1.mysql errors:message from server: "Host 'xxx' is blocked because of many connection errors; unblock
数据库连接抛了异常：null, message from server: "Host 'PC-20130201IBXI' is blocked because of many connection errors; unblock with 'mysqladmin flush-hosts'"。
原因：同一个ip在短时间内产生太多（超过mysql数据库max_connection_errors的最大值）中断的数据库连接而导致的阻塞；解决办法如下：
mysqladmin -u root -p flush-hosts
2. MySQL 5.7.17 安装报错CMake Error at cmake/boost.cmake:81 (MESSAGE)
解决办法是：
1）.在/usr/local下创建一个名为boost的文件夹
mkdir -p /usr/local/boost
2）.进入这个新创建的文件夹然后下载boost
wget http://www.sourceforge.net/projects/boost/files/boost/1.59.0/boost_1_59_0.tar.gz
3）.解压
tar -xvzf boost_1_59_0.tar.gz
4）.继续cmake，添加上红色部分
cmake . -DCMAKE_INSTALL_PREFIX=/usr/local/mysql
-DDEFAULT_CHARSET=utf8
-DDEFAULT_COLLATION=utf8_general_ci
-DENABLED_LOCAL_INFILE=ON
-DWITH_INNOBASE_STORAGE_ENGINE=1
-DWITH_FEDERATED_STORAGE_ENGINE=1
-DWITH_BLACKHOLE_STORAGE_ENGINE=1
-DWITHOUT_EXAMPLE_STORAGE_ENGINE=1
-DWITH_PARTITION_STORAGE_ENGINE=1
-DWITH_PERFSCHEMA_STORAGE_ENGINE=1
-DCOMPILATION_COMMENT='Mysqlma'
-DWITH_READLINE=ON
-DWITH_BOOST=/usr/local/boost
-DSYSCONFDIR=/data/mysqldata/3306
-DMYSQL_UNIX_ADDR=/data/mysqldata/3306/mysql.sock
3.Mysql重启失败原因剖析一
Timeout error occurred trying to start MySQL Daemon.
当修改完某些配置之后，打算/etc/init.d/mysqld restart，发现重启失败。
首先看mysql的日志文件查找原因：tail /var/log/mysqld.log
发现为用户权限问题：
120724 15:52:02 [ERROR] /usr/libexec/mysqld: Can't create/write to file '/var/run/mysqld/mysqld.pid' (Errcode: 13)
120724 15:52:02 [ERROR] Can't start server: can't create PID file: Permission denied
120724 15:52:02 mysqld ended
========
solution
========
cd /var/lib/
ls -l | grep mysqld
看看用户名和用户组是否均为mysql，如果不是，则重新将权限调整回mysql默认值。
chown -R mysql:mysql mysqld
chmod 755 -R mysqld
现在试试重启服务：/etc/init.d/mysqld start
如果重启仍失败，则还有可能是执行文件的权限还有问题：
cd /var/run/
ls -l | grep mysqld
看看用户名和用户组是否均为mysql，如果不是，则重新将权限调整回mysql默认值。
chown -R mysql:mysql mysqld
4.mysql数据库通过yum安装后启动不了。如下：
MySQL Daemon failed to start.
Starting mysqld: [FAILED]
查看日志
[ERROR] Fatal error: Can't open and lock privilege tables: Table 'mysql.host' doesn't exist
输入mysql_install_db命令后，重启mysql成功。
[root@localhost etc]# mysql_install_db
Installing MySQL system tables...
