"Macintosh HD" partition got partially corrupted, and Disk Utility cannot repair it. A lot of files are still in good condition, I want to backup them using Ubuntu LiveCD. But there is a problem: I don't have permission to access the files, because default ubuntu UID and mac files UID do not match. And I cannot change the ubuntu UID in LiveCD mode. So, I must change the UID of Mac files to ubuntu UID. Please tell me, how to do it?