charmlibs-snap

snap manages snaps on the machine a charm runs on, by talking to snapd over its REST API. Function names, arguments, and error behaviour follow the snap command line, so what you know from the CLI carries over.

To install, add charmlibs-snap to your Python dependencies. Then in your Python code, import as:

from charmlibs import snap

See the reference documentation for more.

Upgrading from 1.x? Version 2.0 is a rewrite with a new API -- see how to migrate from 1.x to 2.0. This README and the library docs cover the 2.x series; for 1.x, see the snap-v1.0.1.post0 tag.

Getting started

Every operation is a module-level function that takes the snap's name. To make sure a snap is installed on a particular channel, and refresh it if an update is available:

from charmlibs import snap

snap.ensure_installed('lxd', '5.21/stable')

ensure_installed installs the snap if it's absent, refreshes it if it's on the wrong channel or revision, and otherwise refreshes it if an update is available. It returns a truthy value if anything changed.

Configure the snap and manage its services:

snap.set('lxd', {'core.https_address': ':8443'})
snap.get_one('lxd', 'core.https_address')  # ':8443'
snap.start('lxd', 'daemon', enable=True)

Query the installed snap's state with list_one, which returns an InstalledInfo:

info = snap.list_one('lxd')
info.tracking  # '5.21/stable'
info.revision  # '33110'
info.version  # '5.21.3'

Install or refresh to a specific revision, and hold the snap so that automatic refreshes don't move it:

snap.refresh('lxd', '5.21/stable', revision=33110)
snap.hold('lxd')