The Goldfish

       --merge
              Merges a snapshot into its origin volume.  To check if your ker‐
              nel supports this feature, look for 'snapshot-merge' in the out‐
              put  of 'dmsetup targets'.  If both the origin and snapshot vol‐
              ume are not open the merge will start  immediately.   Otherwise,
              the  merge  will start the first time either the origin or snap‐
              shot are activated and both are closed.  Merging a snapshot into
              an  origin that cannot be closed, for example a root filesystem,
              is deferred until the next time the origin volume is  activated.
              When  merging starts, the resulting logical volume will have the
              origin's name, minor number and UUID.  While  the  merge  is  in
              progress,  reads  or  writes  to  the origin appear as they were
              directed to the snapshot being merged.  When the merge finishes,
              the merged snapshot is removed.  Multiple snapshots may be spec‐
              ified on the commandline or a @tag may be used to specify multi‐
              ple snapshots be merged to their respective origin.

[root@titanium ~]# lvcreate -L1G -n lv_test vg_titanium
  Logical volume "lv_test" created
[root@titanium ~]# mke2fs -j /dev/vg_titanium/lv_test 
mke2fs 1.41.14 (22-Dec-2010)
Filesystem label=
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
Stride=0 blocks, Stripe width=0 blocks
65536 inodes, 262144 blocks
13107 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=268435456
8 block groups
32768 blocks per group, 32768 fragments per group
8192 inodes per group
Superblock backups stored on blocks: 
	32768, 98304, 163840, 229376
 
Writing inode tables: done                            
Creating journal (8192 blocks): done
Writing superblocks and filesystem accounting information: done
 
This filesystem will be automatically checked every 33 mounts or
180 days, whichever comes first.  Use tune2fs -c or -i to override.
[root@titanium ~]# mkdir /mnt/test
[root@titanium ~]# mount /dev/vg_titanium/lv_test /mnt/test

[root@titanium ~]# touch /mnt/test/testdata-$(date +%Y%m%d%H%M%S)
[root@titanium ~]# ls -l /mnt/test/
total 20
drwx------. 2 root root 16384 Sep 19 00:39 lost+found
-rw-r--r--. 1 root root     0 Sep 19 00:39 testdata-20110919003936
[root@titanium ~]# SNAP_NAME="lv_test-snapshot-$(date +%Y%m%d%H%M%S)"
[root@titanium ~]# lvcreate -s /dev/vg_titanium/lv_test -L 1G -n $SNAP_NAME
  Logical volume "lv_test-snapshot-20110919003936" created
[root@titanium ~]# touch /mnt/test/testdata-$(date +%Y%m%d%H%M%S)
[root@titanium ~]# ls -l /mnt/test/
total 24
drwx------. 2 root root 16384 Sep 19 00:39 lost+found
-rw-r--r--. 1 root root     0 Sep 19 00:39 testdata-20110919003936
-rw-r--r--. 1 root root     0 Sep 19 00:39 testdata-20110919003937

[root@titanium ~]# lvconvert --merge /dev/vg_titanium/$SNAP_NAME
  Can't merge over open origin volume
  Merging of snapshot lv_test-snapshot-20110919003936 will start next activation.

[root@titanium ~]# umount /dev/vg_titanium/lv_test
[root@titanium ~]# lvchange -an /dev/vg_titanium/lv_test
[root@titanium ~]# lvchange -ay /dev/vg_titanium/lv_test
[root@titanium ~]# mount /dev/vg_titanium/lv_test /mnt/test
[root@titanium ~]# ls -l /mnt/test/
total 20
drwx------. 2 root root 16384 Sep 19 00:39 lost+found
-rw-r--r--. 1 root root     0 Sep 19 00:39 testdata-20110919003936

[root@titanium ~]# umount /dev/vg_titanium/lv_test
[root@titanium ~]# lvremove /dev/vg_titanium/lv_test
  Logical volume "lv_test-snapshot-20110919003936" successfully removed
Do you really want to remove active logical volume lv_test? [y/n]: y
  Logical volume "lv_test" successfully removed
rmdir /mnt/test

mysql> SHOW GLOBAL VARIABLES like 'general_log%'  ;
+------------------+-------------------------------+
| Variable_name    | Value                         |
+------------------+-------------------------------+
| general_log      | OFF                           |
| general_log_file | /var/lib/mysql/server2.log |
+------------------+-------------------------------+
2 rows in set (0.00 sec)
 
mysql> SET GLOBAL general_log = 'ON';
[root@server2 ~]# tail -f /var/lib/mysql/server2.log

mysql> STOP SLAVE;
mysql> RESET SLAVE;

mysql> RESET MASTER;
[root@server1 ~]# mysqldump -p  --all-databases --master-data > /var/lib/mysql/dbdump-`hostname -s`-`date +%Y%m%dT%H%M%S`.sql

rsync -a --progress /var/lib/mysql/dbdump-server1-20110616T153454.sql server2:/var/lib/mysql/

[root@server2 ~]#mysql -p  <  /var/lib/mysql/dbdump-server1-20110616T153454.sql
mysql> START SLAVE;
mysql> SHOW SLAVE STATUSG

mysql> RESET MASTER;
mysql> SHOW MASTER STATUS;
+------------------+----------+--------------+------------------+
| File             | Position | Binlog_Do_DB | Binlog_Ignore_DB |
+------------------+----------+--------------+------------------+
| mysql-bin.000001 |      106 |              |                  |
+------------------+----------+--------------+------------------+

mysql> CHANGE MASTER TO MASTER_LOG_FILE = 'mysql-bin.000001', MASTER_LOG_POS = 106;
mysql> SHOW SLAVE STATUS\G
mysql> START SLAVE;

mysql> SET GLOBAL general_log = 'ON';