Containers

Container objects are the core of LXD. Containers can be created, updated, and deleted. Most of the methods for operating on the container itself are asynchronous, but many of the methods for getting information about the container are synchronous.

Manager methods

Containers can be queried through the following client manager methods:

  • exists(name) - Returns boolean indicating if the container exists.
  • all() - Retrieve all containers.
  • get() - Get a specific container, by its name.
  • create(config, wait=False) - Create a new container. This method requires the container config as the first parameter. The config itself is beyond the scope of this documentation. Please refer to the LXD documentation for more information. This method will also return immediately, unless wait is True.

Container attributes

For more information about the specifics of these attributes, please see the LXD documentation.

  • architecture - The container architecture.
  • config - The container config
  • created_at - The time the container was created
  • devices - The devices for the container
  • ephemeral - Whether the container is ephemeral
  • expanded_config - An expanded version of the config
  • expanded_devices - An expanded version of devices
  • name - (Read only) The name of the container. This attribute serves as the primary identifier of a container
  • description - A description given to the container
  • profiles - A list of profiles applied to the container
  • status - (Read only) A string representing the status of the container
  • last_used_at - (Read only) when the container was last used
  • status_code - (Read only) A LXD status code of the container
  • stateful - (Read only) Whether the container is stateful

Container methods

  • rename - Rename a container. Because name is the key, it cannot be renamed by simply changing the name of the container as an attribute and calling save. The new name is the first argument and, as the method is asynchronous, you may pass wait=True as well.
  • save - Update container’s configuration
  • state - Get the expanded state of the container.
  • start - Start the container
  • stop - Stop the container
  • restart - Restart the container
  • freeze - Suspend the container
  • unfreeze - Resume the container
  • execute - Execute a command on the container. The first argument is a list, in the form of subprocess.Popen with each item of the command as a separate item in the list. Returns a tuple of (exit_code, stdout, stderr). This method will block while the command is executed.
  • migrate - Migrate the container. The first argument is a client connection to the destination server. This call is asynchronous, so wait=True is optional. The container on the new client is returned.
  • publish - Publish the container as an image. Note the container must be stopped in order to use this method. If wait=True is passed, then the image is returned.

Examples

If you’d only like to fetch a single container by its name…

>>> client.containers.get('my-container')
<container.Container at 0x7f95d8af72b0>

If you’re looking to operate on all containers of a LXD instance, you can get a list of all LXD containers with all.

>>> client.containers.all()
[<container.Container at 0x7f95d8af72b0>,]

In order to create a new Container, a container config dictionary is needed, containing a name and the source. A create operation is asynchronous, so the operation will take some time. If you’d like to wait for the container to be created before the command returns, you’ll pass wait=True as well.

>>> config = {'name': 'my-container', 'source': {'type': 'none'}}
>>> container = client.containers.create(config, wait=False)
>>> container
<container.Container at 0x7f95d8af72b0>

If you were to use an actual image source, you would be able to operate on the container, starting, stopping, snapshotting, and deleting the container.

>>> config = {'name': 'my-container', 'source': {'type': 'image', 'alias': 'ubuntu/trusty'}}
>>> container = client.containers.create(config, wait=True)
>>> container.start()
>>> container.freeze()
>>> container.delete()

Config line with a specific image source and a profile.

>>> config = {'name': 'my-container', 'source': {'type': 'image', "mode": "pull", "server":
    "https://cloud-images.ubuntu.com/daily", "protocol": "simplestreams", 'alias': 'bionic/amd64'},
    'profiles': ['profilename'] }

To modify container’s configuration method save should be called after Container attributes changes.

>>> container = client.containers.get('my-container')
>>> container.ephemeral = False
>>> container.devices = { 'root': { 'path': '/', 'type': 'disk', 'size': '7GB'} }
>>> container.save

To get state information such as a network address.

>>> addresses = container.state().network['eth0']['addresses']
>>> addresses[0]
{'family': 'inet', 'address': '10.251.77.182', 'netmask': '24', 'scope': 'global'}

Container Snapshots

Each container carries its own manager for managing Snapshot functionality. It has get, all, and create functionality.

Snapshots are keyed by their name (and only their name, in pylxd; LXD keys them by <container-name>/<snapshot-name>, but the manager allows us to use our own namespacing).

A container object (returned by get or all) has the following methods:

  • rename - rename a snapshot
  • publish - create an image from a snapshot. However, this may fail if the image from the snapshot is bigger than the logical volume that is allocated by lxc. See https://github.com/lxc/lxd/issues/2201 for more details. The solution is to increase the storage.lvm_volume_size parameter in lxc.
>>> snapshot = container.snapshots.get('an-snapshot')
>>> snapshot.created_at
'1983-06-16T2:38:00'
>>> snapshot.rename('backup-snapshot', wait=True)
>>> snapshot.delete(wait=True)

To create a new snapshot, use create with a name argument. If you want to capture the contents of RAM in the snapshot, you can use stateful=True. .. note:: Your LXD requires a relatively recent version of CRIU for this.

>>> snapshot = container.snapshots.create(
...     'my-backup', stateful=True, wait=True)
>>> snapshot.name
'my-backup'

Container files

Containers also have a files manager for getting and putting files on the container. The following methods are available on the files manager:

  • put - push a file into the container.
  • get - get a file from the container.
  • delete_available - If the file_delete extension is available on the lxc host, then this method returns True and the delete method is available.
  • delete - delete a file on the container.

Note

All file operations use uid and gid of 0 in the container. i.e. root.

>>> filedata = open('my-script').read()
>>> container.files.put('/tmp/my-script', filedata)
>>> newfiledata = container.files.get('/tmp/my-script2')
>>> open('my-script2', 'wb').write(newfiledata)