I have a Raspberry Pi which was on a couple of hours ago, and the last thing I did was sudo apt-get upgrade. Then, I rebooted it, the Colour splash screen shows, seems like its booting fine and the Raspbian PIXEL logo shows leading to a black screen with a flashing cursor and nothing else. What could the problem be please?
Failed or incomplete upgrade is one of those rare cases where you may render Linux unbootable. This usually happens when several related packages (like kernel and kernel modules) are being upgraded, and the some package get upgraded while others don't. This can happen e.g. when you interrupt the process with Ctrl+C or run out of space.
If you're specifically interested to know what went wrong, I suggest you check files in
/var/lib/dpkg/ directory (starting with
status) for anomalies. If you just want to get your system running, the easiest way would be to back up your files and reinstall.