mylvmbackup(1)
==============
Lenz Grimmer <lenz@grimmer.com>

NAME
----
mylvmbackup - a utility for creating MySQL backups using LVM snapshots


SYNOPSIS
--------
'mylvmbackup' [OPTIONS]


DESCRIPTION
-----------
mylvmbackup is a tool for quickly creating backups of MySQL server's data
files. To perform a backup, mylvmbackup obtains a read lock on all tables and
flushes all server caches to disk, makes an LVM snapshot of the volume
containing the MySQL data directory, and unlocks the tables again. The
snapshot process takes only a small amount of time. When it is done, the
server can continue normal operations, while the actual file backup proceeds.

The LVM snapshot is mounted to a temporary directory and all data is backed up
using the 'tar' program. By default, the archive file is created using a name
of the form 'backup-YYYYMMDD_hhmmss_mysql.tar.gz', where 'YYYY', 'MM', 'DD',
'hh', 'mm', and 'ss' represent the year, month, day, hour, minute, and second
of the time at which the backup occurred. The prefix 'backup', date format and
file suffix may be modified. The use of timestamped archive names allows you
to run mylvmbackup many times without danger of overwriting old archives.

Alternatively, instead of 'tar', you may use 'rsync'. This process is nearly
identical, with the exception that the file suffix is not used. Currently,
the rsync backup is primarily developed for performing local backups. You
can configure it for backing up to a remote rsync server, but this is not
fully tested in all possible configurations yet and may change at some point.

GENERAL HINTS
-------------
It is required to run mylvmbackup on the same host where the MySQL server
runs. If your MySQL daemon is not listening on localhost or using the default
socket location, you must specify '--host' or '--socket'. Even though
mylvmbackup communicates with the server through a normal client connection to
obtain the read lock and flush data, it performs the actual backup by
accessing the file system directly. It is also a requirement that the MySQL
server's data directory resides on an LVM volume. (It is, however, a good idea
to do the LVM backup to a different partition than the one where the data
directory resides.  Otherwise, there is a good chance that LVM will run out of
undo space for LVM snapshot maintenance and the backup will fail.)

The user who invokes mylvmbackup must have sufficient filesystem permissions
to create the LVM snapshot and mount it. This includes read/write access to
the backup directory.

If you plan to back up InnoDB tables using LVM snapshots, be advised that it
is not sufficient to lock the tables and issue the 'FLUSH TABLES' command to
get the table files into a consistent state. When starting the MySQL server
from these restored files, InnoDB will detect these tables as being in an
inconsistent state and will perform a recovery run before the tables can be
accessed again. As this can potentially take some time (which you may not want
to spend after restoring a server and trying to get it back on its feet as
fast as possible), consider using the option '--innodb_recover', which will
perform the recovery operation on the backup snapshot prior to archiving it.

The recovery operation is performed by spawning a second mysqld instance that
uses the snapshot volume as the data directory. Note that this functionality
currently assumes the default InnoDB configuration - it does not work properly
if you use options like '--innodb-file-per-table', '--innodb-data-home-dir',
'--innodb-data-file-path' or '--innodb-log-group-home-dir' that modify the
default file layout for InnoDB tables.

Also note that this only works when using writable LVM snapshots and thus
requires LVM2 (the script performs a test for this and will disable log
recovery in the case it finds an LVM1 system). This will prolong the time
needed to perform the actual backup, but will save you precious time when you
eventually have to restore from this backup set.

If you use InnoDB tables exclusively, you may also want to consider to include
the option '--skip_flush_tables', to avoid the probably time-consuming and in
this case unnecessary flushing of buffers. But don't enable this option when
MyISAM tables are involved!


HOOKS
-----
It is possible to run arbitrary external programs or scripts (hooks) at
various stages of the backup process, to perform additional actions as part
of the backup process.

These scripts or symbolic links to executables should be placed in the
directory that the 'hooksdir' configuration option points to
('/usr/share/mylvmbackup' by default). They should return zero upon successful
completion, any non-zero return value will be considered a failure which will
be logged.

