Start an Electron app at boot on Raspberry Pi 3 with yocto - linux

Question

I built an image with X11 using yocto for a Raspberry Pi 3 and a touchscreen. I can start my app built with Electron (chromium) by running commands manually in a serial session:
export DISPLAY=:0
/usr/lib/node/electron/dist/electron --no-sandbox /home/root/app
I though to use an init.d script to do it automatically at startup but I'd like to do it the proper way. I tried to create an .Xsession file in my user directory with the commands above but it doesn't work and I don't know if I can get logs of what happened.
According to this wiki, there is a lot of steps at X11 startup. Currently, I only see a Terminal (from Matchbox I guess) and a mouse cursor.
What's the "standard" way to start an app with the system and is there a way to remove the cursor for a touchscreen?
Edit
Here is the content of my /etc/X11 directory:
Xsession
Xsession.d/
xinit/
xorg.conf
Xsession:
#!/bin/sh
if [ -x /usr/bin/dbus-launch ]; then
# As this is the X session script, always start a new DBus session.
eval `dbus-launch --sh-syntax --exit-with-session </dev/null`
echo "D-BUS per-session daemon address is: $DBUS_SESSION_BUS_ADDRESS"
fi
. /etc/profile
if [ -f $HOME/.profile ]; then
. $HOME/.profile
fi
SYSSESSIONDIR=/etc/X11/Xsession.d
export CLUTTER_DISABLE_MIPMAPPED_TEXT=1
for SESSIONFILE in $SYSSESSIONDIR/*; do
set +e
case "$SESSIONFILE" in
*.sh)
. "$SESSIONFILE"
;;
*.shbg)
"$SESSIONFILE" &
;;
*~)
# Ignore backup files
;;
*)
"$SESSIONFILE"
;;
esac
set -e
done
exit 0
xorg.conf: empty.
Xsession.d/:
13xdgbasedirs.sh
30xinput_calibrate.sh
89xdgautostart.sh
90XWindowManager.sh
89xdgautostart.sh:
XDGAUTOSTART=/etc/xdg/autostart
if [ -d $XDGAUTOSTART ]; then
for SCRIPT in $XDGAUTOSTART/*; do
CMD=`grep ^Exec= $SCRIPT | cut -d '=' -f 2`
$CMD &
done
fi
90XWindowManager.sh:
if [ -x $HOME/.Xsession ]; then
exec $HOME/.Xsession
elif [ -x /usr/bin/x-session-manager ]; then
exec /usr/bin/x-session-manager
else
exec /usr/bin/x-window-manager
fi
There is also a file /etc/xserver-nodm/Xserver:
#!/bin/sh
# This script is only needed to make sure /etc/X11/xserver-common
# can affect XSERVER, ARGS & DPI: otherwise systemd could just use
# /etc/default/xserver-nodm as EnvironmentFile and sysvinit could just
# source the same file
. /etc/profile
# load default values for XSERVER, ARGS, DISPLAY...
. /etc/default/xserver-nodm
# Allow xserver-common to override ARGS, XSERVER, DPI
if [ -e /etc/X11/xserver-common ] ; then
. /etc/X11/xserver-common
if [ ! -e $XSERVER ] ; then
XSERVER=$(which $XSERVER)
fi
fi
if [ -n "$DPI" ] ; then
ARGS="$ARGS -dpi $DPI"
fi
exec xinit /etc/X11/Xsession -- $XSERVER $DISPLAY $ARGS $*
and a file /etc/rc5.d/S09xserver-nodm:
#!/bin/sh
#
### BEGIN INIT INFO
# Provides: xserver
# Required-Start: $local_fs $remote_fs dbus
# Required-Stop: $local_fs $remote_fs
# Default-Start: 5
# Default-Stop: 0 1 2 3 6
### END INIT INFO
killproc() { # kill the named process(es)
pid=`/bin/pidof $1`
[ "$pid" != "" ] && kill $pid
}
read CMDLINE < /proc/cmdline
for x in $CMDLINE; do
case $x in
x11=false)
echo "X Server disabled"
exit 0;
;;
esac
done
case "$1" in
start)
. /etc/profile
#default for USER
. /etc/default/xserver-nodm
echo "Starting Xserver"
if [ "$USER" != "root" ]; then
# setting for rootless X
chmod o+w /var/log
chmod g+r /dev/tty[0-3]
# hidraw device is probably needed
if [ -e /dev/hidraw0 ]; then
chmod o+rw /dev/hidraw*
fi
fi
# Using su rather than sudo as latest 1.8.1 cause failure [YOCTO #1211]
su -l -c '/etc/xserver-nodm/Xserver &' $USER
# Wait for the desktop to say its finished loading
# before loading the rest of the system
# dbus-wait org.matchbox_project.desktop Loaded
;;
stop)
echo "Stopping XServer"
killproc xinit
sleep 1
chvt 1 &
;;
restart)
$0 stop
$0 start
;;
*)
echo "usage: $0 { start | stop | restart }"
;;
esac
exit 0

Answer 1

The correct way to define a complete X session depends on your session manager: on Yocto that is often matchbox-session or mini-x-session. From your description I'd guess you're using mini-x-session (it happens to start a terminal and a window-manager if session file is not found).
Quoting mini-x-session:
if [ -e $HOME/.mini_x/session ]
then
exec $HOME/.mini_x/session
fi
if [ -e /etc/mini_x/session ]
then
exec /etc/mini_x/session
fi
So adding a /etc/mini_x/session script should work.
By the way, in your session file you may also want to start a window manager (X can do weird things without one):
your-app-here &
exec matchbox-window-manager