system that is not yet available among our ready-to-use images in the customer portal
• A preconfigured image with your own software and settings

For the purpose of this article, images are grouped into two categories:

• Cloud-compatible images – provided by the OS vendor for cloud environments. They typically include the required drivers, cloud-init support, and OpenStack compatibility
• Non-cloud images – generic images, such as ISO-based installers, that require additional configuration before they can run properly in an OpenStack-based cloud

This guide covers how to create, customize, and prepare a virtual machine (VM) image and then upload it to the customer portal to deploy a cloud server. It walks through three scenarios:

1. Deploying a cloud server using a cloud-compatible image without modifications (as-is)
2. Preparing and customizing a cloud-compatible image before uploading
3. Preparing a non-cloud image (for example, from an ISO file) to make it OpenStack-compatible
   
   

This article does not cover the operating system installation process.

Prerequisites

• Customer portal account
• Added SSH key to the customer portal (required only if you plan to use key-based authentication)
• Local machine (Windows, Linux, or macOS)
• Installed virtualization software (we use QEMU in examples)
• Source OS image

Image requirements

Our cloud services are built on OpenStack. You can configure all parameters and applications as needed, and ensure your VM meets the following core OpenStack image requirements:

For the complete list of requirements, see the OpenStack Image Guide.

Cloud-init compatibility

Cloud-init supports a wide range of Linux and BSD distributions. For the list of supported platforms, see: https://docs.cloud-init.io/en/latest/reference/availability.html.

You can find unofficial BSD images that include cloud-init and have been tested on OpenStack at: https://bsd-cloud-image.org/.

Installing QEMU

In this guide we use QEMU, a free and open-source cross-platform virtualization environment. After installing QEMU, you can start a VM with your OS image.

Ubuntu/Linux

sudo apt-get install qemu-system

Fedora

sudo dnf install qemu qemu-kvm
#or
dnf install @virtualization

Red Hat/CentOS

sudo yum install qemu qemu-kvm

SUSE

zypper install qemu

Arch Linux

sudo pacman -S qemu

macOS

From Homebrew:

brew install qemu

From MacPorts:

sudo port install qemu

Windows

Open PowerShell and run the following command with administrator rights:

winget install SoftwareFreedomConservancy.QEMU

Or use a ready-made installer for Windows.

Cloud-init setup

Cloud-init is a cross-platform tool used to initialize a virtual machine during its first boot and apply configuration through metadata. Typical tasks include setting the hostname, configuring networking, adding SSH keys, creating users, and running initialization commands or scripts.

Cloud-init configuration files

To provide initialization data when preparing an image locally, this guide uses a small ISO file called seed.iso. During the first boot, cloud-init reads the contents of this ISO and applies the defined settings.

The ISO contains two files:

• user-data – defines users, SSH keys, and other initialization settings

• meta-data – specifies basic instance parameters, such as hostname

Create two plain text files named user-data and meta-data (without file extensions) and place them in the same directory before building the ISO.

Example user-data:

#cloud-config
users:
  - name: cloud-user
    shell: /bin/bash
    groups: sudo
    sudo: ALL=(ALL) NOPASSWD:ALL
    ssh_authorized_keys:
      - INSERT_YOUR_SSH_KEY_HERE

  - name: admin
    shell: /bin/bash
    groups: sudo
    sudo: ALL=(ALL) NOPASSWD:ALL
    ssh_authorized_keys:
      - INSERT_YOUR_SSH_KEY_HERE

ssh_pwauth: false
hostname: fedora-vm

Example meta-data:

local-hostname: fedora-vm

Specifying local-hostname in meta-data is sufficient; instance-id is generated automatically by cloud-init.

Then pack these files into an ISO image that will later be attached to the virtual machine.

Build the seed.iso

Use one of the supported tools to generate a compatible ISO. The recommended method is cloud-localds. If not available, use mkisofs or genisoimage.

