Snapd

Snapd is a background service and set of tools that manage snaps, a packaging format developed by Canonical for Linux distributions. It provides the runtime, tooling, and governance needed to install, refresh, and remove snap packages and to manage their confinement and interfaces. Snapd is designed to work across multiple distributions, with Ubuntu being its primary platform.

The snap ecosystem centers on the snapd daemon, which runs with root privileges and coordinates interactions with the Snap Store or other repositories. Snap commands are issued via the snap CLI, which communicates with snapd over D-Bus to perform operations such as install, update, revert, or refresh. Snaps are delivered as read-only images that include all dependencies, enabling consistent application behavior across different systems.

Key features of snapd include transactional updates with rollback, automatic and scheduled updates, and system-wide confinement. Confinement restricts what a snap can access through AppArmor or SELinux profiles and a defined set of interfaces, which can be connected or disconnected to grant necessary permissions. There is also an optional classic confinement mode for certain applications that require broader access.

Snaps can be updated automatically, with mechanisms to defer updates and to revert if problems arise. Snapd maintains the state of installed snaps, their content, and their interfaces in its data stores, typically under /var/lib/snapd. Although closely associated with Ubuntu, snapd is available on many Linux distributions and competes with other packaging systems such as Flatpak and AppImage in the broader software deployment landscape.