=== Slow Query Logs ===
Checking the slow query logs via mysql prompt.
\\
\\Note: You CAN enable the slow query logging on runtime. A mysql restart will flush the changes made via runtime. If you wish for persistence then add it to the /etc/my.cnf file:
<sxh bash>
mysql> SHOW GLOBAL VARIABLES LIKE 'slow\_%';
+---------------------+-------------------------------+
| Variable_name       | Value                         |
+---------------------+-------------------------------+
| slow_query_log      | ON                            |
| slow_query_log_file | /path/to/slow_query.log       |
+---------------------+-------------------------------+
</sxh>
Set the logs to another path:
<sxh bash>
mysql> SET GLOBAL slow_query_log_file = '/path/to/slow_query.log'; 
</sxh>
<sxh bash>
mysql> SET GLOBAL slow_query_log = 'ON';
</sxh>
\\
Via the command line:
\\
\\
You can check to see if slow query logging is currently enabled. The following command assumes you have configured .my.cnf file:
<sxh bash>
show variables like "%slow%";
</sxh>
Or you can run the following from the command line:
<sxh bash>
mysql -e 'show variables;' | grep slow_query_log
</sxh>
Output should show something similar to:
<sxh bash>
+---------------------+---------------------------------+
| Variable_name       | Value                           |
+---------------------+---------------------------------+
| log_slow_queries    | OFF                             |
| slow_launch_time    | 2                               |
| slow_query_log      | OFF                             |
| slow_query_log_file | /var/run/mysqld/mysqld-slow.log |
+---------------------+---------------------------------+
</sxh>
Or:
<sxh bash>
slow_query_log  OFF
slow_query_log_file     /var/run/mysqld/mysqld-slow.log
</sxh>
\\
=== How many slow queries? ===
You can also use the following command to view if you currently have any slow queries (if logging has been enabled):
<sxh bash>
show status like '%slow%';
</sxh>
Or from the command line:
<sxh bash>
mysql -e 'show status;' | grep -i slow
</sxh>
This should produce a similar output:
<sxh bash>
Slow_launch_threads     0
Slow_queries    0
</sxh>
\\
----------------------------------------------------------------
=== Configuring Slow Query logs ===
\\
There are 2 options for configuring slow query logs:
\\
\\
-** Run time** - this will configure the slow query logs in the current runtime environment, when mysql is restarted the value will be lost. You will need to configure the value in the /etc/my.cnf for variables to remain
\\
\\
- **Permanent** - editing the /etc/my.cnf will allow mysql to retain the values once the service has been restarted. Changing this file will NOT change the current runtime environment. 
\\ 
\\
**__NOTE__**: To enable to variables without restarting the service, use a combination of both techniques above. 
\\
\\
=== Run-time Configuration ===
\\ If run the following command it will set slow query logging without needing to restart mysql
<sxh bash>
mysql -e 'set global log_slow_queries = 1;'
</sxh>
\\ You can now run the following command and it should produce an output saying that slow_query logging is enabled:
<sxh bash>
mysql -e 'show variables;' | grep slow
</sxh>
\\

=== /etc/my.cnf - Permanent Configuration ===
<sxh bash>
slow_query_log = 1
slow_query_log_file = /var/log/mysql/slow.log
long_query_time = 10
log_queries_not_using_indexes = 1
</sxh>
**Note**: Change permissions so that mysqld can write to the specified log file. Giving write permissions to the 'other' group should suffice.