This file contains information to start the mini instance of InnoDB during the --apply-log. This is NOT a backup of original my.cnf. The InnoDB configuration is read from the file backup-my.cnf created by innobackupex when the backup was made. innobackupex --apply-log uses InnoDB configuration from backup-my.cnf by default, or from innobackupex --defaults-file, if specified. InnoDB configuration in this context means server variables that affect data format, i.e. innodb_page_size, innodb_log_block_size, etc. Location-related variables, like innodb_log_group_home_dir or innodb_data_file_path are always ignored by innobackupex --apply-log, so preparing a backup always works with data files from the backup directory, rather than any external ones.
From the docs: http:// www.percona. com/doc/ percona- xtrabackup/ 2.2/xtrabackup- files.html
- backup-my.cnf
This file contains information to start the mini instance of InnoDB during the --apply-log. This is NOT a backup of original my.cnf. The InnoDB configuration is read from the file backup-my.cnf created by innobackupex when the backup was made. innobackupex --apply-log uses InnoDB configuration from backup-my.cnf by default, or from innobackupex --defaults-file, if specified. InnoDB configuration in this context means server variables that affect data format, i.e. innodb_page_size, innodb_ log_block_ size, etc. Location-related variables, like innodb_ log_group_ home_dir or innodb_ data_file_ path are always ignored by innobackupex --apply-log, so preparing a backup always works with data files from the backup directory, rather than any external ones.