mysql被误删之后如何重新安装并恢复数据
如果数据库被自己或者其他软件安装时给莫名其妙的删掉了，例如：
Removing mysql-server-core-5.7 (5.7.20-0ubuntu0.16.04.1) ...
这种会导致原本的Mysql被删除掉了，而原本的数据没有进行备份。使用“nmap”工具扫描本地127.0.0.1结果如下：
Starting Nmap 7.01 ( https://nmap.org ) at 2018-05-11 12:37 CST
Nmap scan report for localhost (127.0.0.1)
Host is up (0.000054s latency).
Not shown: 997 closed ports
PORT STATE SERVICE
22/tcp open ssh
25/tcp open smtp
111/tcp open rpcbind
会发现3306默认端口号已经消失了，而查看系统内的mysql版本却是存在的：
ubuntu@VM-164-254-ubuntu:/$ mysql -V
mysql Ver 14.14 Distrib 5.7.20, for Linux (x86_64) using EditLine wrapper
查看Mysql的配置文件：
ubuntu@VM-164-254-ubuntu:/$ locate mysql.conf
/etc/init/mysql.conf
/etc/mysql/mysql.conf.d
/etc/mysql/mysql.conf.d/mysqld.cnf
/etc/mysql/mysql.conf.d/mysqld_safe_syslog.cnf
也是存在的，所以，我们完全可以在不改变原来Mysql配置文件的情况下，重装Mysql：
以ubuntu为例：
1. sudo apt-get install mysql-server
2. apt-get isntall mysql-client
3. sudo apt-get install libmysqlclient-dev
在使用第一行安装mysql-server的时候，会发现，mysql自动会将之前的数据加入进来，如下：
ubuntu@VM-164-254-ubuntu:/$ sudo apt-get install mysql-server
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following additional packages will be installed:
apparmor libcgi-fast-perl libcgi-pm-perl libencode-locale-perl libevent-core-2.0-5 libfcgi-perl libhtml-parser-perl libhtml-tagset-perl libhtml-template-perl libhttp-date-perl libhttp-message-perl
libio-html-perl liblwp-mediatypes-perl libtimedate-perl liburi-perl mysql-client-5.7 mysql-server-5.7 mysql-server-core-5.7
Suggested packages:
apparmor-profiles apparmor-profiles-extra apparmor-docs apparmor-utils libdata-dump-perl libipc-sharedcache-perl libwww-perl tinyca
The following NEW packages will be installed:
apparmor libcgi-fast-perl libcgi-pm-perl libencode-locale-perl libevent-core-2.0-5 libfcgi-perl libhtml-parser-perl libhtml-tagset-perl libhtml-template-perl libhttp-date-perl libhttp-message-perl
libio-html-perl liblwp-mediatypes-perl libtimedate-perl liburi-perl mysql-server mysql-server-5.7 mysql-server-core-5.7
The following packages will be upgraded:
mysql-client-5.7
1 upgraded, 18 newly installed, 0 to remove and 258 not upgraded.
Need to get 12.7 MB of archives.
After this operation, 98.5 MB of additional disk space will be used.
Do you want to continue? [Y/n] y
Get:1 http://mirrors.tencentyun.com/ubuntu xenial-updates/main amd64 apparmor amd64 2.10.95-0ubuntu2.9 [450 kB]
Get:2 http://mirrors.tencentyun.com/ubuntu xenial-security/main amd64 mysql-client-5.7 amd64 5.7.22-0ubuntu0.16.04.1 [1,673 kB]
Get:3 http://mirrors.tencentyun.com/ubuntu xenial-security/main amd64 mysql-server-core-5.7 amd64 5.7.22-0ubuntu0.16.04.1 [7,268 kB]
Get:4 http://mirrors.tencentyun.com/ubuntu xenial-security/main amd64 libevent-core-2.0-5 amd64 2.0.21-stable-2ubuntu0.16.04.1 [70.6 kB]
Get:5 http://mirrors.tencentyun.com/ubuntu xenial-security/main amd64 mysql-server-5.7 amd64 5.7.22-0ubuntu0.16.04.1 [2,583 kB]
Get:6 http://mirrors.tencentyun.com/ubuntu xenial/main amd64 libhtml-tagset-perl all 3.20-2 [13.5 kB]
Get:7 http://mirrors.tencentyun.com/ubuntu xenial/main amd64 liburi-perl all 1.71-1 [76.9 kB]
Get:8 http://mirrors.tencentyun.com/ubuntu xenial/main amd64 libhtml-parser-perl amd64 3.72-1 [86.1 kB]
Get:9 http://mirrors.tencentyun.com/ubuntu xenial/main amd64 libcgi-pm-perl all 4.26-1 [185 kB]
Get:10 http://mirrors.tencentyun.com/ubuntu xenial/main amd64 libfcgi-perl amd64 0.77-1build1 [32.3 kB]
Get:11 http://mirrors.tencentyun.com/ubuntu xenial/main amd64 libcgi-fast-perl all 1:2.10-1 [10.2 kB]
Get:12 http://mirrors.tencentyun.com/ubuntu xenial/main amd64 libencode-locale-perl all 1.05-1 [12.3 kB]
