What Exactly Is Emergency Mode and How Can I Boot Into It?

You actually can't choose to boot into emergency mode on demand; it starts automatically when the system encounters a severe error that prevents it from mounting the root filesystem. But don't fret—all messages that say [FAILED] aren't always critical. Sometimes they can be safely ignored.

In emergency mode, your system boots partially and drops you into a command line instead of going all the way through the startup process. This would typically happen if essential parts of the system, like the root filesystem, can't be mounted properly. If your system is still booting, you can try accessing a TTY by using Ctrl-Alt-F1, F2, etc., instead of going directly to emergency mode. This could give you a chance to fix the issue without fully dropping into emergency mode.

Emergency mode is basically a failsafe option for your system. It kicks in when something critical fails during bootup, allowing you to troubleshoot the issue from a terminal. If you're facing specific problems, it would help to know what they are so we can guide you better.