Background

I have an application that requires that I start several RViz windows in a headless ROS environment. The system is required to send image files to some locally networked dumb terminals which can barely but adequately show image files (.jpg). Therefore, I simply take screen snapshots of the RViz displays and send those. This works well, however, I need to run the RViz windows on startup.

Implementation

The ROS noetic system is running on Ubuntu 20.04. I used robotupstart to give me a working skeleton for a systemd service and then modified the core service file to allow displaymanager access

This is my working system.d service file called 'test.service' in /lib/systemd/system

[Unit]
Description="bringup test"
After=network.target
After=display_manager.service
Wants=display_manager.service

[Service]
Type=simple
Environment="XAUTHORITY=/run/user/1000/gdm/Xauthority"
Environment="DISPLAY=:0"
Environment="XDG_RUNTIME_DIR=/home/<my_username>/catkin_ws/tmp"
Environment="/home/<my_username>"    # THIS IS THE SOLUTION SOUGHT BY THIS QUESTION
ExecStart=/usr/sbin/test-start

[Install]
WantedBy=multi-user.target

This almost works. journalctl -f -u test.service lists an error:

Jun 06 21:10:22 aoede test-start[10209]: /opt/ros/noetic/lib/rviz/rviz: line 1: 10220 Aborted                 (core dumped) $0 $@
Jun 06 21:10:25 aoede dbus-daemon[10259]: [session uid=1000 pid=10257] AppArmor D-Bus mediation is enabled
Jun 06 21:10:28 aoede test-start[10237]: terminate called after throwing an instance of 'boost::filesystem::filesystem_error'
Jun 06 21:10:28 aoede test-start[10237]:   what():  boost::filesystem::create_directory: Permission denied: "/.rviz"
Jun 06 21:10:28 aoede test-start[10218]: Aborted (core dumped)

It is trying to write to a directory /.rviz . When I create this directory myself off the root directory with relaxed permissions it then works correctly and the RViz windows all start. This directory seems to be filled with persistence files for the RViz instances.

I have tried setting XDGRUNTIMEDIR as above but it had no effect. What environment variable should I set, or other way, so that RViz is looking in a more rational place? Also, would appreciate any recommendations on better practices than above.

void VisualizationFrame::initConfigs()
 {
   home_dir_ = QDir::toNativeSeparators(QDir::homePath()).toStdString();

   config_dir_ = (fs::path(home_dir_) / ".rviz").string();
   persistent_settings_file_ = (fs::path(config_dir_) / "persistent_settings").string();
   default_display_config_file_ = (fs::path(config_dir_) / "default." CONFIG_EXTENSION).string();
   ...

Under non-Windows operating systems the HOME environment variable is used if it exists, otherwise the path returned by the rootPath().

Environment="HOME=/home/<my_username>"

rosrun robot_upstart install --job test --user <my_username> --setup ~/catkin_ws/devel/setup.bash --rosdistro noetic --logdir ~/catkin_ws/.ros --provider systemd --symlink <my_package>/launch/test_start.launch