debian/Ubuntu下，安装／平滑升级 MySQL 到 5.7(建议不要搞编译安装，编译安装太费事了，还可能搞不定）

wget http://dev.mysql.com/get/mysql-apt-config_0.8.1-1_all.deb
dpkg -i mysql-apt-config_0.8.1-1_all.deb
需要注意的是在添加源那一步的时候，会叫你选择安装 MySQL 哪个应用，这里选择 Server 即可，再选择 MySQL 5.7 后又会回到选择应用的那个界面，此时选择ok即可。

apt-get update
apt-get install mysql-server (此时，安装的mysql-server的版本就是5.7版而非5.5
版）

如果提示：mysqld: Can’t create/write to file ‘/var/lib/mysql/is_writable’，试着执行：
chown mysql /var/lib/mysql
chgrp mysql /var/lib/mysql

root@ary:~# mysql --version
mysql  Ver 14.14 Distrib 5.7.18, for Linux (x86_64) using  EditLine wrapper
root@ary:~#
配置文件在/etc/mysql/里面。

安装完之后还需执行一下:mysql_upgrade -u root -pyour_pw 更新数据（重要.如果你以前安装了mysql)

一般会出现一点小插曲。我在 MySQL 自动启动的时候起不来了：

也没看见日志在哪儿，在 /etc/mysql 目录下找日志的时候发现多了个 my.cnf.dpkg-dist 文件，对比一下发现和原来的 my.cnf 不太一样呀，把原来的 my.cnf 备份后使用这个文件替换掉。再次启动 MySQL 果然 OK 了。


参考https://dev.mysql.com/doc/mysql-apt-repo-quick-guide/en/
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关于配置优化，介绍一个好网站：http://tools.percona.com/ (Free online productivity tools for MySQL DBAs, SysAdmins and Developers)。我 1 CPU，1 GB RAM 的配置如下：

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# Generated by Percona Configuration Wizard (http://tools.percona.com/) version REL5-20120208 # Configuration name iyaozhen.com generated for pop59461@126.com at 2015-10-29 17:12:28 # # The MySQL Community Server configuration file. # # For explanations see # http://dev.mysql.com/doc/refman/5.7/en/server-system-variables.html   [mysql]   # CLIENT # port                           = 3306 socket                         = /var/run/mysqld/mysqld.sock   [mysqld_safe] pid-file                       = /var/run/mysqld/mysqld.pid socket                         = /var/run/mysqld/mysqld.sock nice                           = 0   [mysqld]   # GENERAL # user                           = mysql default-storage-engine         = InnoDB pid-file                       = /var/run/mysqld/mysqld.pid socket                         = /var/run/mysqld/mysqld.sock port                           = 3306 basedir                        = /usr datadir                        = /var/lib/mysql tmpdir                         = /tmp lc-messages-dir                = /usr/share/mysql explicit_defaults_for_timestamp   # Disabling symbolic-links is recommended to prevent assorted security risks symbolic-links                 = 0   # Instead of skip-networking the default is now to listen only on # localhost which is more compatible and is not less secure. bind-address                   = 127.0.0.1   # MyISAM # key-buffer-size                = 32M   # SAFETY # max-allowed-packet             = 16M sysdate-is-now                 = 1 skip-name-resolve   # CACHES AND LIMITS # tmp-table-size                 = 32M max-heap-table-size            = 32M query-cache-type               = 0 query-cache-size               = 0 max-connections                = 500 thread-cache-size              = 50 open-files-limit               = 65535 table-definition-cache         = 1024 table-open-cache               = 2048   # INNODB # innodb-flush-method            = O_DIRECT innodb-log-files-in-group      = 2 innodb-log-file-size           = 64M innodb-flush-log-at-trx-commit = 2 innodb-file-per-table          = 1 innodb-buffer-pool-size        = 768M   # LOGGING # log-error                      = /var/log/mysql/error.log log-queries-not-using-indexes  = 1 slow-query-log                 = 1 slow-query-log-file            = /var/log/mysql/slow-query.log

我在启动的时候，查看 error.log 日志，发现了一些错误，下面是其解决方法：
[Warning] Could not increase number of max_open_files to more than 4096 (request: 65535)
解决办法：vim /etc/security/limits.conf，然后添加几行：

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mysql soft  nofile 65535 mysql hard  nofile 65535 www-data soft  nofile 65535 www-data hard  nofile 65535

目的是增大文件打开数，提升一定的性能，适当即可。
plugin load error:

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[ERROR] Function 'archive' already exists [Warning] Couldn't load plugin named 'archive' with soname 'ha_archive.so'. [ERROR] Function 'blackhole' already exists [Warning] Couldn't load plugin named 'blackhole' with soname 'ha_blackhole.so'. [ERROR] Function 'federated' already exists [Warning] Couldn't load plugin named 'federated' with soname 'ha_federated.so'. [ERROR] Function 'innodb' already exists [Warning] Couldn't load plugin named 'innodb' with soname 'ha_innodb.so'.

解决办法：看样子是这几个插件已经内置了，无需加载。查看 plugin 表里面也就这几个插件：

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mysql> select * from mysql.plugin; +-----------+-----------------+ | name      | dl              | +-----------+-----------------+ | archive   | ha_archive.so   | | blackhole | ha_blackhole.so | | federated | ha_federated.so | | innodb    | ha_innodb.so    | +-----------+-----------------+

直接 truncate mysql.plugin 即可。
[Warning] CA certificate ca.pem is self signed.
解决办法：这个警告是因为使用了自签证书（猜测），即使开启传输加密也有被中间人攻击的风险，可以买个权威 CA 机构颁发的证书。我们这里就直接忽略这个错误了。
[Warning] ‘user’ entry ‘root@localhost’ ignored in –skip-name-resolve mode.
解决办法：这个可以忽略，因为我们设置 skip-name-resolve，禁用了 DNS 查询。（If you have a very slow DNS and many hosts, you might be able to improve performance either by disabling DNS lookups with –skip-name-resolve or by increasing the value of host_cache_size to make the host cache larger.）
启动的时候显示 “No directory, logging in with HOME=/”。
解决办法：这是 MySQL 的命令行日志，日志路径由环境变量 MYSQL_HISTFILE 指定。若系统中没有此环境变量，就会默认在 ~ （当前用户根目录）下生成 .mysql_history 隐藏文件，类似于 .bash_history，有一定的安全风险。如果你不想要这个文件，除了修改环境变量 MYSQL_HISTFILE 外，还有一个比较好的方式就是将文件软链接到 /dev/null（ln -s /dev/null $HOME/.mysql_history）。
参考资料：
《A Quick Guide to Using the MySQL APT Repository》http://dev.mysql.com/doc/mysql-apt-repo-quick-guide/en/
《Changes Affecting Upgrades to MySQL 5.7》https://dev.mysql.com/doc/refman/5.7/en/upgrading-from-previous-series.html
http://dba.stackexchange.com/questions/65397/error-function-innodb-already-exists
https://dev.mysql.com/doc/refman/5.7/en/mysql-logging.html