Errors "Invalid (old?) Table Or Database Name 'lost+found'"; ignore-db-dir option Introduced in MySQL 5.6
Last updated on APRIL 13, 2017
Applies to:MySQL Server - Version 5.5 and later
Information in this document applies to any platform.
Certain filesystems use the 'lost+found' directory as the partitions cleanup directory for managing corrupted inodes, file recovery etc. Common examples are the ext3 filesystem on Linux.
On : 5.1, 5.5, 5.6 version, Other Technical Problem
SHOW DATABASES indicates a database named 'lost+found' which is not a real database. Any other directory under the data directory will also be treated as a database. You will also see errors like these in the error log file:
[ERROR] Invalid (old?) table or database name 'lost+found'
[ERROR] Invalid (old?) table or database name 'anyotherdirectory'
SHOW DATABASES should indicate all the valid MySQL databases, not extraneous ones.
The issue can be reproduced at will with the following steps:
1. Create a partition which has managed cleanup using 'lost+found' directory such as ext3.
2. Set the MySQL datadir option to be the new partition mount point e.g. /data
3. Run SHOW DATABASES within the MySQL client to see the 'lost+found' database show up.
The issue has the following business impact:
Due to this issue, users can be distracted as to what is a real database and what is a system directory. There are no other adverse effects.
Move the datadir to a new partition or to a directory below the root level. For other directories being treated as databases, move them out of the data directory tree.
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