1. Create user service in user's home directory ex. /home/<app_user>/.config/systemd/user/

Example:

[Unit]
Description=my npm app
After=network.target
 
[Service]
ExecStart=/usr/bin/npm start
WorkingDirectory=/home/debian/mynpmapp/
Restart=on-failure
 
[Install]
WantedBy=default.target

2. Enable service

systemctl --user enable mynpmapp.service

3. From root enable lingering so that it persists over reboots and logouts

loginctl enable-linger username

4. Use systemctl –user start|stop <servicename> to run service

apt install dbus-user-session

In .bashrc of the user put:

export XDG_RUNTIME_DIR=/run/user/$(id -u)
export DBUS_SESSION_BUS_ADDRESS="unix:path=${XDG_RUNTIME_DIR}/bus"

then logout and login again. If its still not working and you get na error

Failed to connect to bus: No such file or directory

try rebooting the server.

• Debian 10

• https://wiki.archlinux.org/index.php/Systemd/User#Automatic_start-up_of_systemd_user_instances
• https://serverfault.com/questions/841099/systemd-grant-an-unprivileged-user-permission-to-alter-one-specific-service
• https://serverfault.com/a/1047069/353235
• https://unix.stackexchange.com/questions/434494/how-do-i-setup-user-autostart-and-properly-configure-systemd-user-services/434647#434647