Comment 1 for bug 1272329

Note there's a very similar bug reported against MySQL: http://bugs.mysql.com/bug.php?id=22615

I.e. the server treats any directory as a database and that may cause issues if some directories (such as lost+found, .Trashes, etc.) are created by OS utilities rather than the server.

The suggested workaround for lost+found mentioned in that bug report would also eliminate the problem for XtraBackup. I.e. just make datadir a subdirectory of a mount rather than the top-level directory.

That bug was fixed only in 5.6 by introducing another server option, --ignore-db-dir.

I see 2 ways to fix this for XtraBackup:

1) Provide a way to exclude certain directories from the backup. Which has already been requested in bug #688717.
2) Read ignore_db_dir from my.cnf in server versions 5.6 and higher, and automatically exclude them from the backup.

Which makes this report essentially a request to implement #2.