=head1 NAME

mylvmbackup - a utility for creating MySQL backups using LVM snapshots

=head1 SYNOPSIS

mylvmbackup [OPTIONS]

=head1 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 I<tar> program. By default, the archive file is created using a name
of the form I<backup-YYYYMMDD_hhmmss_mysql.tar.gz>, where I<YYYY>, I<MM>, I<DD>,
I<hh>, I<mm>, and I<ss> represent the year, month, day, hour, minute, and second
of the time at which the backup occurred. The default prefix I<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 I<tar>, you may use I<rsync>. This process is nearly
identical, with the exception that the file suffix is not used. The rsync
backup can perform both local backups as well as backing up to a remote 
server using rsyncd or rsync via SSH.

mylvmbackup also supports creating backups by using I<rsnap>, which is a
wrapper around I<rsync> to automatically maintain and rotate a given number of
last backups (7 by default). It utilizes hard links to link to unchanged files
for saving disk space.

Additionally, a backup type I<none> is provided for cases where the user wants
to use mylvmbackup only for creating the snapshots and intends to perform the
actual backup by using the appropriate hooks. (Or for cases where the snapshot
itself is considered to be the backup).

=head1 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 I<--host> or I<--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 I<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 log 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 I<--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 I<--innodb-file-per-table>, I<--innodb-data-home-dir>,
I<--innodb-data-file-path> or I<--innodb-log-group-home-dir> that modify the
default file layout for InnoDB tables.

If you use InnoDB tables exclusively, you may also want to consider to include
the option I<--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!

=head1 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 I<hooksdir> configuration option points to
(I</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.

Hook scripts can also be implemented as Perl modules. The module must be named
I<hookname.pm> and must be a package of type I<hookname>. The module must
implement I<execute()> which is called by mylvmbackup to initiate the hook. It
must return boolean true/false (1 or 0) on success/failure. I<execute()> will
be passed 2 parameters. The first parameter is a clone() of the global database
handle $dbh. This will allow hook scripts to interact with the database using
the established connection.  The second parameter is a string containing any
messages passed to the I<run_hook()> function.  The module must also implement
I<errmsg()> which will return a string error message to be sent to
I<log_msg()>. This will be called by I<mylvmbackup> when I<execute()> returns
false/0.

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

=over 4

=item B<preconnect>

before a connection to the database server is established

=item B<preflush>

before calling FLUSH TABLES

=item B<presnapshot>

before the file system snapshot is created

=item B<preunlock>

before the database tables are unlocked again

=item B<predisconnect>

before the connection to the database server is released

=item B<premount>

before the snapshot volume is mounted

=item B<prebackup>

before the snapshot backup will be performed

=item B<backupsuccess>

after a successful backup

=item B<backupfailure>

after a failed backup

=item B<logerr>

when an error is logged

=item B<precleanup>

before the snapshot is unmounted and discarded

=back

These hooks are optional and will only be called if a file for the particular
stage exists and is executable. Note that hooks implemented as Perl modules
(I<hookname.pm>) have priority over "plain" hook scripts (I<hookname>), if both
exist, only the first one will be used. The execution of all hooks can be
suppressed by passing the I<--skip_hooks> option or by setting the
I<skip_hooks> configuration option to I<1>;

=head1 OPTIONS

mylvmbackup supports the following command line options. The same options can
also be defined in the I</etc/mylvmbackup.conf> configuration file (omitting
the leading dashes, of course). A sample configuration file is included in
the distribution.

=over 4

=item B<--user=string>

Specifies the username to use for connecting to the MySQL server.
The default is I<root>.

=item B<--password=string>

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

=item B<--host=string>

Specifies the host name to use for connecting to the MySQL server. Note that
mylvmbackup needs to be run on the same system that the MySQL server to be
backed up runs on - do not enter a remote host's host name or IP address here!
A non-empty value for I<host> other than I<localhost> overrides any given
I<socket> path value.
The default is the empty string.

=item B<--port=number>

Specifies the TCP port number to use for connecting to the MySQL server.
This value is only honoured, if I<host> is provided as well and is not
equal to I<localhost>.
The default is the empty string.

=item B<--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.

=item B<--quiet>

Suppresses logging of informal messages. Warnings and errors will still
be printed or logged (depending on the selected logging mechanism).
The default is verbose logging.

