Here are some brief instructions for stuff that I can never remember how to do.
You can enable the GRUB boot menu by setting GRUB_TIMEOUT_STYLE=menu in /etc/default/grub and then update-grub
xset s $NSECONDS: Sets the timer for the screen to be deactivated to $NSECONDS.
Install chrony to sync the system clock. In some cases just installing will do it, you can start and enable the systemd daemon with systemctl enable chronyd.
man console_codes: Describes how to control the console with stdout. You can move the cursor around, set colors, stuff like that. Need for anything TUI based.
sudo fdisk -l: Lists mounted disk volumes. Useful for finding, for example USB flash drives.
dd bs=4M if=name_of_iso_file.iso of=/dev/sdX: Write an ISO file to the drive at /dev/sdX. (Unmount drive with umount first.)
ldconfig -p: Lists all libraries in library paths. For example do ldconfig -p | grep libsdl to find SDL libraries.
ldd: Lists all the libraries that the binary links to.
objdump -p: Lists all libraries that a binary links to among other things. Note you can also do ldd but this may result in code execution.
You can start a new X windows session from one of the other terminals (i.e. ctrl-alt-Fn by doing startx from that terminal.
Wayland is actually a protocol that's implemented by the desktop environments, so there is no equivalent to startx. You can try running it from e.g. GNOME by doing gnome-session --session gnome-wayland.
Run xev to get an interactive description of how inputs are referred to. Especially useful for binding events ot obscure keys.
Most programs seem to take their GUI settings from ~/.config/gtk-3.0/settings.ini. This settings here are referencing some stuff in ~/.config but mostly from /usr/share/themes. This is expected to contain a bunch of theme directories each of which has a shitload of settings for all sorts of different GUI programs.
Refer to dracula-gtk for a comprehensive example of what this should look like. My installer clones this directory when doing install(Programs.gtk) as sudo.
Multiple different GUI programs are used to set GUI settings in different contexts:
lxappearance: seems to set ~/.config/gtk-3.0/settings.ini.
qt5ct: Settings for stuff that uses Qt I guess.
kvantum: the GUI front-end is kvantummanager, this comes form KDE but may set some things, not too sure.
Most of these seem to ultimately take the cues from ~/.config/gtk-3.0/settings.ini so I think that in some cases this is all that's needed.
You can write a script in a language other than bash and make it executable. For example
#!/bin/bash
#=
exec julia --project --startup-file=no -q --compile=min -O0 "${BASH_SOURCE[0]}" "$@"
=#
println("what up!")gives minimal latency for Julia (short of actually compiling a binary).