La La Lab scripts

These scripts are used on certain interactive stations at the exhibition “La La Lab – the Mathematics of Music”.

Installation

La La Lab OS

The target system for running the script is Ubuntu 18.04.2 provided that the following settings have been applied during installation:

Choose minimal installation
Install third-party software for graphics and WiFi hardware... : ON
Configure secure boot: ON. (set a password; it needs to be entered on first boot)
Account settings:
- User name: lalalab
Reboot after installation is complete
Enroll the secure boot keys using the password you entered during secure boot configuration
Reboot into the system

Bootstrapping

The script bin/bootstrap-lalalabos will install required packages, the scripts in this repository as well as most of the exhibits:

wget https://raw.githubusercontent.com/IMAGINARY/lalalab-scripts/master/bin/bootstrap-lalalabos
chmod +x bootstrap-lalalabos
sudo ./bootstrap-lalalabos

Some changes made by the bootstrapping script might only take effect after a reboot.

Immutable file system

The bootstrapping script will ask if it should make the file system immutable after next reboot. This can be very useful to make the whole setup immune to crashes or other modifcations of the system. So even if something goes severely wrong during operation, a reboot will usually solve all problems because it resets the system to a well defined state.

The immutable file systems is achieved via overlayroot which writes file modifications to a tmpfs in RAM instead of the local hard disk. Programs that write a lot of data might cause problems since available RAM might be limited.

Immutability can be toggled using the scripts enable-overlayroot and disable-overlayroot. Both require a reboot to take effect.

In immutable mode, changes to the local file system can be performed via the overlayroot-chroot command but this might have unintented consequences since not all system modifications (such as modifications to the bootloader or systemd) work well from within a chroot. So handle with care.

Updating

You can either re-run bootstrap-lalalabos or reinstall/update individual exhibits via the install-* scripts. Note that in most cases, install-lalalab-scripts must be executed first to update the other installation scripts to the most recent version.

Uninstalling

It is out of the scope of these scripts to provide facilities for uninstalling. You have to check the installation scripts to figure out how to roll back an installation manually.

Doing so might also be helpful in cases where installations or updates fail. Cleaning previous installations might fix certain issues.

Starting exhibits

Exhibit start script names are prefixed with exhibt- followed by an identifier of that exhibit. See bin for a list of known exhibits.

Restart exhibits after a crash

The script repeat-exhibit will restart the executable supplied as argument indefinitely, e.g.

repeat-exhibit exhibit-kiosk

will restart exhibit-kiosk if it exits for whatever reason.

Stopping exhibits

All exhibits can be stopped via

stop-exhibits

This includes the repeat-exhibit script and any process whose name starts with exhibit-.

Autostart

By default, an openbox session is started that first runs an init script for the exhibit and then runs the exhibit in a loop with mouse cursor hiding enabled.

The init script is supposed to run only once and it needs to exit once the init tasks are performed. Otherwise, script execution will block and no exhibit will be started.

By default, init scripts and exhibits are selected via the host name of the system (see bin/get-default-exhibit-by-hostname). It is possible to override this behavior to allow for user-defined exhibits. If the following executables are present, they will be run instead of the system-wide default:

~/.exhibition/default-init
~/.exhibition/default-exhibit

Note that these executables can be scripts themselves or just symlinks to one of the init-* respectively exhibit-* scripts. If no special initialization is needed, you can just create a symlink to true:

ln -s `which true` ~/.exhibition/init-default

Additional notes on some of the scripts

Hide the cursor

The script hidecursor hides the cursor and starts another child process supplied as an argument. When the child exits, the cursor will not be hidden anymore.

Fake display resolution for testing

Sometimes the display used for development does not match the resolution used in production. Assume your test display has a default resolution of 1920x1080 (FullHD), but in production, 3840x2160 (UHD) is used. The command

fakeResolution 3840x2160

will allocate a 3840x2160 frame buffer and will scale it down to 1920x1080.

If aspect ratios do not match, the image will be stretched.

malex984/lalalab-scripts