=item B<--innodb_recover>

Run InnoDB recovery on the writable snapshot prior to performing the backup.

=item B<--skip_flush_tables>

Don't issue a I<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.

=item B<--extra_flush_tables>

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

=item B<--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
I<--innodb_recover>). Must be different from the PID file that the actual
running server uses.
The default is I</var/tmp/mylvmbackup_recoverserver.pid>

=item B<--lvcreate=string>

Specifies the pathname for the I<lvcreate> program.
The default is I<lvcreate>.

=item B<--lvremove=string>

Specifies the pathname for the I<lvremove> program.
The default is I<lvremove>.

=item B<--lvs=string>

Specifies the pathname for the I<lvs> program.
The default is I<lvs>.

=item B<--mysqld_safe=string>

Specifies the pathname for the I<mysqld_safe> program.
The default is I<mysqld_safe>. 
Only used to perform InnoDB recovery.

=item B<--mycnf=string>

Specifies the name of the MySQL config file to include in the backup.
The default is I</etc/my.cnf>.

=item B<--skip_mycnf>

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

=item B<--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 I</usr/share/mylvmbackup>.

=item B<--skip_hooks>

Skip invoking any external hooks during the backup.

=item B<--vgname=string>

Specifies the volume group of the logical volume where the MySQL
data directory is located.
The default is I<mysql>.

=item B<--lvname=string>

Specifies the name of the logical volume where the MySQL data
directory is located.
The default is I<data>.

=item B<--backuplv=string>

Specifies the name of the logical volume for the snapshot volume.
The default is appending B<_snapshot> to the lvname.

=item B<--keep_snapshot>

If this option is given, mylvmbackup will not remove the snapshot
before terminating. Note that keeping multiple LVM snapshots open at
the same time can reduce I/O performance and you will need to manually
discard the snapshot before invoking mylvmbackup again.

=item B<--keep_mount>

If this option is given, mylvmbackup will not remove the mounted partition
before terminating. This option also implies I<keep_snapshot=1>, as it would
not be useful if the snapshot is removed. You need to manually unmount this
directory before invoking mylvmbackup again.

=item B<--relpath=string>

Relative path on the logical volume to the MySQL data directory (no leading or
trailing slash). Example: the logical volume is mounted on I</var/lib>, but the
MySQL data directory is /var/lib/mysql. In this case, I<relpath> should be set
to I<mysql>.
The default is the empty string.

=item B<--lvsize=string>

Specifies the size for the snapshot volume.
The default is I<5G> (5 gigabytes).

=item B<--backuptype=string>

Specifies what type of backup to perform. The available options are
I<tar>, I<rsync>, I<rsnap> and I<none>.

=item B<--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 I<backup>.

=item B<--suffix=string>

Suffix added to the backup file names (after the time stamp).
The default value is I<_mysql>.

=item B<--datefmt=string>

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

=item B<--mountdir=string>

Path for mounting the snapshot volume to.
The default value is I</var/tmp/mylvmbackup/mnt/>.
If the directory does not exist, it will be created.

It is possible to use selected I<timestr()> formatting sequences to create
directory names which contain a dynamic date value. Currently, the following
format strings are supported:
I<%Y> 4-digit year (e.g. 2009),
I<%m> month (01..12),
I<%d> day of month, leading zero
I<%h> month abbreviation, 
I<%H> hour, 24 hour clock, leading zero
I<%M> minute, leading zero
I<%S> seconds, leading zero
Example: I<$mountdir=/path/to/%Y-%m-%d> will expand to I</path/to/2009-06-13>

=item B<--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. If the directory does not exist, it will be created.

It is possible to use selected I<timestr()> formatting sequences to create
directory names which contain a dynamic date value. Currently, the following
format strings are supported:
I<%Y> 4-digit year (e.g. 2009),
I<%m> month (01..12),
I<%d> day of month, leading zero
I<%h> month abbreviation, 
I<%H> hour, 24 hour clock, leading zero
I<%M> minute, leading zero
I<%S> seconds, leading zero
Example: I<$mountdir=/path/to/%Y-%m-%d> will expand to I</path/to/2009-06-13>

Instead of a local directory, you can also provide a valid rsync URL here, e.g.
I<username@hostname:/path>, I<hostname:path> or I<hostname::rsync-module/path>.
This requires a properly configured remote rsync setup (e.g. pre-setup SSH keys
or a working rsyncd configuration).

