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MySQL Enterprise Backup 4.1 User's Guide
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5.1 Performing a Restore Operation

The mysqlbackup commands to perform a restore operation are copy-back-and-apply-log and copy-back (for directory backup only; see Section 5.1.7, “Advanced: Preparing and Restoring a Directory Backup”). Normally, the restoration process requires the database server to be already shut down (or, at least not operating on the directory you are restoring the data to), except for restorations of backups created with the --use-tts option; see explanations below. The process copies the data files, logs, and other backed-up files from the backup directory back to their original locations, and performs any required post-processing on them.

Example 5.1 Restoring a Database

mysqlbackup --defaults-file=<my.cnf> -uroot --backup-image=<image_name> \
  --backup-dir=<backupTmpDir> --datadir=<restoreDir> copy-back-and-apply-log

The copy-back-and-apply-log command achieves two things:

  • Extracts the backup from the image file and copies it to the data directory on the server to be restored.

  • Performs an apply log operation to the restored data to bring them up-to-date.

See Section 4.2.4, “Restoring a Database” for an explanation of the important options used in a restore operation like --defaults-file, --datadir, --backup-image, and --backup-dir.

The restored data includes the backup_history table, where MySQL Enterprise Backup records details of each backup. The table allows you to perform future incremental backups using the --incremental-base=history:{last_backup | last_full_backup} option.

  • When performing a restore, make sure the target directories for restore data are all clean, containing no old or unwanted data files (this might require manual removal of files at the locations specified by the --datadir, --innodb_data_home_dir, --innodb_log_group_home_dir, and --innodb_undo_directory options). The same cleanup is not required for restoring backups created with the--use-tts option (in which case other requirements described in Section 5.1.4, “Restoring Backups Created with the --use-tts Option” apply though).

  • After a full restore, depending on how you are going to start the restored server, you might need to adjust the ownership of the restored data directory. For example, if the server is going to be started by the user mysql, use the following command to change the owner attribute of the data directory and the files under it to the mysql user, and the group attribute to the mysql group.

    $ chown -R mysql:mysql /path/to/datadir
  • Because mysqlbackup does not support MySQL server's online DDL feature feature, a backup might become corrupted if, during the backup process, a DDL operation that took advantage of the feature occurred. To avoid the issue, mysqlbackup turns the server's system variable old_alter_table to 1 at the beginning of a backup if it is 0, so that any DDL operations that take place during the backup are handled with the old table copy method. mysqlbackup then turns the variable back to 0 near the end of the backup operation.

    Notice that in cases where mysqlbackup quits unexpectedly and does not turn old_alter_table back to its original value, the user will have to turn the value back to 0 manually on the server, in order to return the server to its original configuration. This should be performed if the statement Server system variable 'old_alter_table' was set to '0'. Setting it to '1' appears in the early output of mysqlbackup, but the statement Setting server system variable 'old_alter_table' back to '0' does not appear before mysqlbackup quits.

The following subsections describe a number of different scenarios for restoring a backup.