I don't know whether its normal or not but when I mount a filesystem(ext4 partition, USB, SD card etc) via command line, I can't unmount it because it says
target is busy
It is the bash process which is using/accessing it. So I have to kill it first and then only can unmount the drive. As you have guessed, when I kill the bash process the terminal shuts down.and I have to reopen the terminal and unmount the drive. Is it normal ? I don't remember it happening the last time I unmounted something.