I wonder why mount command takes file system type option like "mount -t type ...". It can find out device's file system type and choose related parameter. Is it possible to mount disks with a file system type other than its current fstype? For example, disk table says sda1's file system type is linux(ext3) but it is real fstype is ntfs, so we use "mount -t ntfs ..." to mount it, is it possible?
2 Answers
The "automagic" filesystem detection feature of mount is nice, but will probably not detect every filesystem that Linux supports.
And you need the -t parameter to mount network filesystems like NFS and CIFS.
The mount auto probing technique uses a heuristic (the presence of appropriate 'magic'), and could recognize the wrong filesystem type, possibly with catastrophic consequences. If your data is valuable, don't ask mount to guess. This also applies to trying to force the wrong fs mount type, mainly due to the different way each fstype is handled (including structural differances).
