I have Linux Mint 17.3 on VM Virtual Box. Unfortunately, I forgot my username and password. Can someone tell me the steps on how to reset my username and password?
You could boot it into single user mode (if you don't know how to do it, just Google it) then enter this command:
mount -uw /
(In some cases, this command varies from system to system, so you may have to try some other command to make the filesystem writeable.)
passwd then type what you want 'the root password' to be (just make sure it's a very secure password!) Then 'the root user' will be enabled, then log into 'root' then you'll have admin privileges and you can then reset your password, but while logged in as root, be careful, because while you're root, you have infinite privilege on the computer and you could easily accidentally delete an important system file without it even asking 'are you sure'.