Man page - uwsm(1)

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uwsm

Manual

UWSM

NAME
SYNOPSIS
DESCRIPTION
SUBCOMMANDS
CONFIGURATION
Files
Environment vars
OPERATION OVERVIEW
Login Sequence Integration
Compositor Selection
Startup
Inside session
Shutdown
SUBCOMMANDS
select
check
start
finalize
stop
app
aux
APP DAEMON
SHELL PROFILE INTEGRATION
USE INSIDE DESKTOP ENTRY
SEE ALSO

NAME

UWSM - Universal Wayland Session Manager.

SYNOPSIS

uwsm [-h|-v] { subcommand } [ options ...]

DESCRIPTION

Launches arbitrary wayland compositor via a set of systemd user units to provide graphical user session with environment management, XDG autostart support, clean shutdown. Provides helpers for launching applications as scopes or services.

SUBCOMMANDS

Image grohtml-817703-1.png

See corresponding SUBCOMMANDS subsections below for further info.

Help for each subcommand is accessible by running " uwsm { subcommand } -h ".

CONFIGURATION

Files

In XDG config hierarchy:

Image grohtml-817703-2.png

Fallback is also extended into the system part of XDG data hierarchy, this can be used for distro level defaults.

Environment vars

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OPERATION OVERVIEW

Login Sequence Integration

uwsm can be launched by using conditional exec in shell profile to replace login shell (see Shell Profile Integration section).

Alternatively " uwsm start ..." command can be put into wayland session’s Desktop Entry to be launched by a display manager (see Use Inside Desktop Entry section).

Compositor Selection

uwsm can run arbitrary compositor command line or a Desktop Entry by ID (specifying Action ID is also supported).

Desktop Entry can also be selected via a whiptail menu (see select subcommand section).

Startup

See start subcommand section for command syntax.

UWSM uses a set of units bound to standard user session targets:

•

wayland-session-pre@.target (bound to graphical-session-pre.target )

•

			wayland-wm-env@.service (environment preloader service)
	•		wayland-session@.target (bound to graphical-session.target )

•

			wayland-wm@.service (service for the selected compositor)
	•		wayland-session-xdg-autostart@.target (bound to xdg-desktop-autostart.target )
	•		wayland-session-envelope@.target (lives through entire lifecycle)
	•		wayland-session-shutdown.target (conflicts with targets above for shutdown)
	•		wayland-session-bindpid@.service (PID-tracking session killswitch)
	•		wayland-session-waitenv.service (delays graphical session until vars appear)

Compositor ID (Desktop Entry ID or executable name) becomes the specifier for all templated units.

At the stage of graphical-session-pre.target , the environment saved from " uwsm start " context is loaded (or POSIX shell profile is sourced), uwsm environment files are sourced. The delta is exported to the systemd and D-Bus activation environments by the environment preloader service and is marked for cleanup at shutdown stage. Preloader shell context for convenience has IN_UWSM_ENV_PRELOADER var set to true .

At the stage of graphical-session.target (before it) the main compositor unit wayland-wm@ ${ID} .service and wayland-session-waitenv.service are started.

Compositor should at least put WAYLAND_DISPLAY variable to systemd activation environment. This will trigger uwsm’s automatic finalization logic. Without WAYLAND_DISPLAY in activation environment startup will timeout in 10 seconds.

Manual finalization is possible by running " uwsm finalize " (see finalize subcommand section), also in combination with tweaking UWSM_WAIT_VARNAMES and UWSM_WAIT_VARNAMES_SETTLETIME vars (see Environment vars section).

Successful activation of compositor unit and existence of WAYLAND_DISPLAY in activation environment will allow graphical-session.target to be declared reached.

Finally, xdg-desktop-autostart.target is activated.

Inside session

It is highly recommended to configure the compositor or app launcher to launch apps as scopes or services in special user session slices ( app.slice , background.slice , session.slice ). uwsm provides custom nested slices for apps to live in and be terminated on session end:

	•		app-graphical.slice
	•		background-graphical.slice
	•		session-graphical.slice

A helper app subcommand is provided to handle all the systemd-run invocations for you (see app subcommand section).

