As described in Section 5.2, “MySQL Server Logs”, MySQL Server can create several different log files to help you see what activity is taking place. However, you must clean up these files regularly to ensure that the logs do not take up too much disk space.
When using MySQL with logging enabled, you may want to back up and remove old log files from time to time and tell MySQL to start logging to new files. See Section 7.2, “Database Backup Methods”.
On a Linux (Red Hat) installation, you can use the
mysql-log-rotate script for this. If you
installed MySQL from an RPM distribution, this script should have
been installed automatically. Be careful with this script if you
are using the binary log for replication. You should not remove
binary logs until you are certain that their contents have been
processed by all slaves.
On other systems, you must install a short script yourself that you start from cron (or its equivalent) for handling log files.
For the binary log, you can set the
expire_logs_days system variable
to expire binary log files automatically after a given number of
days (see Section 5.1.4, “Server System Variables”). If you are
using replication, you should set the variable no lower than the
maximum number of days your slaves might lag behind the master. To
remove binary logs on demand, use the
BINARY LOGS statement (see
Section 220.127.116.11, “
PURGE BINARY LOGS Syntax”).
You can force MySQL to start using new log files by flushing the
logs. Log flushing occurs when you issue a
statement or execute a mysqladmin flush-logs,
mysqladmin refresh, mysqldump
--flush-logs, or mysqldump
--master-data command. See Section 18.104.22.168, “
Section 4.5.2, “mysqladmin — Client for Administering a MySQL Server”, and Section 4.5.4, “mysqldump — A Database Backup Program”. In
addition, the binary log is flushed when its size reaches the
value of the
A log-flushing operation does the following:
If binary logging (
is used, the server closes the current log file and opens a
new log file with the next sequence number.
If the server was started with the
--log-error option to cause the
error log to be written to a file, it renames the current log
file with the suffix
-old and creates a new
empty error log file.
The server creates a new binary log file when you flush the logs.
However, it just closes and reopens the general and slow query log
files. To cause new files to be created on Unix, rename the
current log files before flushing them. At flush time, the server
opens new log files with the original names. For example, if the
general and slow query log files are named
mysql-slow.log, you can use a series of
commands like this:
mv mysql.log mysql.oldshell>
mv mysql-slow.log mysql-slow.oldshell>
On Windows, use rename rather than mv.
At this point, you can make a backup of
mysql-slow.old and then remove them from
For older versions of MySQL, you cannot rename certain log files
on Windows while the server has them open. Before MySQL 5.0.17,
this restriction applies to all log files. You must stop the
server, rename the file, then restart the server to create a new
log file. From 5.0.18 on, the restriction applies only to the
error log file. To rename the error log file, a stop and restart
can be avoided by flushing the logs to cause the server to rename
the current log file with the suffix
create a new empty error log file.
To disable or enable general query logging for the current
connection, set the session
sql_log_off variable to