mysql_fix_extensions converts the extensions for MyISAM (or ISAM) table files to their canonical forms.

It looks for files with extensions matching any lettercase variant of .frm, .myd, .myi, .isd, and .ism and renames them to have extensions of .frm, .MYD, .MYI, .ISD, and .ISM, respectively. This can be useful after transferring the files from a system with case-insensitive file names (such as Windows) to a system with case-sensitive file names.

From MariaDB 10.4.6, mariadb-fix-extensions is a symlink to mysql_fix_extensions.

Invoke mysql_fix_extensions as follows, where data_dir is the path name to the MariaDB data directory.

mysql_fix_extensions data_dir