20.11 Message Logging Options

mysqlbackup writes important progress and error information to the stderr stream. The information is often very valuable for tracking down problems that occur during an operation. Starting from MySQL Enterprise Backup 3.9, the output to the stderr stream is also saved to a log file by default (for most mysqlbackup operations), so that the error information can be easily accessed in any debug process.

The message logging works like a tee process on a Unix-like system, in which the output of a program is split to be both displayed and saved to a file. The log file thus produced is named in the following format: MEB_timestamp_operation.log, where operation is the mysqlbackup operation that was run (e.g., backup, apply-log, etc.), and timestamp is the date and time at which the operation was run. Here are some examples of names for the log files:


The following options control the message logging function:

  • --skip-messages-logdir

    Skip message logging. Logging is turned on by default (except for the list-image and validate operations; see the description for the --messages-logdir option for details), and it is turned off by this option.

  • --messages-logdir=path

    Command-Line Format --messages-logdir=PATH
    Type Directory name
    Default Value backup_dir/meta

    Specifies the path name of an existing directory for storing the message log. If the specified directory does not exist, message logging fails and returns an error message. When this option is omitted, the default directory of backup_dir/meta is used, where backup_dir is the directory specified with the --backup-dir option.


    Use this option to turn on message logging for the list-image and validate operations. Message logging is turned off by default for the two operations, because they do not modify any files and a message log is usually not required for debugging them. And because the default path name of backup_dir/meta is not meaningful for the two operations, this option is required for both turning on message logging and for supplying the path name of a directory in which to save the log file. However, if the --skip-messages-logdir option is also specified, it takes precedence and message logging is skipped.

The following are some examples showing how the message logging is controlled.

This creates a log file for the backup operation in the directory /home/backup_dir/meta due to the default settings:

mysqlbackup -uroot --port=3306 --backup-dir=/home/backup_dir backup

This skips message logging for the backup operation:

mysqlbackup -uroot --port=3306 --backup-dir=/home/backup_dir \
      --skip-messages-logdir backup

This creates a log file for the apply-log operation in an existing directory named /home/teelog_dir, rather than the default location:

mysqlbackup -uroot --port=3306 --backup-dir=/home/backup_dir \
      --messages-logdir=/home/teelog_dir apply-log

This creates a log file for the list-image operation in an existing directory named /home/teelog_dir:

mysqlbackup -uroot --port=3306 --backup-image=/backup/my.mbi \
--messages-logdir=/home/teelog_dir list-image