How to create images¶

If you want to create and share your own images, you can do this either based on an existing instance or snapshot or by building your own image from scratch.

Publish an image from an instance or snapshot¶

If you want to be able to use an instance or an instance snapshot as the base for new instances, you should create and publish an image from it.

When publishing an image from an instance, make sure that the instance is stopped.

To publish an image from an instance, enter the following command:

lxc publish <instance_name> [<remote>:]

To publish an image from a snapshot, enter the following command:

lxc publish <instance_name>/<snapshot_name> [<remote>:]

In both cases, you can specify an alias for the new image with the --alias flag, set an expiration date with --expire and make the image publicly available with --public. If an image with the same name already exists, add the --reuse flag to overwrite it. See lxc publish --help for a full list of available flags.

To publish an image from an instance or a snapshot, send a POST request with the suitable source type to the /1.0/images endpoint.

To publish an image from an instance:

lxc query --request POST /1.0/images --data '{
  "source": {
    "name": "<instance_name>",
    "type": "instance"
  }
}'

To publish an image from a snapshot:

lxc query --request POST /1.0/images --data '{
  "source": {
    "name": "<instance_name>/<snapshot_name>",
    "type": "snapshot"
  }
}'

In both cases, you can include additional configuration (for example, you can include aliases, set a custom expiration date, or make the image publicly available). For example:

lxc query --request POST /1.0/images --data '{
  "aliases": [ { "name": "<alias>" } ],
  "expires_at": "2025-03-23T20:00:00-04:00",
  "public": true,
  "source": {
    "name": "<instance_name>",
    "type": "instance"
  }
}'

See POST /1.0/images for more information.

The publishing process can take quite a while because it generates a tarball from the instance or snapshot and then compresses it. As this can be particularly I/O and CPU intensive, publish operations are serialized by LXD.

Prepare the instance for publishing¶

Before you publish an image from an instance, clean up all data that should not be included in the image. Usually, this includes the following data:

Instance metadata (use lxc config metadata or PATCH /1.0/instances/{name}/metadata/PUT /1.0/instances/{name}/metadata to edit)
File templates (use lxc config template or POST /1.0/instances/{name}/metadata/templates to edit)
Instance-specific data inside the instance itself (for example, host SSH keys and dbus/systemd machine-id)

Build an image¶

For building your own images, you can use LXD image builder.

See the LXD image builder documentation for instructions for installing and using the tool.

Repack a Windows image¶

You can run Windows VMs in LXD. To do so, you must repack the Windows ISO with LXD image builder.

See the LXD image builder tutorial for instructions, or How to install a Windows 11 VM using LXD for a full walk-through.