The names of the scripts or symbolic links reflect the stage in which the hook
will be called. Currently, the following stages exist:

* 'preconnect': before a connection to the database server is established
* 'preflush': before calling FLUSH TABLES
* 'presnapshot': before the file system snapshot is created
* 'preunlock': before the database tables are unlocked again
* 'predisconnect': before the connection to the database server is released
* 'premount': before the snapshot volume is mounted
* 'prebackup': before the snapshot backup will be performed
* 'precleanup': before the snapshot is unmounted and discarded

These hooks are optional and will only be called if a file for the particular
stage exists and is executable.  The execution of all hooks can be supressed
by passing the '--skip_hooks' option or by setting the 'skip_hooks'
configuration option to '1';

OPTIONS
-------
mylvmbackup supports the following command line options. The same options can
also be defined in the '/etc/mylvmbackup.conf' configuration file (omitting
the leading dashes, of course).

--user=string::
  Specifies the username to use for connecting to the MySQL server.
  The default is 'root'.

--password=string::
  Specifies the password to use for connecting to the MySQL server.
  The default is the empty string (no password).

--host=string::
  Specifies the host name to use for connecting to the MySQL server.
  The default is the empty string.

--port=number::
  Specifies the TCP port number to use for connecting to the MySQL server.
  The default is '3306'.

--socket=string::
  Specifies the path to the local socket file, if it is not located at the
  default location.
  The default is the empty string.

--innodb_recover::
  Run InnoDB recovery on the writable snapshot (LVM2 only)
  prior to performing the backup.

--skip_flush_tables::
  Don't issue a 'FLUSH TABLES WITH READ LOCK' command before creating the
  snapshot. Only use this option when backing up InnoDB tables (as they
  don't support this function anyway and will require recovery in any case).
  This option skips the (probably time consuming) flushing of buffers.

--extra_flush_tables::
  If your database performs a lot of writes, it may help to perform an extra
  initial 'FLUSH TABLES' so that the 'lvcreate' can finish within the
  interactivity timeout during the read-locked flush.

--pidfile=string::
  Specifies the full path and file name to the PID file of the server instance
  that is spawned to perform the InnoDB recovery (see option
  '--innodb_recover'). Must be different from the PID file that the actual
  running server uses.
  The default is '/var/tmp/mylvmbackup_recoverserver.pid'

--lvcreate=string::
  Specifies the pathname for the 'lvcreate' program.
  The default is 'lvcreate'.

--lvremove=string::
  Specifies the pathname for the 'lvremove' program.
  The default is 'lvremove'.

--lvs=string::
  Specifies the pathname for the 'lvs' program.
  The default is 'lvs'.

--mysqld_safe=string::
  Specifies the pathname for the 'mysqld_safe' program.
  The default is 'mysqld_safe'. 
  Only used to perform InnoDB recovery.

--mycnf=string::
  Specifies the name of the MySQL config file to include in the backup.
  The default is '/etc/my.cnf'.

--skip_mycnf::
  Skip backing up the MySQL configuration file.
  The default is to include a copy of the configuration file in the backup.

--hooksdir=string::
  The location of external scripts or executable to be called during various
  stages of the backup. See the HOOKS section in this manual page for more
  info.
  The default is '/usr/share/mylvmbackup'.

--skip_hooks::
  Skip invoking any external hooks during the backup.

--vgname=string::
  Specifies the volume group of the logical volume where the MySQL
  data directory is located.
  The default is 'mysql'.

--lvname=string::
  Specifies the name of the logical volume where the MySQL data
  directory is located.
  The default is 'data'.

--backuplv=string::
  Specifies the name of the logical volume for the snapshot volume.
  The default is appending "_snapshot" to the lvname.

--relpath=string::
  Relative path on the logical volume to the MySQL data directory.
  The default is the empty string.

--lvsize=string::
  Specifies the size for the snapshot volume.
  The default is '5G' (5 gigabytes).

--backuptype=string::
  Specifies what type of backup to perform. The available options are 'tar'
  and 'rsync'.

--prefix=string::
  Prefix added to the backup file names. It is also appended to
  the name of the directory used to mount the snapshot volume.
  The default value is 'backup'.

--datefmt=string::
  Format of the time stamp included in the backup file name. See
  the 'Date::Format' perldoc page for a description of the format.
  The default value is '%Y%m%d_%H%M%S', which creates a time stamp
  like 'YYYYMMDD_HHMMSS', e.g. '20070531_112549'

--mountdir=string::
  Path for mounting the snapshot volume to.
  The default value is '/var/tmp/mylvmbackup/mnt/'.