Get:13 http://mirrors.tencentyun.com/ubuntu xenial/main amd64 libhtml-template-perl all 2.95-2 [60.4 kB]
Get:14 http://mirrors.tencentyun.com/ubuntu xenial/main amd64 libtimedate-perl all 2.3000-2 [37.5 kB]
Get:15 http://mirrors.tencentyun.com/ubuntu xenial/main amd64 libhttp-date-perl all 6.02-1 [10.4 kB]
Get:16 http://mirrors.tencentyun.com/ubuntu xenial/main amd64 libio-html-perl all 1.001-1 [14.9 kB]
Get:17 http://mirrors.tencentyun.com/ubuntu xenial/main amd64 liblwp-mediatypes-perl all 6.02-1 [21.7 kB]
Get:18 http://mirrors.tencentyun.com/ubuntu xenial/main amd64 libhttp-message-perl all 6.11-1 [74.3 kB]
Get:19 http://mirrors.tencentyun.com/ubuntu xenial-security/main amd64 mysql-server all 5.7.22-0ubuntu0.16.04.1 [10.8 kB]
Fetched 12.7 MB in 0s (16.8 MB/s)
Preconfiguring packages ...
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(Reading database ... 71503 files and directories currently installed.)
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Unpacking apparmor (2.10.95-0ubuntu2.9) ...
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update-rc.d: warning: start and stop actions are no longer supported; falling back to defaults
Skipping profile in /etc/apparmor.d/disable: usr.sbin.rsyslogd
Setting up mysql-client-5.7 (5.7.22-0ubuntu0.16.04.1) ...
Setting up mysql-server-core-5.7 (5.7.22-0ubuntu0.16.04.1) ...
Setting up libevent-core-2.0-5:amd64 (2.0.21-stable-2ubuntu0.16.04.1) ...
Setting up mysql-server-5.7 (5.7.22-0ubuntu0.16.04.1) ...
update-alternatives: using /etc/mysql/mysql.cnf to provide /etc/mysql/my.cnf (my.cnf) in auto mode
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
The sys schema is already up to date (version 1.5.1).
Checking databases.
cplusplus.goods OK
cplusplus.goods_type OK
cplusplus.guanli OK
cplusplus.jiaoyi_application OK
cplusplus.logintmp OK
cplusplus.tmp_register OK
cplusplus.transaction OK
cplusplus.user OK
cplusplus.user_property OK
cplusplus.user_renzheng OK
cplusplus.user_xinyudu OK
phpmyadmin.pma__bookmark OK
phpmyadmin.pma__central_columns OK
phpmyadmin.pma__column_info OK
phpmyadmin.pma__designer_settings OK
phpmyadmin.pma__export_templates OK
phpmyadmin.pma__favorite OK
phpmyadmin.pma__history OK
phpmyadmin.pma__navigationhiding OK
phpmyadmin.pma__pdf_pages OK
phpmyadmin.pma__recent OK
phpmyadmin.pma__relation OK
phpmyadmin.pma__savedsearches OK
phpmyadmin.pma__table_coords OK
phpmyadmin.pma__table_info OK
phpmyadmin.pma__table_uiprefs OK
phpmyadmin.pma__tracking OK
phpmyadmin.pma__userconfig OK
phpmyadmin.pma__usergroups OK
phpmyadmin.pma__users OK
sys.sys_config OK
安装好数据库并打开服务之后查看原来的数据库是存在的，
ubuntu@VM-164-254-ubuntu:/$ mysql -uroot -p
Enter password:
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 4
Server version: 5.7.22-0ubuntu0.16.04.1 (Ubuntu)
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.
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| cplusplus |
| mysql |
| performance_schema |
| phpmyadmin |
| sys |
| xiaozu |
| xinzu |
+--------------------+
8 rows in set (0.00 sec)
使用nmap的结果：
ubuntu@VM-164-254-ubuntu:/$ nmap 127.0.0.1
Starting Nmap 7.01 ( https://nmap.org ) at 2018-05-11 13:02 CST
Nmap scan report for localhost (127.0.0.1)
Host is up (0.000055s latency).
Not shown: 993 closed ports
PORT STATE SERVICE
22/tcp open ssh
25/tcp open smtp
80/tcp open http
111/tcp open rpcbind
3306/tcp open mysql
8011/tcp open unknown
8081/tcp open blackice-icecap
Nmap done: 1 IP address (1 host up) scanned in 0.06 seconds
所以被误删了数据库只需要重装mysql就行了，mysql会自动导入原本的数据表和使用原本的配置