added image creation from public lxd server

doc/source/images.rst

@@ -24,6 +24,10 @@ image:
     set `public` to `True`.
   - `create_from_simplestreams(server, alias, public=False, auto_update=False, wait=False)` -
     Create an image from simplestreams.
+  - `create_from_imagecreate_from_image(cls, client, server, fingerprint=None, alias=None,
+                                        public=False, auto_update=False, secret=None,
+                                        certificate=None):` -
+    Create an image from a public lxd instance.
   - `create_from_url(url, public=False, auto_update=False, wait=False)` -
     Create an image from a url.
 
@@ -99,6 +103,23 @@ you may also want to `wait=True`.
     >>> image.fingerprint
     'e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855'
 
+You can also download existing images from a remote lxd instance by either their alias or fingerprint.
+
+.. code-block:: python
+
+    >>> image = client.images.create_from_image("https://images.nlogn.org:8443",
+                                                alias='fedora/30', public=False, auto_update=True)
+    >>> image.fingerprint
+    'e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855'
+
+Or fetch an image from a simplestream server with:
+
+.. code-block:: python
+
+    >>> image = client.images.create_from_simplestreams('https://cloud-images.ubuntu.com/releases',
+                                                        'trusty/amd64', public=False, auto_update=True)
+    >>> image.fingerprint
+    'e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855'
 
 Finally, delete an image. As this is an asynchonous operation,
 you may also want to `wait=True`.

pylxd/models/image.py

@@ -157,6 +157,62 @@ def create_from_simplestreams(
 
         return client.images.get(op.metadata["fingerprint"])
 
+    @classmethod
+    def create_from_image(
+        cls,
+        client,
+        server,
+        fingerprint=None,
+        alias=None,
+        public=False,
+        auto_update=False,
+        secret=None,
+        certificate=None,
+    ):
+        """Copy an image from remote lxd.
+        :param client:  the pylxd client
+        :type client: pylxd.Client
+        :param server: URL of the remote LXD-API
+        :type server: str
+        :param fingerprint: The fingerprint of the image to fetch
+            (mandatory if no alias is provided)
+        :type fingerprint: str
+        :param alias: The alias of the image to fetch
+            (mandatory if no fingerprint is provided)
+        :type alias: str
+        :param public: Make the new image public
+        :type public: bool
+        :param auto_update: Set the image to auto-update
+        :type auto_update: bool
+        :param secret: Secret to authenticate to remote lxd instance
+        :type secret: str
+        :param certificate: Optional PEM certificate.
+            If not mentioned, system CA is used.
+        :type certificate: str
+        :returns: newly created image
+        :rtype: pylxd.Image
+        """
+        config = {
+            "public": public,
+            "auto_update": auto_update,
+            "source": {
+                "type": "image",
+                "mode": "pull",
+                "server": server,
+                "protocol": "lxd",
+                "fingerprint": fingerprint,
+                "alias": alias,
+                "secret": secret,
+                "certificate": certificate,
+            },
+        }
+        if alias is not None:
+            config["aliases"] = [{"name": alias}]
+
+        op = _image_create_from_config(client, config, wait=True)
+
+        return client.images.get(op.metadata["fingerprint"])
+
     @classmethod
     def create_from_url(cls, client, url, public=False, auto_update=False):
         """Copy an image from an url."""

pylxd/tests/models/test_image.py

@@ -391,6 +391,16 @@ def test_create_from_simplestreams(self):
             image.fingerprint,
         )
 
+    def test_create_from_image(self):
+        """Try to create an image from image at public lxd."""
+        image = self.client.images.create_from_image(
+            "https://images.nlogn.org:8443", alias="debian/8"
+        )
+        self.assertEqual(
+            "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855",
+            image.fingerprint,
+        )
+
     def test_create_from_url(self):
         """Try to create an image from an URL."""
         image = self.client.images.create_from_url("https://dl.stgraber.org/lxd")