Linux can read more file system types than probably any other OS on the planet. UFS isn't so much of a UNIX standard as it once was. For instance, there are several forms of UFS that the different flavors of BSD use. Solaris does use UFS but most larger Sun systems use software RAID so you wouldn't be able to stick a Sun disk used in a Solaris RAID configuration and access the file system. Most others use their own journaled file systems now, AIX uses JFS, IRIX uses XFS, etc, etc..