mysql多版本安装1. 创建目录，创建data目录，赋权限 2. 初始化数据库 3. 启动数据库 4. 连接数据库

因客户要求升级mysql5.6版本，且服务不能停，服务器没网络环境，所以只能同时安装一个mysql8.0.22版本，对数据恢复后，再停止老服务。此处记下在同一台服务器安装第二版mysql（mysql8）的步骤

[root@MySQL-Test soft]# mv mysql-8.0.22-linux-glibc2.12-x86_64/ mysql8
[root@MySQL-Test soft]# mv mysql8/ /usr/local/
[root@MySQL-Test soft]# mkdir data
[root@MySQL-Test soft]# chown -R mysql:mysql /var/lib/mysql8
[root@MySQL-Test mysql]#chown -R mysql:mysql ./　 　                        #修改当前目录拥有者为mysql用户

2. 初始化数据库

[root@MySQL-Test mysql8]# bin/mysqld --initialize --user=mysql --basedir=/usr/local/mysql8 --datadir=/usr/local/mysql8/data
2021-01-28T17:35:34.719103Z 0 [Warning] [MY-010915] [Server] 'NO_ZERO_DATE', 'NO_ZERO_IN_DATE' and 'ERROR_FOR_DIVISION_BY_ZERO' sql modes should be used with strict mode. They will be merged with strict mode in a future release.
2021-01-28T17:35:34.719186Z 0 [System] [MY-013169] [Server] /usr/local/mysql8/bin/mysqld (mysqld 8.0.22) initializing of server in progress as process 2776
2021-01-28T17:35:34.720308Z 0 [Warning] [MY-013242] [Server] --character-set-server: 'utf8' is currently an alias for the character set UTF8MB3, but will be an alias for UTF8MB4 in a future release. Please consider using UTF8MB4 in order to be unambiguous.
2021-01-28T17:35:34.725807Z 1 [System] [MY-013576] [InnoDB] InnoDB initialization has started.
2021-01-28T17:35:35.405836Z 1 [System] [MY-013577] [InnoDB] InnoDB initialization has ended.
2021-01-28T17:35:37.156546Z 6 [Note] [MY-010454] [Server] A temporary password is generated for root@localhost: -vHpdA8LOnxy

