Trouble Starting Linux Due to Full Hard Drive

I was having a similar problem! What helped me was running the `rm` command manually in the terminal to delete the files I didn't need, so I'd recommend giving it a try. Just be super careful with it, as you can easily delete important files if you're not sure what you're removing. Always double-check the path before you hit enter!

The black screen with a blinking cursor could indicate that your Nvidia drivers aren't set up correctly. Try booting with the `nomodeset` option in GRUB to see if that helps you access the system without graphical mode issues.

It sounds like you're running into permission issues. If you're in a Live USB environment, try using a root shell. Usually, you can get root access by simply using the `sudo` command before your mounting commands. If the USB doesn't require a password, you might not need to enter anything. If 'mount' fails, it might mean your drive is in use or has issues.

To start managing your files, open a terminal and identify your partitions using the command `lsblk`. Once you know which partition is your main drive (probably `sda2`), you can create a backup directory and mount it using `mkdir backup` and `mount /dev/sdaX backup`. You should be able to navigate and delete files from there. Just make sure you replace `sdaX` with the correct drive number you found.