============================
 Frequently Asked Questions
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Do I need an InnoDB Hot Backup license to use Percona XtraBackup?
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No. Although ``innobackupex`` is derived from the same GPL and open-source wrapper script that InnoDB Hot Backup uses, it does not execute ``ibbackup``, and the ``xtrabackup`` binary does not execute or link to ``ibbackup``. You can use |Percona XtraBackup| without any license; it is completely separate from InnoDB Hot Backup.

Why is innobackupex distributed as innobackupex-1.5.1?
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That's the way the source for the tool was distributed from Oracle. Nowadays, it is a symbolic link to |innobackupex| for backward compatibility with |Percona XtraBackup|.

What's the difference between :program:`innobackupex` and :program:`innobackup`?
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Because :program:`innobackupex` is a patched version of *Oracle* ’s :program:`innobackup` script (now renamed to :program:`mysqlbackup`), it is quite similar in some ways, and familiarity with innobackup might be helpful.

Aside from the options for specific features of |innobackupex|, the main differences are:

  * printing to ``STDERR`` instead of ``STDOUT`` (which enables the :option:`--stream` option), 

  * the configuration file - :term:`my.cnf` - is detected automatically (or setted with :option:`innobackupex --defaults-file`) instead of the mandotory first argument,

  * and defaults to |xtrabackup| as binary to use in the :option:`--ibbackup`.

..  * Ssleep and compress?

See :doc:`innobackupex/innobackupex_option_reference` for more details.


Why doesn't the :program:`xtrabackup` binary include MyISAM tables and other files in its backup? Should I use :program:`innobackupex` always?
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:program:`xtrabackup` is a C program written to take advantage of the InnoDB or XtraDB features in order to make it as fast, less resource-consuming and unobtrusive (locking the database server) as possible. That is only possible with those engines. In the case of MyISAM a "read lock" is needed.

:program:`innobackupex` is a script written in Perl which wraps :program:`xtrabackup` and other backup tools (such as :program:`tar4ibd`) and provides you with the functionality of each tool taking care of the details.

However, for some specific tasks, you must use :program:`xtrabackup` directly. See the :ref:`user-manual` for details on each one.

Are you aware of any web-based backup management tools (commercial or not) built around |Percona XtraBackup|?
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`Zmanda Recovery Manager <http://www.zmanda.com/zrm-mysql-enterprise.html>`_ is a commercial tool that uses |Percona XtraBackup| for Non-Blocking Backups: 

 *"ZRM provides support for non-blocking backups of MySQL using |Percona XtraBackup|. ZRM with |Percona XtraBackup| provides resource utilization management by providing throttling based on the number of IO operations per second. |Percona XtraBackup| based backups also allow for table level recovery even though the backup was done at the database level (needs the recovery database server to be |Percona Server| with XtraDB)."*

|xtrabackup| binary fails with a floating point exception
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In most of the cases this is due to not having install the required libraries (and version) by |xtrabackup|. Installing the *GCC* suite with the supporting libraries and recompiling |xtrabackup| will solve the issue. See :doc:`installation/compiling_xtrabackup` for instructions on the procedure.

How innobackupex handles the ibdata/ib_log files on restore if they aren't in mysql datadir?
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In case the ibdata and ib_log files are located in different directories outside of the datadir, you will have to put them in their proper place after the logs have been applied.

Backup fails with Error 24: 'Too many open files'
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This usually happens when database being backed up contains large amount of files and |Percona XtraBackup| can't open all of them to create a successful backup. In order to avoid this error the operating system should be configured appropriately so that |Percona XtraBackup| can open all its files. On Linux, this can be done with the ``ulimit`` command for specific backup session or by editing the :file:`/etc/security/limits.conf` to change it globally (**NOTE**: the maximum possible value that can be set up is 1048576 which is a hard-coded constant in the Linux kernel). 