The compositor is launched in session.slice by default (as recommended by systemd.special (7)).

Shutdown

Can be initiated by either:

	•		running uwsm stop
	•		stopping *wayland-wm@.service or wayland-session-envelope@.target*
	•		starting wayland-session-shutdown.target

Systemd stops all user units in reverse, as it usually does. During deactivation of graphical-session-pre.target , the environment preloader service cleans activation environments by unsetting all variables that were marked for removal during startup and finalization stages.

Do not use compositor’s native exit mechanism or kill its process directly.

SUBCOMMANDS

select

Selects default wayland session compositor Desktop Entry.

uwsm select

Invokes a whiptail menu to select default session among Desktop Entries in wayland-sessions XDG data hierarchy. Writes to ${XDG_CONFIG_HOME}/uwsm/default-id . Nothing else is done. Returns 1 if selection is cancelled. Can be used for scripting launch condition in shell profile.

check

Performs tests, returns 0 on success, 1 on failure.

is-active :

uwsm check is-active [-h] [-v] [ compositor ]

Image grohtml-817703-4.png

Checks if unit of specific compositor or graphical-session*.target in general is in active or activating state.

may-start :

uwsm check may-start [-h] [-g [ S ]] [-v|-q] [ N ...]

Image grohtml-817703-5.png

Checks whether it is OK to launch a wayland session via the following conditions:

	•		DBUS_SESSION_BUS_ADDRESS is set
	•		Running from login shell
	•		System is at graphical.target
	•		User *graphical-session.target** units are not yet active
	•		Foreground VT is among allowed (default: 1)
	•		Login session’s VT is matching

start

Generates units for given compositor command line or Desktop Entry and starts them.

uwsm start [-h] [-D name [: name ...]] [-a|-e] [-N Name ] [-C Comment ] [-U {run|home}] [-t] [-o] [-n] -- compositor [ args ...]

Image grohtml-817703-6.png

The first argument of the compositor command line acts as an ID and should be either one of:

	•		Executable name
	•		Desktop Entry ID (optionally with " : "-delimited action ID)
	•		Special value:

•

			select - invoke menu to select compositor.
	•		default - run previously selected compositor (or select if no selection was saved).

If given as path, hardcode mode will be used implicitly.

Always use " -- " to disambiguate dashed arguments intended for compositor itself.

After units are (re)generated, wayland-session-bindpid@ ${PID} .service is started, to track the PID of invoking uwsm , then uwsm process replaces itself with systemctl execution that starts wayland-wm@ ${ID} .service and waits for it to finish.

In order to complete the startup sequence, the compositor has to put WAYLAND_DISPLAY into the systemd activation environment. This can be done explicitly by making compositor run " uwsm finalize " command (see the next subsection).

finalize

For running by a compositor on startup.

uwsm finalize [-h] [ VAR_NAME ...]

Exports WAYLAND_DISPLAY , DISPLAY and any defined vars mentioned by names in arguments or in UWSM_FINALIZE_VARNAMES variable (whitespace-separated). Then sends startup notification for the unit to systemd user manager.

This is required if compositor itself does not put WAYLAND_DISPLAY to systemd activation environment, otherwise wayland-session@.service unit or a dedicated wayland-session-waitenv.service unit will terminate due to startup timeout.

UWSM_FINALIZE_VARNAMES variable can be prefilled by plugins.

Direct assignment as VAR_NAME = value is also possible, but recommended only for creating flags for UWSM_WAIT_VARNAMES mechanism.

stop

Stops compositor and optionally removes generated units.

uwsm stop [-h] [-r [ compositor ] [-U {run|home}] [-n]

Image grohtml-817703-7.png

app

Application-to-unit launcher with Desktop Entry support.

uwsm app [-h] [-s { a , b , s , custom .slice}] [-t {scope,service}] [-a app_name ] [-u unit_name ] [-d unit_description ] [-S ] [-T] -- application [ args ...]

