[問題現象]
服務器在運行過程中，因人為意外導致電源被拔，服務器宕機，mysql重啟不成功，報錯如下
根據提示，輸入systemctl status mysql.service和journalctl -xe查看日志，經過一番百度谷歌折騰也是無果。（很多時候，不能因為突發事件就“病急亂投醫”）
最后在mysql 的日志處看到了報錯日志
如果centos是通過yum安裝的mysql，那么日志一般在/var/log/mysql.log
查看到日志
2018-11-29T08:39:18.977374Z 0 [Warning] TIMESTAMP with implicit DEFAULT value is deprecated. Please use --explicit_defaults_for_timestamp server option (see documentation for more details).
2018-11-29T08:39:18.978051Z 0 [Note] /usr/sbin/mysqld (mysqld 5.7.22) starting as process 11192 ...
2018-11-29T08:39:18.979893Z 0 [Note] InnoDB: PUNCH HOLE support available
2018-11-29T08:39:18.979910Z 0 [Note] InnoDB: Mutexes and rw_locks use GCC atomic builtins
2018-11-29T08:39:18.979914Z 0 [Note] InnoDB: Uses event mutexes
2018-11-29T08:39:18.979916Z 0 [Note] InnoDB: GCC builtin __atomic_thread_fence() is used for memory barrier
2018-11-29T08:39:18.979918Z 0 [Note] InnoDB: Compressed tables use zlib 1.2.3
2018-11-29T08:39:18.979920Z 0 [Note] InnoDB: Using Linux native AIO
2018-11-29T08:39:18.980073Z 0 [Note] InnoDB: Number of pools: 1
2018-11-29T08:39:18.980135Z 0 [Note] InnoDB: Using CPU crc32 instructions
2018-11-29T08:39:18.981011Z 0 [Note] InnoDB: Initializing buffer pool, total size = 128M, instances = 1, chunk size = 128M
2018-11-29T08:39:18.985294Z 0 [Note] InnoDB: Completed initialization of buffer pool
2018-11-29T08:39:18.986268Z 0 [Note] InnoDB: If the mysqld execution user is authorized, page cleaner thread priority can be changed. See the man page of setpriority().
2018-11-29T08:39:18.997726Z 0 [Note] InnoDB: Highest supported file format is Barracuda.
2018-11-29T08:39:18.998629Z 0 [Note] InnoDB: Log scan progressed past the checkpoint lsn 23732273189
2018-11-29T08:39:18.998641Z 0 [Note] InnoDB: Doing recovery: scanned up to log sequence number 23732273507
2018-11-29T08:39:18.998881Z 0 [Note] InnoDB: Database was not shutdown normally!
2018-11-29T08:39:18.998887Z 0 [Note] InnoDB: Starting crash recovery.
2018-11-29T08:39:19.110899Z 0 [Note] InnoDB: Removed temporary tablespace data file: "ibtmp1"
2018-11-29T08:39:19.110915Z 0 [Note] InnoDB: Creating shared tablespace for temporary tables
2018-11-29T08:39:19.110957Z 0 [Note] InnoDB: Setting file './ibtmp1' size to 12 MB. Physically writing the file full; Please wait ...
2018-11-29T08:39:19.149162Z 0 [Note] InnoDB: File './ibtmp1' size is now 12 MB.
2018-11-29T08:39:19.149810Z 0 [Note] InnoDB: 96 redo rollback segment(s) found. 96 redo rollback segment(s) are active.
2018-11-29T08:39:19.149818Z 0 [Note] InnoDB: 32 non-redo rollback segment(s) are active.
2018-11-29T08:39:19.150158Z 0 [Note] InnoDB: Waiting for purge to start
2018-11-29 16:39:19 0x7f1219ffb700 InnoDB: Assertion failure in thread 139715722327808 in file fut0lst.ic line 85
InnoDB: Failing assertion: addr.page == FIL_NULL || addr.boffset >= FIL_PAGE_DATA
InnoDB: We intentionally generate a memory trap.
InnoDB: Submit a detailed bug report to http://bugs.mysql.com.
InnoDB: If you get repeated assertion failures or crashes, even
InnoDB: immediately after the mysqld startup, there may be
InnoDB: corruption in the InnoDB tablespace. Please refer to
InnoDB: http://dev.mysql.com/doc/refman/5.7/en/forcing-innodb-recovery.html
InnoDB: about forcing recovery.
08:39:19 UTC - mysqld got signal 6 ;
This could be because you hit a bug. It is also possible that this binary
or one of the libraries it was linked against is corrupt, improperly built,
or misconfigured. This error can also be caused by malfunctioning hardware.
Attempting to collect some information that could help diagnose the problem.
As this is a crash and something is definitely wrong, the information
collection process might fail.
通過搜索
InnoDB: Failing assertion: addr.page == FIL_NULL || addr.boffset >= FIL_PAGE_DATA
了解到，大部分都是因為服務器在數據庫沒用停止服務的情況下宕機，導致數據丟失
解決方法有倆個：
1、如果是大佬，則繼續深入踩坑研究，運氣好能在google查到相似問題解決方案（反正我是沒查到
2、直接備份數據庫，然后初始化數據庫后進行恢復數據
[問題原因]
服務器宕機導致innodb的數據和實際數據庫的數據不一致，在啟動的時候就報錯了
[解決方法]
1. Forcing InnoDB Recovery
在 /etc/my.cnf中添加如下配置：
[mysqld]
innodb_force_recovery = 1
其中后面的值設置為1、如果1不能啟動成功，再逐步增加為2/3/4等。直到能啟動mysql為止！！！
重啟成功后，測試數據庫是否可以正常連接：
mysql -u root -p 123456
能連進去的話就exit退出
2.數據備份
找一個自己找得到的目錄做數據備份
mysqldump -u root -p 123456 --all-databases > all_mysql_backup.sql
3.初始化數據庫
mysqld --initialize
啟動數據庫
service mysqld start
如果報錯，則顯得去刪除mysql的data目錄
這里的data目錄實際就是你數據庫存放的目錄，比如知道的/var/lib/mysql
4.數據恢復
登錄數據庫
mysql -u root -p 123456
恢復
source /備份目錄/all_mysql_backup.sql