[root@localhost etc]# service mysqld restart
Stopping mysqld: [ OK ]
Starting mysqld: [ OK ]
5.一次mysql slave故障的解决过程
mysql> show slave statusG
Last_SQL_Error: Relay log read failure: Could not parse relay log event entry. The possible reasons are: the master’s binary log is corrupted (you can check this by running ‘mysqlbinlog’ on the binary log), the slave’s relay log is corrupted (you can check this by running ‘mysqlbinlog’ on the relay log), a network problem, or a bug in the master’s or slave’s MySQL code. If you want to check the master’s binary log or slave’s relay log, you will be able to know their names by issuing ‘SHOW SLAVE STATUS’ on this slave. Error_code: 1594
看样子，应该由于网络原因 slave relay log损坏了
查看 mysql 日志：
170306 12:34:08 [Note] Slave SQL thread initialized, starting replication in log ‘mysql-bin.000033’ at position 77270703, relay log ‘./HK3ASERVER-relay-bin.066281’ position: 10604437
170306 12:34:08 [ERROR] Error in Log_event::read_log_event(): ‘read error’, data_len: 67, event_type: 19
170306 12:34:08 [ERROR] Error reading relay log event: slave SQL thread aborted because of I/O error
170306 12:34:08 [ERROR] Slave SQL: Relay log read failure: Could not parse relay log event entry. The possible reasons are: the master’s binary log is corrupted (you can check this by running ‘mysqlbinlog’ on the binary log), the slave’s relay log is corrupted (you can check this by running ‘mysqlbinlog’ on the relay log), a network problem, or a bug in the master’s or slave’s MySQL code. If you want to check the master’s binary log or slave’s relay log, you will be able to know their names by issuing ‘SHOW SLAVE STATUS’ on this slave. Error_code: 1594
170306 12:34:08 [ERROR] Error running query, slave SQL thread aborted. Fix the problem, and restart the slave SQL thread with “SLAVE START”. We stopped at log ‘mysql-bin.000033’ position 77270703
mysql> stop slave;
mysql> change master to Master_Log_File=’mysql-bin.000033’, Master_Log_Pos=77270703;
This operation cannot be performed with a running slave; run STOP SLAVE first
mysql> show slave statusG
发现IO_THREAD线程一直存在停不掉
最后，将mysql/data目录下的 master.info 备走，重新启动 mysql
mysql> show slave statusG
发现 slave 已彻底停掉了
mysql> reset slave;
mysql> change master to Master_Log_File=’mysql-bin.000033’, Master_Log_Pos=77270703;
mysql> start slave;
Slave_IO_Running: Yes
Slave_SQL_Running: Yes
slave 恢复正常
6.主从复制或主主复制时发生如下情况
Slave_IO_Running: Connecting
原因
1）网络不通
2）pos位置不对
3）repl密码不对
4) 防火墙规则阻拦或者selinux没关
5) server-id不对
7.mysql启动失败报错之一
[ERROR] Can't create interrupt-thread (error 11, errno: 11)
或
Can't create a new thread (errno 11); if you are not out of available memory, you can consult the manual for a possible OS-dependent bug'
或
InnoDB: Error: pthread_create returned 11
1.）直接处理方法，重启服务器，刷新进程连接。
2.）修改max user processes
ulimit -u 查看
修改/etc/security/limits.conf文件，添加：
* soft nofile 65535
* hard nofile 65535
* soft nproc 65535 增加max user processes
* hard nproc 65535
查看/etc/security/limits.d目录是否有文件“90-nproc.conf”，没有的话新建该文件，文件，内容写为：
* soft nproc 65535
* hard nproc 65535
退出（logout）重新登录后，使用ulimit -a查看系统参数
8.ERROR! The server quit without updating PID file (/usr/local/mysql/var/LNMP.pid)之一
[root@LNMP ~]# /etc/init.d/mysql start
Starting MySQL. ERROR! The server quit without updating PID file (/usr/local/mysql/var/LNMP.pid).
- root@LNMP var]# tail -f /usr/local/mysql/var/LNMP.err
- /usr/local/mysql/bin/mysqld: Can't create/write to file '/tmp/ibJb9vcs' (Errcode: 13)
- 161201 8:45:41 InnoDB: Error: unable to create temporary file; errno: 13
- 161201 8:45:41 [ERROR] Plugin 'InnoDB' init function returned error.
- 161201 8:45:41 [ERROR] Plugin 'InnoDB' registration as a STORAGE ENGINE failed.
- 161201 8:45:41 [ERROR] Unknown/unsupported storage engine: InnoDB
- 161201 8:45:41 [ERROR] Aborting
- 161201 8:45:41 [Note] /usr/local/mysql/bin/mysqld: Shutdown complete
- 161201 08:45:41 mysqld_safe mysqld from pid file /usr/local/mysql/var/LNMP.pid ended
再次启动mysql，mysql正常启动！
9.Starting MySQL...The server quit without updating PID file 之二
1） 问题
[root@localhost mysql]# /etc/rc.d/init.d/mysql status
MySQL is not running, but lock file (/var/lock/subsys/mysql[FAILED]
[root@localhost mysql]# /etc/rc.d/init.d/mysql start
Starting MySQL...The server quit without updating PID file (/usr/local/mysql/data/localhost.localdomain.pid). [FAILED]
2 ）原因
没有初始化权限表
3 ）解决办法
#cd /usr/local/mysql（进入mysql安装目录）
#chown -R mysql.mysql .
#su - mysql
$cd server
$scripts/mysql_install_db
4 ）解决过程
[root@localhost ~]# cd /usr/local/mysql
[root@localhost mysql]# chown -R mysql.mysql .
[root@localhost mysql]# su - mysql
[mysql@localhost ~]$ cd /usr/local/mysql
[mysql@localhost mysql]$ scripts/mysql_install_db
Installing MySQL system tables...
