Especially when you move mysql from Window [see related] to Linux using the data file copy, you might face such and error telling you one of your table’s .frm file is not found.
In this case either of the two can solve the problem.
1. be aware that the .frm, for that matter both MDI and MYI files are case sensitive to linux – as it is for all files. So, if on windows you have test.frm and your application access them as TesT.frm, you may not have problem, but it is a major one on Linux.
2. The other is group and ownership issue, make sure the files are under mysql on both ownership and group – unless you have other configuration for that.
TO change ownership use
sudo chmod -R mysql /path/to/data/files
and for group
sudo chgrp -R mysql /path/to/data/files
Hope it would help somebody.