Linux / macOS

Run the command directly in the directory that contains these files.

cloud-localds seed.iso user-data meta-data

Alternatives:

mkisofs -output seed.iso -volid cidata -joliet -rock user-data meta-data
or
genisoimage -output cidata.iso -volid cidata -joliet -rock -graft-points user-data=./user-data meta-data=./meta-data 

Windows

1. Install the Windows Assessment and Deployment Kit (Windows ADK), selecting only the Deployment Tools component
2. Execute the following command:
   

   C:\path-to-oscdimg-exe-file -j1 -lcidata C:\path-to-cloud-init-config-files .\seed.iso

   The oscdimg.exe utility is typically located at:

   %ProgramFiles(x86)%\Windows Kits\<Windows version>\Assessment and Deployment Kit\Deployment Tools\<architecture>\Oscdimg\oscdimg.exe

   Where:

   • <Windows version> is your installed Windows Kits version
   • <architecture> is amd64 or arm64, depending on your system

A seed.iso file will be created in the same directory.

Launching a VM with QEMU

Start the virtual machine with your OS image and the seed.iso attached.

Linux

qemu-system-x86_64 \
  -m 2048 -smp 2 \
  -drive file=cloud-image.qcow2,format=qcow2,if=virtio \
  -drive file=seed.iso,format=raw,if=virtio \
  -netdev user,id=net0,hostfwd=tcp::2222-:22 \
  -device virtio-net,netdev=net0 \
  -nographic

For subsequent boots, remove the line -drive file=seed.iso,format=raw,if=virtio

macOS

qemu-system-x86_64 \
  -accel tcg,thread=multi \
  -m 2048 -smp 2 \
  -drive file=generic_alpine.qcow2,format=qcow2,if=virtio \
  -cdrom seed.iso \
  -device virtio-net-pci,netdev=n1 \
  -netdev user,id=n1,hostfwd=tcp::2222-:22 \
  -nographic

For subsequent boots, remove the line -cdrom seed.iso

Windows

Navigate into the QEMU installation directory (%ProgramFiles%\qemu, by default) and run the VM with the following command:

.\qemu-system-x86_64.exe ^
  -m 2048 -smp 2 ^
  -drive file=,format=qcow2,if=virtio ^ 
  -cdrom  ^ 
  -device virtio-net-pci,netdev=n1 ^ 
  -netdev user,id=n1,hostfwd=tcp::2222-:22

For subsequent boots, remove the line -cdrom <C:\path-to-seed.iso>.

Check applied configuration

After the VM starts, connect to it via SSH using the command:

ssh -p 2222 <user>@localhost

To verify cloud-init behavior, run:

cloud-init status --long

Case 1: Deploying from a cloud-compatible image without customization (as is)

You can deploy a cloud server directly from a vendor-provided cloud-compatible image without creating a local virtual machine first. This method is useful if you need to deploy a cloud server from a vendor-provided image that is not available in our catalog and you do not require any customization. To do this:

1. Download the vendor cloud image
2. Upload the image to the customer portal and create a cloud server (see Uploading image to the customer portal)
3. Connect via SSH as the default user preinstalled in the image (see Default users in vendor-provided cloud images)
   For Alpine, this is alpine:
   

   ssh alpine@<cloud_server_public_ip>

Example: Creating a privileged user after creating a cloud server

1. Switch to the root user
   

   doas -s

2. Install and configure sudo
   

   apk update
   apk add sudo
   adduser alpine wheel

3. Create a new administrative user
   

   adduser cloud-user
   adduser cloud-user wheel

4. Configure SSH access for the new user
   

   mkdir -p /home/cloud-user/.ssh
   echo 'ssh-rsa your_public_SSH_key' > /home/cloud-user/.ssh/authorized_keys
   chmod 700 /home/cloud-user/.ssh
   chmod 600 /home/cloud-user/.ssh/authorized_keys
   chown -R cloud-user:cloud-user /home/cloud-user/.ssh

5. Edit SSH configuration
   • Open /etc/ssh/sshd_config with vi or install nano (recommended):
     

     apk add nano
     nano /etc/ssh/sshd_config

   • Make sure these lines are present and uncommented:
     

     PubkeyAuthentication yes
     PasswordAuthentication no

   • Check if the user is unlocked

     Open /etc/shadow and ensure the line for cloud-user does not contain "!"

     If it does, replace it with:

     cloud-user:*:::::::

     This allows SSH login while keeping password authentication disabled.