The default is I</var/tmp/mylvmbackup/backup/>

=item B<--mount=string>

Specifies the pathname for the I<mount> program.
The default is I<mount>.

=item B<--umount=string>

Specifies the pathname for the I<umount> program.
The default is I<umount>.

=item B<--tar=string>

Specifies the pathname for the I<tar> program.
The default is I<tar>.

=item B<--tararg=string>

Specifies the initial arguments for the I<tar> program.
The default is I<cvf>.

=item B<--tarsuffixarg=string>

Specifies the suffix arguments for the I<tar> program.
The default is the empty string.
To exclude a database, you would pass I<--exclude dbname> here.

=item B<--tarfilesuffix=string>

Specifies the suffix for the tarball.
The default is I<.tar.gz>.

=item B<--compress=string>

Specifies the name of the compression program. Only used if I<backuptype> is
set to I<tar>. Some possibilities are I<gzip>, I<bzip2> or I<lzma>.
The program must support reading the to be compressed data from I<stdin> and
writing to I<stdout>, without requiring intermediate temporary files (for this
reason, 7zip cannot be used). It's also possible to use I<cat>. In this case,
no compression will be done. Make sure to update the I<compressarg> option
accordingly.
The default is I<gzip>. Can be left empty.

=item B<--compressarg=string>

Specifies the command line options given to the I<compress> program. For I<gzip>,
that would be I<--stdout --verbose --best>, for I<lzma> or I<bzip2> I<--stdout --verbose -7>
and for I<cat>, it would be empty.
The default is I<--stdout --verbose --best>.

=item B<--rsnap=string>

Specifies the pathname for the I<rsnap> program.
The default is I<rsnap>.

=item B<--rsnaparg=string>

Specifies the arguments for the I<rsnap> program.
The default is I<7>, which causes it to keep the last 7 snapshot (useful
when running I<mylvmbackup> once per day).

=item B<--rsync=string>

Specifies the pathname for the I<rsync> program.
The default is I<rsync>.

=item B<--rsyncarg=string>

Specifies the arguments for the I<rsync> program.
The default is I<-avWP>. Should must ensure that the recursive option is
included either implicitly by I<-a>, or explicitly.

=item B<--xfs>

Use the I<nouuid> mount option to safely mount snapshot partitions that
use the XFS file system.

=item B<--log_method=string>

How to log output from this script. Valid options are I<console>, I<syslog>
or I<both>.
The default value is I<console>.

=item B<--syslog_socktype=string>

What type of socket to use for connecting to the syslog service. Valid
options are I<native>, I<tcp> and I<udp>.
The default value is I<native>.

=item B<--syslog_facility=string>

Define a particular syslog facility
Default value is the empty string.

=item B<--syslog_remotehost=string>

Host name of a remote syslog server.

=item B<--configfile=string>

Specify an alternative configuration file.
The default is I</etc/mylvmbackup.conf>.

=item B<--help>

Displays a help message showing the available options.

=back

=head1 FILES

=over 4

=item B</etc/mylvbackup.conf>

The I<mylvmbackup> configuration file

=item B<mylvmbackup>

The executable Perl script that performs the work.

=back

=head1 REQUIREMENTS

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

It also requires several other external programs: GNU I<tar> and I<gzip> to back
up the data, LVM utilities (I<lvcreate>, I<lvremove> and I<lvs>) to create and
remove the LVM snapshot, and the system utilities I<mount> and I<umount>.
Please note that mylvmbackup requires Linux LVM Version 2 or higher. It does not
work on LVMv1, as this version does not support writable snapshots.

Optionally, I<rsync> or I<rsnap> may be required instead of I<tar> and I<gzip>,
depending on which backup type you choose.

=head1 SEE ALSO

mount(8), tar(1), lvcreate(8), lvremove(8), lvs(8), umount(8), rsync(1)

=head1 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, <lenz@grimmer.com>

=head1 RESOURCES

Main web site: http://www.lenzg.net/mylvmbackup

Mailing list: https://launchpad.net/~mylvmbackup-discuss

Source code, bug tracker: https://launchpad.net/mylvmbackup

=head1 CREDITS

See the file CREDITS included in the distribution for a list of individual
contributors.

=head1 COPYING

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