mysql 关机启动不起来。
又不报错
环境：
centos 7
mysql 5.6.25
log-error=/var/log/mysqld.log
pid-file=/var/run/mysqld/mysqld.pid[root@WIN-P11PIHOSG63 ~]# tail -20 /var/log/mysqld.log
2016-03-04 14:02:31 5201 [Note] Shutting down plugin 'INNODB_LOCKS'
2016-03-04 14:02:31 5201 [Note] Shutting down plugin 'INNODB_TRX'
2016-03-04 14:02:31 5201 [Note] Shutting down plugin 'InnoDB'
2016-03-04 14:02:31 5201 [Note] InnoDB: FTS optimize thread exiting.
2016-03-04 14:02:31 5201 [Note] InnoDB: Starting shutdown...
2016-03-04 14:02:33 5201 [Note] InnoDB: Shutdown completed; log sequence number 808362591
2016-03-04 14:02:33 5201 [Note] Shutting down plugin 'PERFORMANCE_SCHEMA'
2016-03-04 14:02:33 5201 [Note] Shutting down plugin 'ARCHIVE'
2016-03-04 14:02:33 5201 [Note] Shutting down plugin 'BLACKHOLE'
2016-03-04 14:02:33 5201 [Note] Shutting down plugin 'MEMORY'
2016-03-04 14:02:33 5201 [Note] Shutting down plugin 'CSV'
2016-03-04 14:02:33 5201 [Note] Shutting down plugin 'MyISAM'
2016-03-04 14:02:33 5201 [Note] Shutting down plugin 'MRG_MYISAM'
2016-03-04 14:02:33 5201 [Note] Shutting down plugin 'sha256_password'
2016-03-04 14:02:33 5201 [Note] Shutting down plugin 'mysql_old_password'
2016-03-04 14:02:33 5201 [Note] Shutting down plugin 'mysql_native_password'
2016-03-04 14:02:33 5201 [Note] Shutting down plugin 'binlog'
2016-03-04 14:02:33 5201 [Note] /usr/sbin/mysqld: Shutdown complete
160304 14:02:34 mysqld_safe mysqld from pid file /var/run/mysqld/mysqld.pid ended
[root@WIN-P11PIHOSG63 ~]# ls -ld /var/run/mysqld/
my.cnf
[mysqld]
#
# Remove leading # and set to the amount of RAM for the most important data
# cache in MySQL. Start at 70% of total RAM for dedicated server, else 10%.
# innodb_buffer_pool_size = 128M
#
# Remove leading # to turn on a very important data integrity option: logging
# changes to the binary log between backups.
# log_bin
#
# Remove leading # to set options mainly useful for reporting servers.
# The server defaults are faster for transactions and fast SELECTs.
# Adjust sizes as needed, experiment to find the optimal values.
# join_buffer_size = 128M
# sort_buffer_size = 2M
# read_rnd_buffer_size = 2M
basedir=/usr
datadir=/var/lib/mysql
tmpdir=/tmp
socket=/var/lib/mysql/mysql.sock
#slave_load_tmpdir=/tmp
#symbolic-links=0
#skip-name-resolve
##skip-symbolic-links
#max_connect_errors = 10000
#max_connections = 500
#wait-timeout = 30
#new add dba
#binlog-format=ROW
#log-bin=master-bin
#log-slave-updates=true
#gtid-mode=on
#enforce-gtid-consistency=true
#master-info-repository=TABLE
#relay-log-info-repository=TABLE
#sync-master-info=1
#slave-parallel-workers=2
#binlog-checksum=CRC32
#master-verify-checksum=1
#slave-sql-verify-checksum=1
#binlog-rows-query-log_events=1
server-id=1
#report-port=3306
port=3306
#report-host=WIN-P11PIHOSG63.lan
#rpl_semi_sync_master_enabled=ON
# Recommended in standard MySQL setup
sql_mode=NO_ENGINE_SUBSTITUTION,STRICT_TRANS_TABLES
解决：
[mysqld_safe]
log-error=/var/log/mysqld.log
#pid-file=/var/run/mysqld/mysqld.pid #注释掉这行
service mysqld start
或者
/bin/systemctl start mysqld.service
赠送思路：
今天，启动MySQL服务器失败，如下所示：
[root@spark01 ~]# /etc/init.d/mysqld start Starting mysqld (via systemctl): Job for mysqld.service failed because the control process exited with error code. See "systemctl status mysqld.service" and "journalctl -xe" for details. [FAILED]
根据提示，分别使用systemctl status mysqld.service和journalctl -xe查看服务启动失败的原因
[root@spark01 ~]# systemctl status mysqld.service
?.mysqld.service - SYSV: MySQL database server. Loaded: loaded (/etc/rc.d/init.d/mysqld) Active: failed (Result: exit-code) since Wed 2016-01-20 18:26:57 CST; 40s ago Docs: man:systemd-sysv-generator(8) Process: 2979 ExecStart=/etc/rc.d/init.d/mysqld start (code=exited, status=1/FAILURE) Jan 20 18:26:56 spark01 systemd[1]: Starting SYSV: MySQL database server.... Jan 20 18:26:57 spark01 mysqld[2979]: MySQL Daemon failed to start. Jan 20 18:26:57 spark01 mysqld[2979]: Starting mysqld: [FAILED] Jan 20 18:26:57 spark01 systemd[1]: mysqld.service: control process exited, code=exited status=1 Jan 20 18:26:57 spark01 systemd[1]: Failed to start SYSV: MySQL database server.. Jan 20 18:26:57 spark01 systemd[1]: Unit mysqld.service entered failed state. Jan 20 18:26:57 spark01 systemd[1]: mysqld.service failed.
