文本只是新手级别（临时遇上，硬着头皮上的这种，从 RDS 同步到本地mysql的教程很少，而且有些情况还不太一样，来来回来折腾了一周才出了结果），很多my.cnf 里的参数都不知所以，所以基本上都是照搬 RDS 里面的参数，一句一句的查，然后写到本地的 my.cnf 里面，希望我的经验能帮到有需要的各位。
备份恢复到本地的相关说明，请参考https://help.aliyun.com/knowledge_detail/41817.html
本例环境为 Mysql5.6
阿里云 RDS / Mysql 5.6
本地环境Ubuntu 14.04 / Mysql 5.6
1.安装Percona Xtrabackup
dpkg -i percona-release_0.1-5.$(lsb_release -sc)_all.deb
apt-get update
apt-get install percona-xtrabackup-24
2.安装Mysql服务和客户端
apt-get install mysql-server-5.6 mysql-client-5.6
/etc/init.d/mysql stop
3.下载数据库备份文件
wget -c '<数据备份文件外网下载地址>' -O <自定义文件名>.tar.gz
4.解压备份文件
bash rds_backup_extract.sh -f <数据备份文件名>.tar.gz -C /home/mysql/data
5.恢复解压好的文件
innobackupex --defaults-file=/home/mysql/data/backup-my.cnf --apply-log /home/mysql/data
6.修改backup-my.cnf参数
vim /home/mysql/data/backup-my.cnf
# This MySQL options file was generated by >>innobackupex.
# The MySQL server
# 以下参数请勿直接复制，注释的5个参数是固定的，不然启动会报错
[mysqld]
innodb_checksum_algorithm=innodb
#innodb_log_checksum_algorithm=innodb
innodb_data_file_path=ibdata1:200M:autoextend
innodb_log_files_in_group=2
innodb_log_file_size=1048576000
#innodb_fast_checksum=false
innodb_page_size=16384
#innodb_log_block_size=512
innodb_undo_directory=.
innodb_undo_tablespaces=0
#rds_encrypt_data=false
#innodb_encrypt_algorithm=aes_128_ecb
7.修改文件属主
chown -R mysql:mysql /home/mysql/data
8.启动MySQL进程
mysqld_safe --defaults-file=/home/mysql/data/backup-my.cnf --user=mysql --datadir=/home/mysql/data
9.登录MySQL数据库进行修改
注：删除表示因为无法设置 slave ，需要重新导入（mysql 自带）
mysql -urootmysql>delete from mysql.db where user<>'root' and char_length(user)>0;delete from mysql.tables_priv where user<>'root' and char_length(user)>0;flush privileges;
mysql>use mysql;
mysql>drop table slave_master_info;
mysql>drop table slave_relay_log_info;
mysql>drop table slave_worker_info;
mysql>drop table innodb_index_stats;
mysql>drop table innodb_table_stats;
mysql>source /usr/share/mysql/mysql_system_tables.sql
mysql>quit
10.修改my.cnf（把backup-my.cnf参数复制到my.cnf）
mysqladmin shutdown
vim /etc/mysql/my.cnf[client]
port = 3306
socket = /var/run/mysqld/mysqld.sock
[mysqld_safe]
socket = /var/run/mysqld/mysqld.sock
nice = 0[mysqld]
user = mysql
pid-file = /var/run/mysqld/mysqld.pid
socket = /var/run/mysqld/mysqld.sock
port = 3306
basedir = /usr
datadir = /home/mysql/data
tmpdir = /tmp
lc-messages-dir = /usr/share/mysql
skip-external-locking
myisam-recover = BACKUP
log_error = /var/log/mysql/error.log
#阿里云RDS优化配置
auto_increment_increment = 1
auto_increment_offset = 1
back_log = 3000
binlog_cache_size = 1M
binlog_checksum = CRC32
binlog_row_image = full
binlog_stmt_cache_size = 32768
character_set_server = utf8
concurrent_insert = 1
connect_timeout = 10
default_storage_engine = InnoDB
default_time_zone = SYSTEM
default_week_format = 0
delayed_insert_limit = 100
delayed_insert_timeout = 300