--backupdir=string::
  Specifies the pathname of the directory where the archive files will be
  written to. The backup directory must not be on the same volume as the MySQL
  data directory. Instead of a local directory, you can also provide a
  valid rsync URL here, e.g. 'hostname::rsync-module/path'. This requires a
  properly configured remote rsync setup (e.g. pre-setup SSH keys and a
  valid rsyncd.conf file). Note that using rsync for remote backups is still
  under development and the way to configure it may change!
  The default is '/var/tmp/mylvmbackup/backup/'

--mount=string::
  Specifies the pathname for the 'mount' program.
  The default is 'mount'.

--umount=string::
  Specifies the pathname for the 'umount' program.
  The default is 'umount'.

--tar=string::
  Specifies the pathname for the 'tar' program.
  The default is 'tar'.

--tararg=string::
  Specifies the initial arguments for the 'tar' program.
  The default is 'cvzf'.

--tarsuffixarg=string::
  Specifies the suffix arguments for the 'tar' program.
  The default is ''. 
  To exclude a database, you would pass '--exclude dbname' here.

--tarfilesuffix=string::
  Specifies the suffix for the tarball.
  The default is '.tar.gz'.

--rsync=string::
  Specifies the pathname for the 'rsync' program.
  The default is 'rsync'.

--rsyncarg=string::
  Specifies the arguments for the 'rsync' program.
  The default is '-avWP'. Should must ensure that the recursive option is
  included either implicitly by '-a', or explicitly.

--xfs::
  Use the 'nouuid' mount option to safely mount snapshot partitions that
  use the XFS file system.
  
--log_method=string::
  How to log output from this script. Valid options are 'console', 'syslog'
  or 'both'.
  The default value is 'console'.

--syslog_socktype=string::
  What type of socket to use for connecting to the syslog service. Valid
  options are 'native', 'tcp' and 'udp'.
  The default value is 'native'.

--syslog_facility=string::
  Define a particular syslog facility
  Default value is the empty string.

--syslog_remotehost=string::
  Host name of a remote syslog server.

--configfile=string::
  Specify an alternative configuration file.
  The default is '/etc/mylvmbackup.conf'.

--help::
  Displays a help message showing the available options.


FILES
-----
/etc/mylvbackup.conf::
  The 'mylvmbackup' configuration file
mylvmbackup::
  The executable Perl script that performs the work.


REQUIREMENTS
------------
For proper operation 'mylvmbackup' requires Perl 5 with the 'DBI' and
'DBD::mysql' modules. It also needs the 'Config::IniFiles' to read the global
configuration file of the program and 'Sys::Syslog' in case you want to enable
the syslog log facility. 'Date::Format' is required to create the time stamp
used in the backup file names. In addition, it utilizes 'Getopt::Long',
'File::Basename' and 'File::Temp', which usually are part of the default Perl
distribution.

It also requires several other external programs: GNU 'tar' and 'gzip' to back
up the data, LVM utilities ('lvcreate', 'lvremove' and 'lvs') to create and
remove the LVM snapshot, and the system utilities 'mount' and 'umount'.

'rsync' may be used in place of 'tar' and 'gzip'.

SEE ALSO
--------
'mount(8)', 'tar(1)', 'lvcreate(8)', 'lvremove(8)', lvs(8)', 'umount(8)', 'rsync(1)'


AUTHOR
------
This program was initially written by Aleksey "Walrus" Kishkin from
MySQL AB, with suggestions from Peter Zaitsev and Lenz Grimmer.

It is currently maintained by Lenz Grimmer, <mailto:lenz@grimmer.com>[]


RESOURCES
---------
Main web site: http://www.lenzg.org/mylvmbackup/[]
Mailing list: http://www.freelists.org/list/mylvmbackup/[]
Source code, bug tracker: https://launchpad.net/mylvmbackup/[]


CREDITS
-------
Several people have contributed to the script since it has been released.
See the ChangeLog for more details.

Robin H. Johnson from the Gentoo project cleaned up the code and added
several useful features.

Fred Blaise contributed the initial support to use an external configuration
file and logging via syslog.

Eric Bergen provided the code that performs the InnoDB recovery prior
to performing the backup of LVM2 snapshot volumes. He also fixed the
broken handling of default options.

Kristian Köhntopp for suggesting the '--pidfile' option and suggesting to
add the output of the LVM statistics for being able to better tune the
snapshot size.

COPYING
-------
mylvmbackup is distributed under the GNU public license. See the file
COPYING for details.