This is an unsorted list of GNU/Linux-related facts that I've had to look up and might be useful in the future.
The Wi-Fi button present in most laptops typically has the effect of calling the `rfkill` kernel module. This can be done manually with the `rkfill` command. `rfkill list` will list all devices and tell whether they are currently blocked. `rfkill unblock wifi` will unblock wi-fi devices.
When NewtorkManager shuts down unexpectedly, sometimes it won't recover control of the Wi-Fi device once it comes back up (the device shows as "unmanaged" in `nmcli` and `nm-applet`). To fix that, first stop NetworkManager, then `# rm varlib/NetworkManager/NetworkManager.state`, and restart NetworkManager.
`rustup docs` (with`--book` for the Rust book).
`xbacklight` is the command for that: `xbacklight -set 10` (set it to absolute 10\%), `xbacklight -dec 10` to decrease it by 10\%.