Help please! I'm very new to linux and ubuntu. I just got an Acer netbook Aspire One. I put the Ubuntu remix on it successfully, and was using it for several days without problems. Now all of a sudden when I turn on my computer I get a grub error message with a command prompt. I've tried following the direction to restore grub but I'm getting stuck right away on the command to mount my ubuntu partition. After I type "sudo mount /dev/sda4 /mnt", I keep getting the error message "mount: you must specify the filesystem type." I can't figure out what to do next?