Installing mylvmbackup on a RedHat Enterprise Linux or CentOS 5 system is simple and it is shown in this section:
Firstly, install perl-Config-IniFiles and perl-TimeDate:
Note
perl-Config-IniFiles is available only in the EPEL repository. This was covered earlier in this book in Chapter 3, MySQL Cluster Management; you can read the simple install guide for this repository at http://fedoraproject.org/wiki/EPEL/FAQ#How_can_I_install_the_packages_from_the_EPEL_software_repository.3F.
[root@node2 ~]# yum -y install perl-Config-IniFiles perl-TimeDate
Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile
* epel: www.mirrorservice.org
Installed: perl-Config-IniFiles.noarch 0:2.39-6.el5 perl-TimeDate.noarch 1:1.16-5.el5
Complete!Download mylvmbackup and extract the tar.gz file as follows:
[root@node2 ~]# cd /usr/src/
[root@node2 src]# wget http://lenzg.net/mylvmbackup/mylvmbackup-0.13.tar.gz
--18:16:11-- http://lenzg.net/mylvmbackup/mylvmbackup-0.13.tar.gz
Resolving lenzg.net... 213.83.63.50
Connecting to lenzg.net|213.83.63.50|:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: 37121 (36K) [application/x-tar]
Saving to: `mylvmbackup-0.13.tar.gz'
100%[=======================================================================================================>] 37,121 --.-K/s in 0.06s
18:16:11 (593 KB/s) - `mylvmbackup-0.13.tar.gz' saved [37121/37121]
[root@node2 src]# tar zxvf mylvmbackup-0.13.tar.gz
mylvmbackup-0.13/
mylvmbackup-0.13/ChangeLog
mylvmbackup-0.13/COPYING
mylvmbackup-0.13/CREDITS
mylvmbackup-0.13/hooks/
mylvmbackup-0.13/hooks/backupfailure.pm
mylvmbackup-0.13/hooks/logerr.pm
mylvmbackup-0.13/hooks/preflush.pm
mylvmbackup-0.13/INSTALL
mylvmbackup-0.13/Makefile
mylvmbackup-0.13/man/
mylvmbackup-0.13/man/mylvmbackup.pod
mylvmbackup-0.13/man/mylvmbackup.1
mylvmbackup-0.13/mylvmbackup
mylvmbackup-0.13/mylvmbackup.conf
mylvmbackup-0.13/mylvmbackup.pl.in
mylvmbackup-0.13/mylvmbackup.spec
mylvmbackup-0.13/mylvmbackup.spec.in
mylvmbackup-0.13/README
mylvmbackup-0.13/TODOChange to the new directory and install mylvmbackup as follows:
[root@node2 src]# cd mylvmbackup-0.13
[root@node2 mylvmbackup-0.13]# make install
test -d /usr/local/bin || /usr/bin/install -d /usr/local/bin
test -d /usr/local/man/man1 || /usr/bin/install -d /usr/local/man/man1
test -d /etc || /usr/bin/install -d /etc
test -d /usr/local/share/mylvmbackup || /usr/bin/install -d /usr/local/share/mylvmbackup
/usr/bin/install -m 755 mylvmbackup /usr/local/bin
/usr/bin/install -m 644 man/mylvmbackup.1 /usr/local/man/man1/mylvmbackup.1
if test -f /etc/mylvmbackup.conf ; then /bin/mv /etc/mylvmbackup.conf /etc/mylvmbackup.conf.bak ; fi
/usr/bin/install -m 600 mylvmbackup.conf /etc
for HOOK in hooks/backupfailure.pm hooks/logerr.pm hooks/preflush.pm ; do if [ ! -f /usr/local/share/mylvmbackup/$HOOK ] ; then /usr/bin/install -m 644 -v $HOOK /usr/local/share/mylvmbackup ; fi ; done
`hooks/backupfailure.pm' -> `/usr/local/share/mylvmbackup/backupfailure.pm'
`hooks/logerr.pm' -> `/usr/local/share/mylvmbackup/logerr.pm'
`hooks/preflush.pm' -> `/usr/local/share/mylvmbackup/preflush.pm'
mylvmbackup requires two things to work: the MySQL data directory must be on a logical volume and the volume group that contains this logical volume must have some spare space to hold the snapshot copy for writing. Check these with the following commands:
Firstly, run the vgs command to confirm that there is spare space available. In this case, there is 9.66G spare space in the volume group:
[root@node1 ~]# vgs
VG #PV #LV #SN Attr VSize VFree
system 1 3 0 wz--n- 29.41G 9.66GSecondly, check that there is a logical volume for MySQL with the lvs command and note the volume group (system in the following example):
[root@node1 ~]# lvs
LV VG Attr LSize Origin Snap% Move Log Copy% Convert
log system -wi-ao 1.94G
mysql system -wi-ao 10.00G
root system -wi-ao 7.81GFinally, check that the MySQL data directory is mounted on this logical volume:
[root@node1 ~]# df -h | grep mysql
/dev/mapper/system-mysql
9.9G 172M 9.2G 2% /var/lib/mysqlWith these things verified, you are ready to configure /etc/mylvmbackup.conf file.
