Desktop and kiosk sessions

A package can declare a login session beside its application entrypoints. Windowed and login launches use the same installed version, writable state, user profile, and update channel.

Manifest

Declare an exported entrypoint and a separate permission set:

"sessions": [
  {
    "id": "com.example.desktop",
    "name": "Example Desktop",
    "description": "Example desktop session",
    "kind": "desktop",
    "entrypoint": "/usr/bin/example-session",
    "override": {
      "deviceDri": true,
      "deviceInput": true,
      "hostApplications": true,
      "filesystem": [
        { "path": "xdg-documents", "access": "read-write" },
        { "path": "xdg-download", "access": "read-write" }
      ]
    }
  }
]

kind accepts desktop and kiosk. The identifier is global and cannot replace a system session or a session owned by another package. The entrypoint must also appear in binaries.

System authority

Install the system authority once:

cpak system setup
cpak system status

The setup installs a fixed root-owned launcher, D-Bus activation policy, and Polkit actions. Package sessions are registered separately.

Register a session

cpak session list github.com/example/desktop
cpak session enable github.com/example/desktop com.example.desktop

cpak shows the session permissions before registration. Polkit then asks for authorization. The privileged service accepts validated metadata and a package origin. The generated display manager entry calls the fixed cpak launcher with the registered session identifier.

Remove one session with:

cpak session disable com.example.desktop

Removing the last installed package version which provides that identifier also unregisters it. cpak system remove removes registered cpak sessions before deleting the system authority.

Display manager support

cpak stores login entries in /usr/local/share/wayland-sessions, the local system data directory defined by the XDG base directory specification. cpak system setup configures display managers which do not search that directory by default.

For example, tuigreet accepts the cpak directory through its existing session option:

tuigreet --sessions /usr/local/share/wayland-sessions:/usr/share/wayland-sessions

Other display managers can use the generated entries when they scan XDG system data directories or allow /usr/local/share/wayland-sessions to be added to their session path.