File systems like UFS or ZFS store file and directory names in the character set you use. If you use non-UTF-8 locales or mount a non-UTF-8 file system and move to a UTF-8 locale, you might see garbage characters in the file names. To fix this problem, use convmv(1) can be used to convert a single file name, a directory tree and the contained files or a whole file system into a different encoding. It only converts the file names, not the contents of the files.
See the convmv(1) man page for more information. The tool works on any file system.
Alternatively, fsexam(1) can be used for this purpose. For more information, see File Examiner (fsexam).