There would be nothing in Parallels that would cause that; it's just like running Ubuntu on a PC. There could be many reasons for a permission denied error for example:
• You are trying to list files in a directory that you don't have permission to read
• You are trying to manipulate a file that you don't have permission to write
• You are trying to interact with a a hardware device or system file
Try the following commands:
cd ~
ls
...this should ensure that you are in your home folder that you have permission to read and write to, then list the contents; there should be no cause for error there unless you've done something to your home folder with chown or chmod. System administration commands need to be preceded by sudo and a space, but be very careful with that as it's not for everyday use.