Image grohtml-817703-8.png

Application can be provided as a command with optional arguments, or a Desktop Entry ID, optionally suffixed with " : "-delimited Action ID. If Desktop Entry is being launched, arguments should be compatible with it.

Always use " -- " to disambiguate dashed arguments intended for application itself.

aux

For use in systemd user services. Can only be called by systemd user manager.

Image grohtml-817703-9.png

APP DAEMON

Provided as wayland-wm-app-daemon.service to be started on-demand.

Daemon receives app arguments from ${XDG_RUNTIME_DIR}/uwsm-app-daemon-in pipe. Resulting arguments are formatted as shell code and written to ${XDG_RUNTIME_DIR}/uwsm-app-daemon-out pipe.

Arguments are expected to be \0 -delimited, leading \0 are stripped. One command is received per write+close.

The first argument determines the behavior:

	•		app the rest is processed the same as in "uwsm app"
	•		ping just "pong" is returnedn
	•		stop daemon is stoppedn

Single commands are prepended with exec , iterated commands are assembled with trailing & each, followed by wait .

The purpose of all this is to skip all the expensive Python startup and import routines that slow things down every time " uwsm app " is called. Instead the daemon does it once and then listens for requests, while a simple shell script may dump arguments to one pipe and run the code received from another via eval, which is much faster.

The simplest script is:

#!/bin/sh

	printf ’0%s’ app "$@" > "${XDG_RUNTIME_DIR}/uwsm-app-daemon-in"
	IFS=’’ read -r cmd < "${XDG_RUNTIME_DIR}/uwsm-app-daemon-out"
	eval "$cmd"

Provided uwsm-app client script is a bit smarter: it can start the daemon, applies timeouts, and supports newlines in returned args.

SHELL PROFILE INTEGRATION

To launch uwsm automatically on login, add one of constructs below (or similar) to shell profile.

This asks to select a compositor (or refuse and continue with login shell) when logged in on VT 1:

			if uwsm check may-start && uwsm select; then

			exec systemd-cat -t uwsm_start uwsm start default
			fi

This just starts a specific compositor depending on foreground VT:

			if uwsm check may-start 1; then

			exec systemd-cat -t uwsm_start uwsm start sway.desktop
			elif uwsm check may-start 2; then

			exec systemd-cat -t uwsm_start uwsm start labwc.desktop
			fi

Using " uwsm check may-start " as a condition is essential , not only to prevent accidental startup attempts where they are not expected, but also since startup may involve sourcing shell profile, which might lead to nasty loops.

See check subcommand section for info on may-start checker.

exec allows uwsm to replace login shell in order to properly bind to user session and handle session termination.

" systemd-cat -t uwsm_start " (optional) executes the command given to it ( uwsm ) with its stdout and stderr connected to the systemd journal, tagged with identifier "uwsm_start". See systemd-cat(1) for more options.

USE INSIDE DESKTOP ENTRY

To launch uwsm from a display/login manager, " uwsm start " can be used inside Desktop Entries. Example /usr/local/share/wayland-sessions/my-compositor.desktop :

	[Desktop Entry]
	Name=My compositor (with UWSM)
	Comment=My cool compositor
	Exec=uwsm start -N "My compositor" -D mycompositor -C "My cool compositor" mywm
	DesktopNames=mycompositor
	Type=Application

Things to keep in mind:

	•		For consistency, command line arguments should mirror the keys of the entry
	•		Command in Exec= should start with " uwsm start "
	•		It should not point to itself (as a combination of Desktop Entry ID and Action ID)
	•		It should not point to a Desktop Entry ID and Action ID that also uses ‘uwsm‘

Potentially such entries may be found and used by uwsm itself, i.e. in shell profile integration situation, or when launched manually. Following the principles above ensures uwsm will properly recognize itself and parse requested arguments inside the entry without any side effects.