~akopytov/percona-xtrabackup/xtrabackup-1.6-copy-diagnostics

:program:`innobackupex` is a script written in Perl that wraps the :program:`xtrabackup` and :program:`tar4ibd` binaries and performs the tasks where the performance and efficiency of *C* program isn't needed. In this way, it provides a convinient and integrated approach to backing up in many common scenarios.

The following describes the rationale behind :program:`innobackupex` actions.

.. _making-backup-ibk:

Making a Backup

===============

If no mode is specified, |innobackupex| will assume the backup mode.

By default, it starts :program:`xtrabackup` with the :option:`--suspend-at-end` option, and lets it copy the InnoDB data files. When :program:`xtrabackup` finishes that, :program:`innobackupex` sees it create the :file:`xtrabackup_suspended` file and executes ``FLUSH TABLES WITH READ LOCK``. Then it begins copying the rest of the files.

If the :option:`--ibbackup` is not supplied, |innobackupex| will try to detect it: if the :file:`xtrabackup_binary` file exists on the backup directory, it reads from it which binary of |xtrabackup| will be used. Otherwise, it will try to connect to the database server in order to determine it. If the connection can't be established, |xtrabackup| will fail and you must specify it (see :ref:`ibk-right-binary`).

When the binary is determined, the connection to the database server is checked. This done by connecting, issuing a query, and closing the connection. If everything goes well, the binary is started as a child process.

If it is not an incremental backup, it connects to the server. It waits for slaves in a replication setup if the option :option:`--safe-slave-backup` is set and will flush all tables with **READ LOCK**, preventing all |MyISAM| tables from writing (unless option :option:`--no-lock` is specified).

Once this is done, the backup of the files will begin. It will backup :term:`.frm`, :term:`.MRG`, :term:`.MYD`, :term:`.MYI`, :term:`.TRG`, :term:`.TRN`, :term:`.ARM`, :term:`.ARZ`, :term:`.CSM`, :term:`.CSV` and :term:`.opt` files.

When all the files are backed up, it resumes :program:`ibbackup` and wait until it finishes copying the transactions done while the backup was done. Then, the tables are unlocked, the slave is started (if the option :option:`--safe-slave-backup` was used) and the connection with the server is closed. Then, it removes the :file:`xtrabackup_suspended` file and permits :program:`xtrabackup` to exit.

It will also create the following files in the directory of the backup:

:file:`xtrabackup_checkpoints`

containing the :term:`LSN` and the type of backup;

:file:`xtrabackup_binlog_info`

containing the position of the binary log at the moment of backing up;

:file:`xtrabackup_binlog_pos_innodb`

containing the position of the binary log at the moment of backing up relative to |InnoDB| transactions;

:file:`xtrabackup_slave_info`

containing the MySQL binlog position of the master server in a replication setup via ``'SHOW SLAVE STATUS\G;'`` if the :option:`--slave-info` option is passed;

:file:`backup-my.cnf`

containing only the :file:`my.cnf` options required for the backup;

:file:`xtrabackup_binary`

containing the binary used for the backup;

:file:`mysql-stderr`

containing the ``STDERR`` of :program:`mysqld` during the process and

:file:`mysql-stdout`

containing the ``STDOUT`` of the server.

If the :option:`--remote-host` was set, |innobackupex| will test the connection to the host via :command:`ssh` and create the backup directories. Then the same process will be applied but the log will be written to a temporary file and will be copied via :command:`scp` with the options set by :option:`--scpopt` (``-Cp -c arcfour`` by default).

After each copy the files will be deleted. The same rationale is for the :option:`--stream` mode.

Finally, the binary log position will be printed to ``STDERR`` and |innobackupex| will exit returning 0 if all went OK.

Note that the ``STDERR`` of |innobackupex| is not written in any file. You will have to redirect it to a file, e.g., ``innobackupex OPTIONS 2> backupout.log``.

.. _copy-back-ibk:

Restoring a backup

==================

To restore a backup with |innobackupex| the :option:`--copy-back` option must be used.

|innobackupex| will read the read from the :file:`my.cnf` the variables :term:`datadir`, :term:`innodb_data_home_dir`, :term:`innodb_data_file_path`, :term:`innodb_log_group_home_dir` and check that the directories exist.

It will copy the |MyISAM| tables, indexes, etc. (:term:`.frm`, :term:`.MRG`, :term:`.MYD`, :term:`.MYI`, :term:`.TRG`, :term:`.TRN`, :term:`.ARM`, :term:`.ARZ`, :term:`.CSM`, :term:`.CSV` and :term:`.opt` files) first, |InnoDB| tables and indexes next and the log files at last. It will preserve file's attributes when copying them, you may have to change the files' ownership to ``mysql`` before starting the database server, as they will be owned by the user who created the backup.

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