OK
Filling help tables...
OK
To start mysqld at boot time you have to copy
support-files/mysql.server to the right place for your system
PLEASE REMEMBER TO SET A PASSWORD FOR THE MySQL root USER !
To do so, start the server, then issue the following commands:
./bin/mysqladmin -u root password 'new-password'
./bin/mysqladmin -u root -h localhost.localdomain password 'new-password'
Alternatively you can run:
./bin/mysql_secure_installation
which will also give you the option of removing the test
databases and anonymous user created by default. This is
strongly recommended for production servers.
See the manual for more instructions.
You can start the MySQL daemon with:
cd . ; ./bin/mysqld_safe &
You can test the MySQL daemon with mysql-test-run.pl
cd ./mysql-test ; perl mysql-test-run.pl
Please report any problems with the ./bin/mysqlbug script!
[mysql@localhost mysql]$ /usr/local/mysql/bin/mysqld_safe --user=mysql &
[1] 11767
[mysql@localhost mysql]$ 120502 07:01:17 mysqld_safe Logging to '/usr/local/mysql/data/localhost.localdomain.err'.
120502 07:01:17 mysqld_safe Starting mysqld daemon with databases from /usr/local/mysql/data
[mysql@localhost mysql]$ /etc/rc.d/init.d/mysql status
MySQL running (11830) [ OK ]
[mysql@localhost mysql]$ /etc/rc.d/init.d/mysql start
Starting MySQL [ OK ]
10.Starting MySQL.. ERROR! The server quit without updating PID file (/var/lib/mysql/localhost.localdomain.pid)之三
起因：在VM 上将一数据库的数据文件（/var/lib/mysql整个文件夹）拷贝到另外一台VM上，然后新的VM 上启动MYSQL，结果报如下异常：(提示：冷备务必保证关闭服务)
[root@localhost mysql]# service mysql start
Starting MySQL.. ERROR! The server quit without updating PID file (/var/lib/mysql/localhost.localdomain.pid).
大部分的答案都是：
1）. 注释/etc/my.cnf里的skip-federated注释掉即#skip-federated；
2）. my.cnf文件配置过高，重新定义其中的参数（根据服务器情况定义）；
3）. 杀掉mysql_safe和mysqld进程，然后再重启；
4）. 当前日志文件过大，超出了my.cnf中定义的大小（默认为64M），删除日志文件再重启；
5）. 其他情况，查看日志文件（我的是localhost.localdomain.err，具体因人而异），然后具体分析；
问题解决：
其中，查看了日志内容，如下：
[root@localhost mysql]# less localhost.localdomain.err
111203 22:09:03 mysqld_safe Starting mysqld daemon with databases from /var/lib/mysql
^G/usr/sbin/mysqld: File './mysql-bin.index' not found (Errcode: 13)
111203 22:09:03 [ERROR] Aborting
111203 22:09:03 [Note] /usr/sbin/mysqld: Shutdown complete
111203 22:09:03 mysqld_safe mysqld from pid file /var/lib/mysql/localhost.localdomain.pid ended
但是我查看了我的目录文件，mysql-bin.index文件是存在的呀，奇怪：
[root@localhost mysql]# ll
total 49828
-rw-rw----. 1 mysql mysql 35651584 Dec 3 17:55 ibdata1
-rw-rw----. 1 mysql mysql 5242880 Dec 3 17:55 ib_logfile0
-rw-rw----. 1 mysql mysql 5242880 Dec 3 15:45 ib_logfile1
-rw-rw----. 1 mysql root 1376 Dec 3 22:02 localhost.localdomain.err
drwx--x--x. 2 mysql mysql 4096 Dec 3 17:55 mysql
-rw-rw----. 1 mysql mysql 4847020 Dec 3 17:55 mysql-bin.000001
-rw-rw----. 1 mysql mysql 1373 Dec 3 17:56 mysql-bin.000002
-rw-r--r--. 1 root root 19 Dec 3 15:38 mysql-bin.index
drwx------. 2 mysql mysql 4096 Dec 3 17:55 performance_schema
-rw-r--r--. 1 root root 116 Nov 25 21:03 RPM_UPGRADE_HISTORY
-rw-r--r--. 1 mysql mysql 116 Nov 25 21:03 RPM_UPGRADE_MARKER-LAST
drwxr-xr-x. 2 mysql mysql 4096 Dec 3 17:55 test
仔细看了下，咦？-rw-r--r--. 1 root root 19 Dec 3 15:38 mysql-bin.index----难道是权限不够？于是将该文件加了写权限，重启，涛声依旧！！！噢噢！
难道是编码问题？难道是....继续猜测。。。问题还是没解决，后来我做了一件事情，将mysql-bin.index文件删除掉！或者修改其所有者所有组，重启！
[root@localhost mysql]# rm -rf mysql-bin.index
[root@localhost mysql]#
[root@localhost mysql]# service mysql start
Starting MySQL... SUCCESS!
