I know this will sound like lots of other problems on here, but trust me that I have tried everything suggested in those posts, and I still can't recover full access to my machine.
The situation is that I installed Unbuntu (22.04) on an old (late 2014) Mac Mini. I set a root password and one on my user account. For various reasons, I didn't use the machine for over a year, and now I can't get in (well, I can, but not in any useful way). I have forgotten the passwords.
Now, it is not important what is on that machine, and I do not need to get access to anything on there, I am more than happy to completely blitz the machine and start again from scratch. I would just like to be able to use the computer again, and not have to but a new one.
So, obviously, I tried to re-install from a USB stick with Ubuntu live on there, so that I could re-install. I hold down various key combinations (Shift, Shift/Option(Alt), etc.) which switching on the machine and it doesn't give me either the Startup Manager screen or the GRUB screen. Instead all I get is a screen with an image of a lock (like a bug padlock icon) and a prompt for a password. I have no idea what this password is either. I can't remember at any point (ever) setting a firmware password. Nothing I have tried or see suggested anywhere else has resulted in a screen where I can do anything useful ike drop to a root prompt in single-user mode and remount the root filesystem so I can start resetting passwords. I have been trying passwords for two days solid...
Anyway, one potentially useful thing is that I did set the system up to auto-login on boot to my user-level (non-admin) account, so I can get logged in and see everything I need to and get to a CLI prompt. However, because I can't remember the password for that account, I can't sudo anything to help, and I can't su to root either because I can't remember that password either.
Does anyone have any suggestions as to what I can do. If it means disassembing that machine to get the HD out to reformat, that I am happy to do that. I would ust love to be able to get Ubuntu server running on the machine so that it's useful again!
Thanks in advance if you have read this and have any suggestions.
