Snapcraft app and service metadata

The app keys and values in snapcraft.yaml detail the applications and services that a snap wants to expose, including how they’re executed and which resources they can access.

See Snapcraft top-level metadata and Snapcraft parts metadata for details on how apps and parts are configured within snapcraft.yaml.

apps

Type: dict

A map of app-names representing entry points to run for the snap.

apps.<app-name>

Type: dict

The name exposed to run a program inside the snap.

If <app-name> is the same as name, the program will be invoked as app-name. However, if they differ, the program will be exposed as <snap-name>.<app-name>.

Keys for apps

The following are keys that can be within apps. (for example, apps.<app-name>.daemon):

adapter

Type enum
Can be one of the following:

Snapcraft normally creates a wrapper holding common environment variables. Disabling this could be useful for minimal base snaps without a shell, and for statically linked binaries with no use for an environment.

command

Type: string

The command to run inside the snap when <app-name> is invoked.

The command can be in either a snap runtime’s command path, $SNAP/usr/sbin:$SNAP/usr/bin:$SNAP/sbin:$SNAP/bin, or an executable path relative to $SNAP.

If daemon is set, this will be the command to run the service. Only a snap with classic confinement can use a relative path because PATH isn’t modified by a wrapper in classic confinement. See Classic confinement for more details.

Examples: app-launch for an excecutable placed under $SNAP/bin. With classic confinement, bin/app-launch for an executable placed under $SNAP/bin.

command-chain

Type: Array of string

A list of command to be executed, in order, before the command referenced by apps.<app-name>.command.

See Proposal: support command-chain in apps and hooks for further details.

To ensure that the Snapd distribution user running supports this feature, insert the command-chain value to the assumes property.

common-id

Type: string

An identifier to a desktop-id within an external appstream file.

See Using external metadata for more details.

daemon

Type: enum

Declares that <app-name> is a system daemon.

Can be one of the following:

  • simple: the command is the main process.
  • oneshot: the configured command will exit after completion
  • forking: the configured command calls fork() as part of its start-up. The parent process is then expected to exit when start-up is complete
  • notify: the command configured will send a signal to systemd to indicate that it’s running.

desktop

Type: string

Location of the .desktop file.

A path relative to the prime directory pointing to a desktop file, commonly used to add an application to the launch menu. Snapcraft will take care of the rest.

Examples: usr/share/applications/my-app.desktop and share/applications/my-app.desktop

environment

Type: dict

A set of key-value pairs specifying the contents of environment variables.

Key is the environment variable name; Value is the contents of the environment variable.

Example: LANG: C.UTF-8

extensions

Type: list[string]

Extensions to apply to this application.

Example: [gnome-3-28]

listen-stream

Type: string

The socket abstract name or socket path.

Sockets should go to a map of <socket-name>\ to objects which specify the listen-stream and (optionally) the socket-mode.

TCP socket syntax: <port>, [::]:<port>, [::1]:<port> and 127.0.0.1:<port>
UNIX socket syntax: $SNAP_DATA/<path>, $SNAP_COMMON/<path> and @snap.<snap name>.<suffix>

Example:

      unix:
        listen-stream: $SNAP_COMMON/lxd/unix.socket
        socket-mode: 0660

passthrough

Type: type[object]

<app-name> attributes to pass through to snap.yaml without snapcraft validation.

See Using in-development features for further details.

plugs

Type: list[string]

Plugs for interfaces to connect to.

<app-name> will make these plug connections when running in strict confinement For interfaces that need attributes, see top-level plugs.

Example: [home, removable-media, raw-usb]

post-stop-command

Type: string

Runs a command from inside the snap after a service stops.

Requires daemon to be set as the snap type.

restart-condition

Type: enum

Condition to restart the daemon under.

Defaults to on-failure. Other values are [on-failure|on-success|on-abnormal|on-abort|always|never]. Refer to systemd.service manual for details.

Requires daemon to be set as the snap type.

slots

Type: list[string]

Slots for interfaces to connect to.

<app-name> will make these slot connections when running in strict confinement only. For interfaces that need attributes, see top-level slots.

Example: [home, removable-media, raw-usb]

socket

Type: dict

Maps a daemon’s sockets to services and activates them.

Requires an activated daemon socket.

Requires apps.<app-name>.plugs to declare the network-bind plug.

socket-mode

Type: integer

The mode of a socket in octal.

stop-command

Type: string

The path to a command inside the snap to run to stop the service.

Requires daemon to be set as the snap type.

stop-timeout

Type: string

The length of time to wait before terminating a service.

Time duration units can be 10ns, 10us, 10ms, 10s, 10m. Termination is via SIGTERM (and SIGKILL if that doesn’t work).

Requires daemon to be set as the snap type.

Last updated 17 days ago. Help improve this document in the forum.