6. Restart the SSH service
   

   rc-service sshd restart

7. From your local machine, connect to the server as the new user:
   

   ssh admin@<server_ip>

The server now supports login using the admin account with key-based SSH authentication and administrative privileges via sudo.

Case 2: Deploying from a cloud-compatible image with customization

This section explains how to customize a vendor-provided cloud-compatible image before uploading it to the customer portal.

Since these images already include cloud-init, you only apply your changes and save the updated image. These images already include cloud-init, so you can configure the VM, install software, adjust system settings, create users, and then save the updated image for deployment.

1. Download the vendor's cloud image
2. Create cloud-init configuration (user-data and meta-data) and generate the seed.iso
   • See Cloud-init setup
3. Start the VM with QEMU
   • Launch the VM using the cloud image and attach the seed.iso so cloud-init applies your configuration on the first boot
   • See Launching a VM with QEMU
4. Inside the VM, install and configure the guest OS as you need
5. Verify the VM meets the OpenStack Image requirements
6. Shut down the VM and optimize the image
   • See Preparing the image for upload
7. Upload the image to the customer portal and deploy a cloud server
   • See Uploading the image to the customer portal

Case 3: Deploying from a non-cloud-compatible ISO image

This section covers preparing a VM created from an ISO image, that does not include cloud-init or any cloud-specific configuration. The goal is simply to make the image boot correctly in OpenStack and accept initialization meta-data during the first launch.

Create a local virtual disk

When installing an OS from an ISO, you must first create a virtual disk, because the ISO is not a disk image. This creates the disk file.

Note: it does not mount it anywhere (QEMU will mount it when you run -drive file=…). You can choose any <disk-size> that fits your OS installation requirements (for example, 4G).

Linux, macOS etc

qemu-img create -f qcow2 path-to-cloud-image.qcow2 <disk-size>

Windows

Navigate into the QEMU installation directory (%ProgramFiles%\qemu, by default), and run the following command:

.\qemu-img.exe create -f qcow2 C:\path-to-cloud-image.qcow2 <disk-size>

Start QEMU with the OS installation ISO

The first boot must use the installation ISO (for example, ubuntu-25.10-live-server-amd64.iso). The seed.iso is not used at this stage, because cloud-init is not yet installed.

Attach the ISO as a virtual CD-ROM device. See Launching a VM with QEMU.

...
-cdrom ubuntu-25.10-live-server-amd64.iso \
-boot order=d \
...

This lets the VM boot from the OS installer instead of booting from the empty virtual disk.

Install and configure the guest OS as you need

Cloud-init does not require a "clean" system. Your ISO-based image may already contain:

• Installed packages (for example, MySQL, nginx)
• System users created by those packages
• Pre-configured settings and services that start on boot

Restart the VM without the installation ISO and the boot order=d parameter

boot order=d tells QEMU to boot from the CD-ROM. After the OS is installed, the VM must boot from its virtual disk instead.

Make sure the SSH server is installed and running

sudo apt install openssh-server
sudo systemctl enable ssh
sudo systemctl start ssh

Install cloud-init and disk auto-expansion utilities

cloud-init is a common init that will:

• Fetch metadata and user data (SSH keys, hostname, and so on)
• Create the desired user (for example, cloud-user or any user you use as the default)
• Run the growpart and resizefs modules to expand the disk

Utilities such as cloud-utils or cloud-utils-growpart provide growpart for automatically expanding the root partition when the flavor disk is larger than the original image.

RPM-based

sudo dnf install -y cloud-init
sudo systemctl enable cloud-init

Debian-based

sudo apt update
sudo apt install -y cloud-init
sudo systemctl enable cloud-init

Configure cloud-init datasources

1. Create a configuration file in the VM:
   

   /etc/cloud/cloud.cfg.d/99-openstack-datasource.cfg

   /etc/cloud/cloud.cfg.d/ directory is the standard place for user overrides. The 99- prefix in the file name makes sure this configuration is loaded last. Files are processed in alphabetical order, so 99-openstack-datasource.cfg overrides earlier datasource_list settings.
2. Add, for example:
   

   datasource_list: [NoCloud, Ec2, ConfigDrive]

   This tells cloud-init to look for instance metadata and user data using standard OpenStack-compatible datasources, including NoCloud, which you will emulate via iso.