记下上面的-vHpdA8LOnxy临时密码，下面连接mysql中会用到

MySQL8.0.22的my.cnf配置（路径可自定义，建议放在$base/etc/路径下）。在启动时需要指定my.cnf文件路径

  [client]
  port = 3307
  socket = /var/lib/mysql/mysql.sock
  # The MySQL server
  [mysqld]
  default-authentication-plugin=mysql_native_password   #MySQL8的加密规则改变，如果要用老版的，需要加此句
  port = 3307
  mysqlx_port = 33070
  user = root
  socket = /var/lib/mysql/mysql.sock
  mysqlx_socket=/var/lib/mysql/mysqlx.sock
  pid-file = /usr/local/DBdatas/mysql8/mysql.pid
  basedir = /usr/local/DBdatas/mysql8/
  datadir = /usr/local/DBdatas/mysql8/data
  tmpdir = /usr/local/DBdatas/mysql8/tmp
  open_files_limit = 60000
  explicit_defaults_for_timestamp
  server-id = 1203307
  lower_case_table_names = 1
  character-set-server = utf8mb4
  federated
  #sql_mode=STRICT_TRANS_TABLES
  max_connections = 1000
  max_connect_errors = 100000
  interactive_timeout = 86400
  wait_timeout = 86400
  back_log=100
  default-storage-engine = InnoDB
  #skip-grant-tables
  #*********** GTID settting*******************
  log_slave_updates = 1
  gtid_mode=ON
  enforce-gtid-consistency=true
  innodb_flush_log_at_trx_commit=2
  binlog_format= row
  skip-slave-start=1
  sync_binlog=5
  #*********** Logs related settings ***********
  #log-bin = /usr/local/DBdatas/mysql8/log/binlog/mysql-bin
  #binlog_cache_size=32m
  #max_binlog_cache_size=64m
  #max_binlog_size=512m
  long_query_time = 1
  log_output = FILE
  log-error = /usr/local/DBdatas/mysql8/log/mysql-error.log
  #slow_query_log = 1
  #slow_query_log_file = /usr/local/DBdatas/mysql8/log/slow_statement.log
  #log_queries_not_using_indexes
  #general_log = 0
  #general_log_file = /usr/local/DBdatas/mysql8/log/general_statement.log
  #expire-logs-days = 14
  #binlog_expire_logs_seconds = 1728000
  #relay-log = /usr/local/DBdatas/mysql8/log/binlog/relay-bin
  #relay-log-index = /usr/local/DBdatas/mysql8/log/binlog/relay-bin.index
  #****** MySQL Replication New Feature********* 
  #master-info-repository=TABLE
  #relay-log-info-repository=TABLE
  #relay-log-recovery
  #*********** INNODB Specific options *********** 
  innodb_buffer_pool_size = 2048M
  transaction-isolation=REPEATABLE-READ
  innodb_buffer_pool_instances = 8
  innodb_file_per_table = 1
  #innodb_data_home_dir = /usr/local/DBdatas/mysql8/innodb_ts
  innodb_data_home_dir = /usr/local/DBdatas/mysql8/data
  innodb_data_file_path = ibdata1:2048M:autoextend
  innodb_thread_concurrency = 8
  innodb_log_buffer_size = 16M
  innodb_log_file_size = 128M
  innodb_log_files_in_group = 3
  innodb_log_group_home_dir = /usr/local/DBdatas/mysql8/innodb_log
  innodb_flush_log_at_trx_commit = 2
  innodb_max_dirty_pages_pct = 70
  innodb_flush_method=O_DIRECT
  [mysql]
  no-auto-rehash
  default-character-set=utf8
  prompt = (\u@\h) [\d]>\_

3. 启动数据库

#启动8
/usr/local/DBdatas/mysql8/bin/mysqld_safe --defaults-file=/usr/local/DBdatas/mysql8/my.cnf --datadir=/usr/local/DBdatas/mysql8/data --socket=/var/lib/mysql/mysql.sock --basedir=/usr/local/DBdatas/mysql8 --user=mysql --port=3307

如果需要跳过密码认证，可以修改my.cnf配置文件，添加skip-grant-tables，或在启动时添加参数—-skip-grant-tables

4. 连接数据库

==注意此处需要先进入对应版本的bin目录，再连接数据库。遇到的坑为在安装8.0版本后，没有进入bin目录启动mysql8，导致启动后密码校验规则一直为caching_sha2_password，无法变更为兼容老版的mysql_native_password，导致登陆时一直报错。只有这样，在my.cnf中配置的default-authentication-plugin=mysql_native_password参数才会生效== 报错如下：查看简要规则如下：
mysql> use mysql;   --切换到mysql库
mysql>SELECT Host, User, plugin from user;

正式执行下面代码：

#因为多版本，启动时需要先进入bin目录，防止引用了其他版本的配置文件
[root@WXB-QZ-1-5 database_bak]# cd /usr/local/DBdatas/mysql8/bin/
#进入bin目录后，指定mysql8的sock文件登陆
[root@WXB-QZ-1-5 bin]# ./mysql  -u root -p -S /var/lib/mysql/mysql.sock    
Enter password:       #此处输入前面的临时密码登陆
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 8
Server version: 8.0.22

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Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql>alter user user() identified by "root";
mysql>use mysql;
# 不修改原root的localhost的远程权限，单独创建一个root@%
mysql> CREATE USER 'root'@'%' IDENTIFIED BY 'password';
mysql> ALTER USER 'root'@'%' IDENTIFIED WITH mysql_native_password BY 'password';
mysql> GRANT ALL PRIVILEGES ON *.* TO 'root'@'%' WITH GRANT OPTION ;
mysql>flush privileges;  #刷新权限