MySQL won't start, no log ins /var/logs/mysql*
As the log indicates, you might have changed the values of the following parameters:


key_buffer_size
read_buffer_size
sort_buffer_size
max_threads 


If you have changed one of these values, try to revert the change and start the MySQL server again.

If you have not changed the values, calculate the memory usage by:

key_buffer_size + (read_buffer_size + sort_buffer_size)*max_threads


If you find the system installed memory is sufficient, you need to check if there is a corrupted table in your databases:

[mysqld]
innodb_force_recovery = 6


Then, to find out which database table is corrupted:

# mysqlcheck --all-databases


Write down all the tables listed as corrupted, you have to export the corrupted tables by:

# mysqldump -u{username} -p{password} {database_name} {table_name} &gt; table_backup.sql


After that, you can drop the table in Mysql console:

Mysql&gt; drop table {corrupted_table_name};


Then, we have to change back the Mysql configuration:

[mysqld]
innodb_force_recovery = 0


The MySQL server should be able to start up with normal operation mode.

Next, we have to import the data of corrupted tables:

# mysql -u{username} -p{password} {database_name} &lt; table_backup.sql


If everything runs fine, you should have your table data back and working Mysql Server.

Reference: InnoDB table recovery step-by-step-guide