delayed_queue_size = 1000
delay_key_write = ON
div_precision_increment = 4
eq_range_index_dive_limit = 10
explicit_defaults_for_timestamp = false
ft_min_word_len = 4
ft_query_expansion_limit = 20
group_concat_max_len = 1024
innodb_adaptive_hash_index = ON
innodb_additional_mem_pool_size = 2097152
innodb_autoinc_lock_mode = 1
innodb_concurrency_tickets = 500
innodb_ft_max_token_size = 84
innodb_ft_min_token_size = 3
innodb_large_prefix = 0
innodb_lock_wait_timeout = 50
innodb_max_dirty_pages_pct = 75
innodb_old_blocks_pct = 37
innodb_old_blocks_time = 0
innodb_online_alter_log_max_size = 134217728
innodb_open_files = 300
innodb_print_all_deadlocks = OFF
innodb_purge_batch_size = 20
innodb_purge_threads = 1
innodb_read_ahead_threshold = 56
innodb_read_io_threads = 4
innodb_rollback_on_timeout = OFF
innodb_stats_method = nulls_equal
innodb_stats_on_metadata = OFF
innodb_stats_sample_pages = 8
innodb_strict_mode = OFF
innodb_table_locks = ON
innodb_thread_concurrency = 0
innodb_thread_sleep_delay = 10000
innodb_write_io_threads = 4
interactive_timeout = 7200
key_cache_age_threshold = 300
key_cache_block_size = 1024
key_cache_division_limit = 100
log_queries_not_using_indexes = OFF
long_query_time = 1
#loose_max_statement_time = 0
#loose_rds_indexstat = OFF
#loose_rds_max_tmp_disk_space = 10737418240
#loose_rds_tablestat = ON
#loose_rds_threads_running_high_watermark = 50000
#loose_tokudb_buffer_pool_ratio = 0
lower_case_table_names = 1
low_priority_updates = 0
max_allowed_packet = 1024M
max_connect_errors = 20
max_length_for_sort_data = 1024
max_prepared_stmt_count = 16382
max_write_lock_count = 102400
myisam_sort_buffer_size = 262144
net_read_timeout = 30
net_retry_count = 10
net_write_timeout = 60
open_files_limit = 65535
performance_schema = OFF
query_alloc_block_size = 8192
query_cache_limit = 1048576
query_cache_size = 0
query_cache_type = 1
query_cache_wlock_invalidate = OFF
query_prealloc_size = 8192
#rds_reset_all_filter = 0
slow_launch_time = 2
sql_mode =
table_definition_cache = 512
table_open_cache = 2000
thread_stack = 262144
tmp_table_size = 262144
transaction_isolation = READ-COMMITTED
wait_timeout = 86400
#优化结束
#GTID设置
server-id = 148
log-bin = mysql.bin
log-bin-index = mysql-bin.index
log-slave-updates = 1
skip_slave_start = 1
relay-log = relay-log
relay_log_index = relay-log.index
expire_logs_days = 0
max_binlog_size = 500M
default-storage-engine=INNODB
master-info-repository=TABLE
relay-log-info_repository=TABLE
binlog-format=ROW
gtid-mode=on
enforce-gtid-consistency=true
#backup-my.cnf参数
innodb_checksum_algorithm=innodb
#innodb_log_checksum_algorithm=innodb
innodb_data_file_path=ibdata1:200M:autoextend
innodb_log_files_in_group=2
innodb_log_file_size=1048576000
#innodb_fast_checksum=false
innodb_page_size=16384
#innodb_log_block_size=512
innodb_undo_directory=.