Apply cloud-init metadata and Start QEMU

To provide initialization data for your image, attach the previously created seed.iso (see Cloud-init setup). When the ISO is attached to the VM, cloud-init reads it as a NoCloud datasource and applies the configuration from user-data and meta-data during the first boot. After initialization completes, seed.iso is no longer required and can be removed for all subsequent VM launches.

Verify the disk layout and auto-expansion

OpenStack expects the image to expand the root partition and filesystem on first boot if the flavor disk size is larger than the original image.

Do the following:

• Make sure the disk layout is simple (a single root partition, as created by the default Ubuntu installer)
• Check that growpart and resizefs are present in the module lists in /etc/cloud/cloud.cfg

grep -A3 -i growpart /etc/cloud/cloud.cfg
grep -A3 -i resizefs /etc/cloud/cloud.cfg

Remove hard-coded network settings

For modern Ubuntu (netplan):

• Check /etc/netplan/*.yaml and make sure dhcp4: true is used,
• There must be no static IP, MAC address, or interface names tied to a specific MAC

If the system is configured for DHCP by default, you usually do not need to change anything.

If the file 70-persistent-net.rules exists, it is recommended to remove it to avoid persisting old MAC addresses:

cat /etc/udev/rules.d/70-persistent-net.rules
rm /etc/udev/rules.d/70-persistent-net.rules

Do a final cleanup

Remove VM-specific state and temporary data so that each new instance starts "clean":

• Clear cloud-init state (/var/lib/cloud)
• Optionally clear cloud-init logs and systemd journals
• Make sure that:
  • There are no permanently baked-in SSH host keys, if you want them to be generated on first boot
  • There are no user ~/.ssh/authorized_keys files (keys will be injected through cloud-init)
  • The firewall is disabled

Preparing the image for upload

After you verify that the virtual machine (VM) meets the image requirements, finalize the disk so it is ready for upload to the customer portal. Some preparation steps differ depending on the operating system.

Remove cloud-init state so that the new cloud server boots as a fresh instance:

Linux and FreeBSD/BSD

sudo cloud-init clean --logs
sudo rm -rf /var/lib/cloud/*

For Ubuntu/Debian, also confirm that /etc/cloud/cloud.cfg.d/*.cfg does not contain test-specific datasource overrides.

Delete VM-specific artifacts

Linux

• Delete SSH host keys:
  

  sudo rm -f /etc/ssh/ssh_host_*

• Remove temporary authorized_keys added during local testing:
  

  sudo rm -f /home/*/.ssh/authorized_keys
  sudo rm -f /root/.ssh/authorized_keys

• Remove persistent network rules, if present:
  

  sudo rm -f /etc/udev/rules.d/70-persistent-net.rules

FreeBSD / BSD

Remove host keys and cloud-init or bsd-cloudinit state:

sudo rm /etc/ssh/ssh_host_*
sudo rm -rf /var/db/cloud/*

Shut down the VM cleanly, to ensure that file system and all services write their final state

Linux

sudo shutdown -h now

FreeBSD / BSD

sudo shutdown -p now

The resulting QCOW2 disk is your OpenStack-compatible image.

(Optional) Optimize and compress the image

Use this command to optimize the image:

qemu-img convert -O qcow2 -c original.qcow2 optimized.qcow2

Check the resulting size:

qemu-img info optimized.qcow2

Now the image file is ready for upload to the customer portal.

Uploading the image to the customer portal

1. Upload your image to the customer portal (see How to upload your own image), selecting the the same location where you plan to deploy the cloud server
2. Create a cloud server (see the Create a Cloud Server)
   • In the Image section, select Other and choose your uploaded custom image. Use SSH authentication with the key that matches the public key in your user-data.

Wait for cloud server deployment and get a public IP address to connect to the server in the server's details page.

Default users and access

Access to the deployed server depends on the operating system in the image. See the How to access the cloud server.

Default users in vendor-provided cloud images

Usernames can vary slightly between distributions or custom vendor builds – check the image description page for confirmation.

Use this table to find the default login user for common vendor cloud images.

Useful articles

• How to add new SSH key to a cloud server
• How to create a new SSH key pair
• Connecting to a remote server via SSH