Start with the self-explanatory [mysql] section that gives a user the privileges to lock tables.
In the [lvm] section, define the vgname and lvname from the output of vgs / lvs commands used earlier (in our example, the vgname is system and the lvname is mysql). The parameter lvsize determines how much space to keep for the snapshot—the volume group must have that much space free, and this is used to hold the data that is changed while the snapshot is open. The correct setting for this parameter depends on how busy your server is and how long backups take; you can start with 20 percent of the logical volume size.
An example configuration file is as follows:
# # mylvmbackup configuration file # [mysql] user=USER password=PASSWORD host=localhost port= socket= mycnf=/etc/my.cnf # # LVM-specific options # [lvm] vgname=dataVol lvname=mysql backuplv= # lvsize must be able to cope with differences lvsize=1G # # File system specific options # [fs] xfs=0 mountdir=/var/tmp/mylvmbackup/mnt/ backupdir=/var/tmp/mylvmbackup/backup/ relpath= # # Names of required external utilities # Make sure the $PATH is set accordingly, especially for cron jobs! # [tools] lvcreate=lvcreate lvremove=lvremove lvs=lvs mount=mount tar=tar compress=gzip rsync=rsync rsnap=rsnap umount=umount # # Other configuration options # [misc] backuptype=tar prefix=backup-ibactive suffix=_mysql tararg=cvf tarsuffixarg= tarfilesuffix=.tar.gz compressarg=--stdout --verbose --best rsyncarg=-avWP rsnaparg=7 datefmt=%Y%m%d_%H%M%S innodb_recover=0 pidfile=/var/tmp/mylvmbackup_recoverserver.pid skip_flush_tables=0 extra_flush_tables=0 skip_mycnf=0 hooksdir=/usr/share/mylvmbackup skip_hooks=0 keep_snapshot=0 keep_mount=0 quiet=0 # # Logging options. The Sys::Syslog module is required for syslog option # See "perldoc Sys::Syslog" for more information. # [logging] # 'console' (STDOUT, STDERR) or 'syslog' or 'both'. log_method=console # 'native', 'tcp', 'udp'. Default is 'native' syslog_socktype=native syslog_facility= # If using remote syslog, don't forget to change the socket type to tcp or udp. syslog_remotehost=
With the configuration file created, execute mylvmbackup to test your backup as follows:
[root@node1 ~]# mylvmbackup
20091206 18:39:24 Info: Connecting to database...
20091206 18:39:24 Info: Flushing tables with read lock...
20091206 18:39:24 Info: Taking position record into /tmp/mylvmbackup-backup-20091206_183924_mysql-mxAD4A.pos...
20091206 18:39:24 Info: Running: lvcreate -s --size=5G --name=mysql_snapshot /dev/system/mysql
File descriptor 4 (socket:[17769919]) leaked on lvcreate invocation. Parent PID 20180: /usr/bin/perl
Logical volume "mysql_snapshot" created
20091206 18:39:25 Info: DONE: taking LVM snapshot
20091206 18:39:25 Info: Unlocking tables...
20091206 18:39:25 Info: Disconnecting from database...
20091206 18:39:25 Info: Mounting snapshot...
20091206 18:39:25 Info: Running: lvremove -f /dev/system/mysql_snapshot
Logical volume "mysql_snapshot" successfully removed
20091206 18:39:26 Info: DONE: Removing snapshot
[root@node1 ~]# echo $?
0In this case, the tables were locked for less than a second.
Various parts of this procedure can fail for the following reasons:
The MySQL server can be down
The read lock cannot be successfully acquired
Insufficient spare space in the volume group to create the snapshot
The volume group or logical volume name does not exist (that is, a typo in the configuration file)
It is therefore essential in automated scripts to check the exit code ($?) and ensure that it is 0—and if it is not, you must schedule a manual look at the backup job.
If the script exits with an exit code of 0, the backup can be found in /var/tmp/mylvmbackup/backup/, which is ready for sending to a backup location. For example, you could scp or rsync it to an offsite location.