补充：
很多时候，我们在做主从同步的时候，将数据库目录整体打包拷贝到从机上的时候，重启也往往会出现类似的问题，解决方法仍然是：
1）给MYSQL数据库数据目录权限：chown -R mysql:mysql 目录名称
2）务必保证MYSQL的进程是已经关闭了的；
另外要注意的地方就是：ib_*, mysql-bin-*, *.err(log文件)以及master-info和relay-info文件都是可以删除的，相当于重新初始化数据库的数据，但是前提是：
1）操作前要先关掉MYSQL的进程；
2）删掉文件后要重新启动MYSQL，如果有异常，请自行查看日志找问题，一般都比较好定位和解决。
11.The server quit without updating PID file (/var/lib/mysql/tserver.pid).[FAILED] 之四
查看日志
[ERROR] InnoDB: auto-extending data file ./ibdata1 is of a different size 640 pages (rounded down to MB) than specified in the .cnf file: initial 768 pages, max 0 (relevant if non-zero) pages!
[ERROR] InnoDB: Could not open or create the system tablespace. If you tried to add new data files to the system tablespace, and it failed here, you should now edit innodb_data_file_path in my.cnf back to what it was, and remove the new ibdata files InnoDB created in this failed attempt. InnoDB only wrote those files full of zeros, but did not yet use them in any way. But be careful: do not remove old data files which contain your precious data!
[ERROR] Plugin 'InnoDB' init function returned error.
[ERROR] Plugin 'InnoDB' registration as a STORAGE ENGINE failed.
[ERROR] Unknown/unsupported storage engine: InnoDB
[ERROR] Aborting
解决办法：
删除了如下三个文件：
[root@tserver mysql]# rm ibdata1 ib_logfile0 ib_logfile1
rm: remove regular file `ibdata1'? yes
rm: remove regular file `ib_logfile0'? yes
rm: remove regular file `ib_logfile1'? yes
重启 OK
12.启动报错 Neither host 'localhost.localdomain' nor 'localhost' could be looked up with...
解决方法：
查看cat /etc/hosts 发现什么文件也没有，编辑内容相关配置。
vim /etc/hosts 输入以下内容：127.0.0.1localhost.localdomain localhost
重启 OK
13.在执行scripts/mysql_install_db --user=mysql --basedir=/usr/local/mysql --datadir=/data/mysqldb命令时一直报错：
Can't locate Data/Dumper.pm in @INC (@INC contains: /usr/local/lib64/perl5 /usr/local/share/perl5 /usr/lib64/perl5/vendor_perl /usr/share/perl5/vendor_perl /usr/lib64/perl5 /usr/share/perl5 .)
at scripts/mysql_install_db line 42. BEGIN failed--compilation aborted at scripts/mysql_install_db line 42.
原因:
Fedora 19中yum的prel包中没有Dumper.pm文件。这时候只要执行以下命令就可以手动下载Dumper.pm文件
yum install 'perl(Data::Dumper)'
14.手动删除binlog日志后启动失败，报错如下：
Failed to open log (file './mysql-bin.000002', errno 2)
2018-01-16 13:59:13 4084 [ERROR] Could not open log file
2018-01-16 13:59:13 4084 [ERROR] Can't init tc log
解决办法：删除binlog索引文件
rm -rf mysql-bin.index
然后重启即可
15.CentOS7.2默认安装mariadb-server
报错：Failed to start mysqld.service: Unit not
found
当输入命令
~]# systemctl start mysql.service
要启动MySQL数据库是却是这样的提示
Failed to start mysqld.service: Unit not found
原因：
CentOS 7的yum源中貌似没有正常安装mysql时的mysql-sever文件，需要去官网上下载
解决方法如下:
方法一：（常用+实用）
wget http://dev.mysql.com/get/mysql-community-release-el7-5.noarch.rpm
rpm -ivh mysql-community-release-el7-5.noarch.rpm
service mysqld start
方法二：
首先需要安装mariadb-server
~]# yum install -y mariadb-server
启动服务
~]# systemctl start mariadb.service
添加到开机启动
~]# systemctl enable mariadb.service
进行一些安全设置，以及修改数据库管理员密码
~]# mysql_sceure_installation
至此完成!
可以测试一下
~]# mysql -u root -p
后续积累中....