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MYLVMBACKUP

MYLVMBACKUP

Section: User Contributed Perl Documentation (1) Updated: 2010-02-02
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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 default 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. 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 rsnap, which is a wrapper around 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 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).  

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 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 --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.

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.

Hook scripts can also be implemented as Perl modules. The module must be named hookname.pm and must be a package of type hookname. The module must implement execute() which is called by mylvmbackup to initiate the hook. It must return boolean true/false (1 or 0) on success/failure. 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 run_hook() function. The module must also implement errmsg() which will return a string error message to be sent to log_msg(). This will be called by mylvmbackup when 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:

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
backupsuccess
after a successful backup
backupfailure
after a failed backup
logerr
when an error is logged
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. Note that hooks implemented as Perl modules (hookname.pm) have priority over ``plain'' hook scripts (hookname), if both exist, only the first one will be used. The execution of all hooks can be suppressed 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). A sample configuration file is included in the distribution.
--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. 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 host other than localhost overrides any given socket path value. The default is the empty string.
--port=number
Specifies the TCP port number to use for connecting to the MySQL server. This value is only honoured, if host is provided as well and is not equal to localhost. The default is the empty string.
--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.
--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.
--innodb_recover
Run InnoDB recovery on the writable snapshot 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/run/mysqld/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.
--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.
--keep_mount
If this option is given, mylvmbackup will not remove the mounted partition before terminating. This option also implies 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.
--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 /var/lib, but the MySQL data directory is /var/lib/mysql. In this case, relpath should be set to mysql. 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, rsync, rsnap and none.
--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.
--suffix=string
Suffix added to the backup file names (after the time stamp). The default value is _mysql.
--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/cache/mylvmbackup/mnt/. If the directory does not exist, it will be created.

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

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

Instead of a local directory, you can also provide a valid rsync URL here, e.g. username@hostname:/path, hostname:path or 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 /var/cache/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 cvf.
--tarsuffixarg=string
Specifies the suffix arguments for the tar program. The default is the empty string. To exclude a database, you would pass --exclude dbname here.
--tarfilesuffix=string
Specifies the suffix for the tarball. The default is .tar.gz.
--compress=string
Specifies the name of the compression program. Only used if backuptype is set to tar. Some possibilities are gzip, bzip2 or lzma. The program must support reading the to be compressed data from stdin and writing to stdout, without requiring intermediate temporary files (for this reason, 7zip cannot be used). It's also possible to use cat. In this case, no compression will be done. Make sure to update the compressarg option accordingly. The default is gzip. Can be left empty.
--compressarg=string
Specifies the command line options given to the compress program. For gzip, that would be --stdout --verbose --best, for lzma or bzip2 --stdout --verbose -7 and for cat, it would be empty. The default is --stdout --verbose --best.
--rsnap=string
Specifies the pathname for the rsnap program. The default is rsnap.
--rsnaparg=string
Specifies the arguments for the rsnap program. The default is 7, which causes it to keep the last 7 snapshot (useful when running mylvmbackup once per day).
--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. 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, rsync or rsnap may be required instead of tar and gzip, depending on which backup type you choose.  

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, <lenz@grimmer.com>  

RESOURCES

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

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

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

CREDITS

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

COPYING

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


 

Index

NAME
SYNOPSIS
DESCRIPTION
GENERAL HINTS
HOOKS
OPTIONS
FILES
REQUIREMENTS
SEE ALSO
AUTHOR
RESOURCES
CREDITS
COPYING

This document was created by man2html, using the manual pages.
Time: 21:24:09 GMT, April 16, 2011