Q&A for How to Access Windows Files in Ubuntu

The location will not always be /dev/sda2. It may be something else on your system. You will need to look at GPartEd in order to figure out what you need to type in for the mount command. Also, you put an extra '/' in /dev/sda2 right before the 2. This may have affected your mount command as well.

It means something else is already accessing the volume. Make sure that no other programs are using the volume and try again.

You will have to change your root password. The root password is typically the administrator's login password. But if it's not, you will have to change it by editing boot commands.

Try "sudo -s" instead of "su". "sudo -s" & "su" are related, but not identical. If you use "su", you'll be prompted for the "root" password. This method may not work, e.g., maybe your root account's password is disabled--or your system is configured to restrict who can become root with "su" (some configurations only allow members of a group called "wheel", for instance). If you use "sudo -s", you'll normally be prompted for your own password, instead. This method requires your account to be listed appropriately in the sudo configuration; but fortunately, the Ubuntu installation procedure usually sets up the sudo configuration automatically after it has you create your account.