innodb_undo_tablespaces=0
#backup-my.cnf结束
replicate-ignore-db=mysql
replicate-ignore-db=test
replicate-ignore-db=information_schema
replicate-ignore-db=performance_schema
replicate-do-db=db1
replicate-do-db=db2
#GTID结束
[mysqldump]
quick
quote-names
max_allowed_packet = 16M[mysql]
[isamchk]
key_buffer = 16M
!includedir /etc/mysql/conf.d/
注：my.cnf的参数可以参考RDS的参数，我这里是照搬，请自己对照情况进行修改。
11.设置slave(请先在rds控制台创建一个用来同步的账户，建议只读)
/etc/init.d/mysql/restart
cat /home/data/mysql/xtrabackup_slave_info
#文件里面就两段字，复制下来，待会在 mysql 里面写入。
mysql -urootmysql>SET GLOBAL gtid_purged='xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx:1-123456';
mysql>CHANGE MASTER TO MASTER_HOST='RDS外网地址', MASTER_PORT=3306, MASTER_USER='同步账号', MASTER_PASSWORD='同步密码', MASTER_AUTO_POSITION=1;
mysql>START SLAVE;
mysql>SHOW SLAVE STATUS \G
问题解答
1.首次启动数据库出现如下提示
[ERROR] InnoDB: ./ibdata1 can't be opened in read-write mode
[ERROR] InnoDB: The system tablespace must be writable!
[ERROR] Plugin 'InnoDB' init function returned error.
[ERROR] Plugin 'InnoDB' registration as a STORAGE ENGINE failed.
[ERROR] Unknown/unsupported storage engine: InnoDB
[ERROR] AbortingPS：重启服务器即可，删除ib*什么的不管用。
2.unknown variable 'xxxx'
[ERROR]/usr/sbin/mysqld: unknown variable 'xxxx'
PS:到my.cnf里面注释xxxx
3.Table './mysql/xxx' 报错
[ERROR] /usr/sbin/mysqld: Table './mysql/db' is marked as crashed and should be repaired
[Warning] Checking table: './mysql/db'
[ERROR] 1 client is using or hasn't closed the table properly
[ERROR] /usr/sbin/mysqld: Table './mysql/event' is marked as crashed and should be repaired
[Warning] Checking table: './mysql/event'
[ERROR] 1 client is using or hasn't closed the table properlyPS：使用myisamchk -c -r /home/mysql/data/db/tablesname.MYI修复即可
4.information that should help you find out what is causing the crash.
It is possible that mysqld could use up to
key_buffer_size + (read_buffer_size + sort_buffer_size)*max_threads = 68104 K bytes of memory
Hope that's ok; if not, decrease some variables in the equation.
Thread pointer: 0xxxxxxxxxxxxx
Attempting backtrace. You can use the following information to find out
where mysqld died. If you see no messages after this, something went
terribly wrong...
PS：...他只是卡住了而已，my.cnf里面部分参数设置不当，等一会就可以连了。。别问我为什么知道。。
5.同步时报1236错误
[ERROR] Error reading packet from server: The slave is connecting using CHANGE MASTER TO MASTER_AUTO_POSITION = 1, but the master has purged binary logs containing GTIDs that the slave requires. (server_errno=1236)
ERROR] Slave I/O: Got fatal error 1236 from master when reading data from binary log: 'The slave is connecting using CHANGE MASTER TO MASTER_AUTO_POSITION = 1, but the master has purged binary logs containing GTIDs that the slave requires.', Error_code: 1236
[ERROR] Error reading packet from server: The slave is connecting using CHANGE MASTER TO MASTER_AUTO_POSITION = 1, but the master has purged binary logs containing GTIDs that the slave requires. (server_errno=1236)PS:重新从RDS获取新的备份（当前的新备份）
最后，本地my.cnf里面的配置，如果你不知道有些参数数值应该设置多少，可以登陆RDS服务器使用show命令进行查询，查询到的数值单位是字节，不会换算自己百度用工具换算一下就行，上文中关于my.cnf阿里云优化的部分，全部使用了RDS控制台里面的参数（导出复制进去就行，记得注释掉有rds的参数），RDS里面没有的参数，你本地可以直接注释掉。
对于GTID的参数，除了 server-id 不能与 master 一样，其他的都可以从 RDS 里面查询。
以上，遇到问题欢迎留言。
