Here are useful tips I found when dealing with MySQL servers.
Repairing crashed tables
Sometimes a MySQL utility will report an error such as:
Got error: 145: Table '<tablename>' is marked as crashed and should be repaired when using LOCK TABLES
You can check the index files using the myisamchk utility,
cd /var/lib/mysql/<dbname> myisamchk -e *.MYI
which should show an output similar to:
Checking MyISAM file: <tablename>.MYI Data records: 130 Deleted blocks: 0 myisamchk: warning: Table is marked as crashed - check file-size - check record delete-chain - check key delete-chain - check index reference - check data record references index: 1 - check data record references index: 2 - check data record references index: 3 - check records and index references MyISAM-table '<tablename>.MYI' is usable but should be fixed
No errors reported
In this case, the table is fine, but just marked as crashed. Make sure the MySQL server is stopped
and then use myisamchk to mark the table is ok.
myisamchk --update-state <tablename>.MYI
You can then restart MySQL
If the index file is actually corrupt, but the data is ok, the index file can be rebuilt:
myisamchk -r -q <tablename>
Full details are available on the MySQL website: 5.6.3. How to Repair MyISAM Tables