[root@spark01 ~]# journalctl -xe
-- -- Unit session-2.scope has begun starting up. Jan 20 18:26:48 spark01 sshd[2916]: pam_unix(sshd:session): session opened for user spark by (uid=0) Jan 20 18:26:52 spark01 su[2944]: (to root) spark on pts/1 Jan 20 18:26:52 spark01 su[2944]: pam_unix(su-l:session): session opened for user root by spark(uid=1000) Jan 20 18:26:56 spark01 polkitd[909]: Registered Authentication Agent for unix-process:2974:117137 (system bus name :1.25 Jan 20 18:26:56 spark01 systemd[1]: Starting SYSV: MySQL database server.... -- Subject: Unit mysqld.service has begun start-up -- Defined-By: systemd -- Support: http://lists.freedesktop.org/mailman/listinfo/systemd-devel -- -- Unit mysqld.service has begun starting up. Jan 20 18:26:57 spark01 mysqld[2979]: MySQL Daemon failed to start. Jan 20 18:26:57 spark01 mysqld[2979]: Starting mysqld: [FAILED] Jan 20 18:26:57 spark01 systemd[1]: mysqld.service: control process exited, code=exited status=1 Jan 20 18:26:57 spark01 systemd[1]: Failed to start SYSV: MySQL database server.. -- Subject: Unit mysqld.service has failed -- Defined-By: systemd -- Support: http://lists.freedesktop.org/mailman/listinfo/systemd-devel -- -- Unit mysqld.service has failed. -- -- The result is failed. Jan 20 18:26:57 spark01 systemd[1]: Unit mysqld.service entered failed state. Jan 20 18:26:57 spark01 systemd[1]: mysqld.service failed. Jan 20 18:26:57 spark01 polkitd[909]: Unregistered Authentication Agent for unix-process:2974:117137 (system bus name :1.
但，可惜的时，这些信息并不能提供服务启动失败的真正原因。
这时候，不妨打开MySQL的告警日志，毕竟，只要MySQL服务启动，告警日志都会有输出信息的，果然
2016-01-20T10:00:19.935771Z 0 [ERROR] /usr/sbin/mysqld: Can't create/write to file '/var/run/mysqld/mysqld.pid' (Errcode: 2 - No such file or directory) 2016-01-20T10:00:19.935795Z 0 [ERROR] Can't start server: can't create PID file: No such file or directory 160120 18:00:20 mysqld_safe mysqld from pid file /var/run/mysqld/mysqld.pid ended
MySQL服务在启动的时候，不能创建pid文件。
在终端看一下该目录是否存在，果然，不存在。
于是，创建了/var/run/mysqld/目录，重启MySQL服务
[root@spark01 ~]# mkdir -p /var/run/mysqld/
[root@spark01 ~]# /etc/init.d/mysqld start
Starting mysqld (via systemctl): Job for mysqld.service failed because the control process exited with error code. See "systemctl status mysqld.service" and "journalctl -xe" for details. [FAILED]
依旧报错，重新查看告警日志，有以下输出
2016-01-20T10:28:37.183387Z 0 [ERROR] /usr/sbin/mysqld: Can't create/write to file '/var/run/mysqld/mysqld.pid' (Errcode: 13 - Permission denied) 2016-01-20T10:28:37.183431Z 0 [ERROR] Can't start server: can't create PID file: Permission denied 160120 18:28:37 mysqld_safe mysqld from pid file /var/run/mysqld/mysqld.pid ended 160120 18:32:06 mysqld_safe Starting mysqld daemon with databases from /var/lib/mysql
原来，/var/run/mysqld/的属主和属组还是root，mysql并不能在其中创建文件，后修改该目录的属主和属组，启动OK。
[root@spark01 ~]# ls -ld /var/run/mysqld/ drwxr-xr-x 2 root root 40 Jan 20 18:28 /var/run/mysqld/ [root@spark01 ~]# chown mysql.mysql /var/run/mysqld/ [root@spark01 ~]# /etc/init.d/mysqld start Starting mysqld (via systemctl): [ OK ]
总结：
以前在玩Kubernetes的时候，常遇到启动失败的情况，根据systemctl的提示，通过systemctl status mysqld.service和journalctl -xe命令查看服务启动失败的原因往往并不如人意，反而给了一种错误的暗示，以为这个跟系统有关。其实，通过查看服务的日志，往往更能清晰的知道服务启动失败的原因。
参考：
http://www.cnblogs.com/ivictor/p/5146247.html
