How to migrate an existing MySQL 5.5 DB from latin1 to UTF-8.

Manual

Convert old latin1 DB to a new UTF8 one:

DBS="db1 db2"
for dbname in $DBS 
do
  mysqldump "${dbname}" > "${dbname}"latin1.sql
  cat "${dbname}"latin1.sql | sed "s#CHARSET=latin1#CHARSET=utf8#" | iconv -f iso8859-1 -t utf8 > "${dbname}"utf8.sql
done
====
Change in /etc/mysql/my.cnf:

[mysqld] 
init_connect='SET collation_connection = utf8_unicode_ci' 
init_connect='SET NAMES utf8' 
character-set-server=utf8 
collation-server=utf8_unicode_ci 
#skip-character-set-client-handshake

====
Then, restart DB with new settings in my.cnf:
/etc/init.d/mysql restart

Result is

mysql> show variables like "%character%";show variables like "%collation%";

+--------------------------+----------------------------+
| Variable_name            | Value                      |
+--------------------------+----------------------------+
| character_set_client     | utf8                       |
| character_set_connection | utf8                       |
| character_set_database   | utf8                       |
| character_set_filesystem | binary                     |
| character_set_results    | utf8                       |
| character_set_server     | utf8                       |
| character_set_system     | utf8                       |
| character_sets_dir       | /usr/share/mysql/charsets/ |
+--------------------------+----------------------------+
8 rows in set (0.00 sec)

+----------------------+-----------------+
| Variable_name        | Value           |
+----------------------+-----------------+
| collation_connection | utf8_unicode_ci |
| collation_database   | utf8_unicode_ci |
| collation_server     | utf8_unicode_ci |
+----------------------+-----------------+
3 rows in set (0.00 sec)

====
Then, recreate the DB in a new collation and charset:

for dbname in $DBS 
do
  echo "drop database ${dbname}; create database ${dbname}" | mysql
done

Then, put the prepared data back:

for dbname in $DBS 
do
  cat "${dbname}"utf8.sql | mysql "${dbname}"
done