背景概述
由于安装数据库时将mysql的数据目录放在了根目录下，现在存储空间不足，想通过mv将数据目录移动到其他目录下，但将数据目录移动到其他数据目录后，启动数据库失败。
问题复现
本次测试基于 MySQL 8.0.31
1.关闭数据库
mysql> shutdown; Query OK, 0 rows affected (0.02 sec)
2.查看当前数据目录所在位置
shell> pwd /mysql80
3.通过mv移动整个MySQL数据目录到其他目录
shell> mv /mysql80 /data shell> cd /data/mysql80/svr shell> ln -s mysql-8.0.31-linux-glibc2.12-x86_64 mysql
4.修改属主属组
shell> chown -R mysql.mysql /data
5.修改配置文件中数据目录的地址
shell> sed -i 's#/mysql80#/data/mysql80#g' my5001.cnf
6.启动数据库
shell> /data/mysql80/svr/mysql/bin/mysqld_safe \ --defaults-file=/data/mysql80/conf/my5001.cnf --user=mysql &
此时启动数据库失败，错误日志报错如下：
mysqld: File '/mysql80/dbdata/data5001/log/binlog.000012' not found (OS errno 2 - No such file or directory)2023-02-27T10:38:09.240576+08:00 0 [ERROR] [MY-010958] [Server] Could not open log file.2023-02-27T10:38:09.240657+08:00 0 [ERROR] [MY-010041] [Server] Can't init tc log2023-02-27T10:38:09.240718+08:00 0 [ERROR] [MY-010119] [Server] Aborting2023-02-27T10:38:10.548605+08:00 0 [System] [MY-010910] [Server] /data/mysql80/svr/mysql/bin/mysqld: Shutdown complete (mysqld 8.0.31) MySQL Community Server - GPL.
这里报错显示找不到binlog文件，并且报错显示的binlog的目录还是之前的，但是配置文件中的目录已经修改
shell> grep 'log-bin' my5001.cnf log-bin=/data/mysql80/dbdata/data5001/log/binlog log-bin-trust-function-creators
7.问题解决
最后通过查找发现 binlog.index 文件中存放着每个binlog文件的绝对路径地址，这里的路径还是之前路径，内容如下：
shell> cat binlog.index /mysql80/dbdata/data5001/log/binlog.000001 /mysql80/dbdata/data5001/log/binlog.000002 /mysql80/dbdata/data5001/log/binlog.000003 /mysql80/dbdata/data5001/log/binlog.000004 /mysql80/dbdata/data5001/log/binlog.000005 /mysql80/dbdata/data5001/log/binlog.000006 /mysql80/dbdata/data5001/log/binlog.000007 /mysql80/dbdata/data5001/log/binlog.000008 /mysql80/dbdata/data5001/log/binlog.000009 /mysql80/dbdata/data5001/log/binlog.000010 /mysql80/dbdata/data5001/log/binlog.000011 /mysql80/dbdata/data5001/log/binlog.000012
修改binlog.index文件中binlog的绝对路径：
shell> sed -i 's#/mysql80#/data/mysql80#g' binlog.index shell> cat binlog.index /data/mysql80/dbdata/data5001/log/binlog.000001 /data/mysql80/dbdata/data5001/log/binlog.000002 /data/mysql80/dbdata/data5001/log/binlog.000003 /data/mysql80/dbdata/data5001/log/binlog.000004 /data/mysql80/dbdata/data5001/log/binlog.000005 /data/mysql80/dbdata/data5001/log/binlog.000006 /data/mysql80/dbdata/data5001/log/binlog.000007 /data/mysql80/dbdata/data5001/log/binlog.000008 /data/mysql80/dbdata/data5001/log/binlog.000009 /data/mysql80/dbdata/data5001/log/binlog.000010 /data/mysql80/dbdata/data5001/log/binlog.000011 /data/mysql80/dbdata/data5001/log/binlog.000012
8.启动数据库
shell> /data/mysql80/svr/mysql/bin/mysqld_safe --defaults-file=/data/mysql80/conf/my5001.cnf --user=mysql &
数据库启动成功。
9.作为从节点
需要注意的是，如果该实例还作为其他实例的从节点，还需要设置 relaylog.index 文件中relay log的绝对路径，否则会报如下错误： 错误日志报错：
2023-02-27T15:56:55.224372+08:00 0 [ERROR] [MY-010599] [Repl] log /mysql80/dbdata/data5002/log/relaylog.000002 listed in the index, but failed to stat.
2023-02-27T15:56:55.224422+08:00 0 [ERROR] [MY-011059] [Repl] Error counting relay log space.
2023-02-27T15:56:55.226571+08:00 0 [ERROR] [MY-010426] [Repl] Slave: Failed to initialize the master info structure for channel ''; its record may still be present in 'mysql.slave_master_info' table, consider deleting it.
2023-02-27T15:56:55.226622+08:00 0 [ERROR] [MY-010529] [Repl] Failed to create or recover replication info repositories.
执行 start replica 时也会报错：
# 客户端报错
mysql> start replica;
ERROR 1872 (HY000): Slave failed to initialize relay log info structure from the repository
# error log报错
2023-02-27T15:57:53.858798+08:00 8 [ERROR] [MY-013124124] [Repl] Slave SQL for channel '': Slave failed to initialize relay log info structure from the repository, Error_code: MY-013124124
10.问题解决
修改 relaylog.index 文件中relay log的绝对路径
sed -i 's#/mysql80#/data/mysql80#g' relaylog.index
重新启动数据库，并启动主从复制
# 重启实例 mysql> restart; # 启动主从复制 mysql> start replica;
此时主从复制恢复正常。
