首先将MySQL安全的关闭。
/etc/init.d/mysqld stop [root@elk-node03 bin]# mysql Welcome to the MySQL monitor. Commands end with ; or \g. Your MySQL connection id is 1 Server version: 5.6.36-log MySQL Community Server (GPL) Copyright (c) 2000, 2017, Oracle and/or its affiliates. All rights reserved. Oracle is a registered trademark of Oracle Corporation and/or its affiliates. Other names may be trademarks of their respective owners. Type 'help;' or '\h' for help. Type '\c' to clear the current input statement. (root@localhost:mysql.sock)[(none)]>然后将mysql的软链接切换到5.7的版本上面
# 切换之前 [root@elk-node03 application]# ls -ld mysql* lrwxrwxrwx. 1 root root 48 Feb 14 20:10 mysql -> /application/mysql-5.6.36-linux-glibc2.5-x86_64/ drwxr-xr-x. 13 root root 4096 Feb 17 21:10 mysql-5.6.36-linux-glibc2.5-x86_64 drwxr-xr-x. 10 mysql mysql 4096 Feb 17 20:15 mysql-5.7.20-linux-glibc2.12-x86_64 # 切换之后 [root@elk-node03 application]# unlink mysql [root@elk-node03 application]# ln -s /application/mysql-5.7.20-linux-glibc2.12-x86_64/ /application/mysql [root@elk-node03 application]# ls -ld mysql* lrwxrwxrwx. 1 root root 49 Feb 18 07:36 mysql -> /application/mysql-5.7.20-linux-glibc2.12-x86_64/ drwxr-xr-x. 13 root root 4096 Feb 17 21:10 mysql-5.6.36-linux-glibc2.5-x86_64 drwxr-xr-x. 10 mysql mysql 4096 Feb 17 20:15 mysql-5.7.20-linux-glibc2.12-x86_64这个时候如果启动mysql的话是可以看到：
[root@elk-node03 application]# /etc/init.d/mysqld start Starting MySQL.................... SUCCESS! [root@elk-node03 application]# mysql Welcome to the MySQL monitor. Commands end with ; or \g. Your MySQL connection id is 3 Server version: 5.7.20-log MySQL Community Server (GPL) Copyright (c) 2000, 2017, Oracle and/or its affiliates. All rights reserved. Oracle is a registered trademark of Oracle Corporation and/or its affiliates. Other names may be trademarks of their respective owners. Type 'help;' or '\h' for help. Type '\c' to clear the current input statement. (root@localhost:mysql.sock)[(none)]>show databases; +--------------------+ | Database | +--------------------+ | information_schema | | mysql | | performance_schema | | test | +--------------------+ 4 rows in set (0.00 sec)可以看到已经升级到了5.7版本，只是看起来升级成功了。如果查看error.log日志，那么就会发现有许多的报错。这个时候还需要使用另一个命令来修复。
[root@elk-node03 application]# mysql_upgrade -uroot -p Enter password: Checking if update is needed. Checking server version. Running queries to upgrade MySQL server. Checking system database. mysql.columns_priv OK mysql.db OK mysql.engine_cost OK mysql.event OK mysql.func OK mysql.general_log OK mysql.gtid_executed OK mysql.help_category OK mysql.help_keyword OK mysql.help_relation OK mysql.help_topic OK mysql.innodb_index_stats OK mysql.innodb_table_stats OK mysql.ndb_binlog_index OK mysql.plugin OK mysql.proc OK mysql.procs_priv OK mysql.proxies_priv OK mysql.server_cost OK mysql.servers OK mysql.slave_master_info OK mysql.slave_relay_log_info OK mysql.slave_worker_info OK mysql.slow_log OK mysql.tables_priv OK mysql.time_zone OK mysql.time_zone_leap_second OK mysql.time_zone_name OK mysql.time_zone_transition OK mysql.time_zone_transition_type OK mysql.user OK Upgrading the sys schema. Checking databases. sys.sys_config OK Upgrade process completed successfully. Checking if update is needed.执行之后才算是升级成功,登录进去发现sys库又重新出现了。
(root@localhost:mysql.sock)[(none)]>show databases; +--------------------+ | Database | +--------------------+ | information_schema | | mysql | | performance_schema | | sys | | test | +--------------------+ 5 rows in set (0.00 sec)如果在线上升级的话，mysql会将所有的表进行按照5.7的格式进行重建，但是mysql的innodb都是兼容的。所以可以使用mysql_upgrade的一个参数。
[root@elk-node03 application]# mysql_upgrade --help -s, --upgrade-system-tables Only upgrade the system tables, do not try to upgrade the data.使用这个参数的意义就是这更新系统表，而不涉及到数据表的更新。
[root@elk-node03 application]# mysql_upgrade -s --force The --upgrade-system-tables option was used, databases won't be touched. Checking server version. Running queries to upgrade MySQL server. The sys schema is already up to date (version 1.5.1). Upgrade process completed successfully. Checking if update is needed.