View source for Howto/20120923 Repair corrupt MySQL database that won't start

'''Sources''': 
* http://dev.mysql.com/doc/refman/5.0/en/myisamchk.html
* http://dba.stackexchange.com/questions/23361/innodb-force-recovery-when-innodb-corruption

'''Steps'''
* Always check log files first for suggestions, /var/log/mysql/
* Try to repair the database offline, in a shell run:
<pre>
sudo myisamchk --force --update-state --key_buffer_size=64M \
--sort_buffer_size=64M --read_buffer_size=1M \
--write_buffer_size=1M /var/lig/mysql/*/*.MYI
</pre>
* Reboot and test that the database is online.
* If database still offline, edit /etc/mysql/my.cnf, and add the following line to section [mysqld]
<pre>
innodb_force_recovery = 6 # Should try 1 to 6 in increasing numbers
</pre>
* Reboot and test that the database is online. Note: Database should be online but the innoDB is still corrupt and must be fixed!
* Create a dump of the sql database
<pre>
sudo mysqldump -u root -p--all-databases > ~/backup.sql
</pre>
* Delete the ibdata and ib_logfile files
<pre>
sudo rm /var/lib/mysql/ibdata1
sudo rm /var/lib/mysql/ib_logfile*
</pre>
* Remove the recovery mode, by commenting the previously added line:
<pre>
# innodb_force_recovery = 6 # Should try 1 to 6 in increasing numbers
</pre>
* Reboot and test that the database is online.
* Restore the dump
<pre>
sudo mysql -u root -p < ~/backup.sql
</pre>
or from mysql:
<pre>
mysql> source backup.sql
</pre>