sudo kill -STOP $(cat /var/run/mysqld/mysqld.pid)

sudo kill -CONT $(cat /var/run/mysqld/mysqld.pid)

mysql> SHOW TABLE STATUS where Name = 'user'G
*************************** 1. row ***************************
           Name: user
         **Engine: MyISAM**
        Version: 10
     Row_format: Dynamic
           Rows: 27
 Avg_row_length: 91
    Data_length: 2476
Max_data_length: 281474976710655
   Index_length: 2048
      Data_free: 0
 Auto_increment: NULL
    Create_time: 2012-04-12 11:46:21
    Update_time: 2013-01-22 00:16:00
     Check_time: 2013-01-19 20:52:09
      Collation: utf8_bin
       Checksum: NULL
 Create_options:
        Comment: Users and global privileges
1 row in set (0.00 sec)

# mkdir /var/lib/mysql2/
# ln -s /var/lib/mysql/mysql /var/lib/mysql2/mysql

# /usr/sbin/mysqld --basedir=/usr
--datadir=/var/lib/mysql2
--plugin-dir=/usr/lib64/mysql/plugin
--user=mysql
--log-error=/var/lib/mysql2/server-64654.err
--pid-file=/var/lib/mysql2/server-64654.pid
--socket=/var/lib/mysql2/mysql.sock
--port=3307
--init-file=/var/cache/chef/grants.sql
--datadir=/var/lib/mysql2/

GRANT ALL ON *.* TO 'nagios-user'@'127.0.0.1' IDENTIFIED BY 'xxx' WITH GRANT OPTION;
FLUSH PRIVILEGES;

mysql --port=3307 -h 127.0.0.1 -e 'select User from mysql.user'
+-------------+
| User        |
+-------------+
| root |
| nagios_user |

mysql --port=3306 -h 127.0.0.1 -e 'select User from mysql.user'
+-------------+
| User        |
+-------------+
| root |

GRANT SELECT ON heartbeart.* to 'nagios-monitor'@'123.123.123.123'

INSERT INTO mysql.user SET
    user='nagios-monitor',
    host='123.123.123.123',
    password=PASSWORD('whateverpassword');
INSERT INTO mysql.db SET
    user='nagios-monitor',
    host='123.123.123.123',
    db='heartbeat',
    select_priv='Y';
FLUSH PRIVILEGES;

mysql> show grants for 'nagios-monitor'@'123.123.123.123';
+----------------------------------------------------------------------+
| Grants for nagios-monitor@123.123.123.123                            |
+----------------------------------------------------------------------+
| GRANT USAGE ON *.* TO 'nagios-monitor'@'123.123.123.123'             |
| GRANT SELECT ON `heartbeart`.* TO 'nagios-monitor'@'123.123.123.123' |
+----------------------------------------------------------------------+
2 rows in set (0.03 sec)

mysql>

INSERT INTO mysql.user SET
    user='nagios-monitor',
    host='123.123.123.123',
    password=PASSWORD('whateverpassword');
INSERT INTO mysql.tables_priv SET
    user='nagios-monitor',
    host='123.123.123.123',
    db='nagiosdb',
    grantor='root@localhost',
    table_priv='Select';
FLUSH PRIVILEGES;

mysql> show grants for 'nagios-monitor'@'123.123.123.123';
+------------------------------------------------------------------------------+
| Grants for nagios-monitor@123.123.123.133                                    |
+------------------------------------------------------------------------------+
| GRANT USAGE ON *.* TO 'nagios-monitor'@'123.123.123.123'                     |
| GRANT SELECT ON `nagiosdb`.`heartbeat` TO 'nagios-monitor'@'123.123.123.123' |
+------------------------------------------------------------------------------+
2 rows in set (0.00 sec)

mkdir /var/lib/mysql/mysql_schema
cd /var/lib/mysql/mysql_schema
cp /var/lib/mysql/mysql/* .
chown -R mysql:mysql /var/lib/mysql/mysql_schema

mkdir /var/lib/mysql/mysql_nagios
cd /var/lib/mysql/mysql_nagios
cp /var/lib/mysql/mysql/* .
chown -R mysql:mysql /var/lib/mysql/mysql_nagios

mkdir /var/lib/mysql/mysql_injection
chown -R mysql:mysql /var/lib/mysql/mysql_injection

INSERT INTO mysql_nagios.user SET
    user='nagios-monitor',
    host='123.123.123.123',
    password=PASSWORD('whateverpassword');
INSERT INTO mysql_nagios.tables_priv SET
    user='nagios-monitor',
    host='123.123.123.123',
    db='nagiosdb',
    grantor='root@localhost',
    table_priv='Select';

SET GLOBAL event_scheduler = 1;

rm -f /var/lib/mysql/mysql_injection/*
cp /var/lib/mysql/mysql_nagios/* /var/lib/mysql/mysql_injection/.

use mysql_injection
DELIMITER $$
CREATE EVENT ev_schema_inject
    ON SCHEDULE
      EVERY 1 MINUTE
      STARTS (NOW() + INTERVAL 1 MINUTE)
    DO
    BEGIN
        REPLACE INTO mysql.user SELECT * FROM mysql_injection.user;
        REPLACE INTO mysql.tables_priv SELECT * FROM mysql_injection.tables_priv;
        FLUSH PRIVILEGES;
    END $$
DELIMITER ;

DELETE FROM mysql.user;
DELETE FROM mysql.tables_priv;
INSERT INTO mysql.user SELECT * FROM mysql_orig.user;
INSERT INTO mysql.tables_priv SELECT * FROM mysql_orig.tables_priv;
FLUSH PRIVILEGES;
SET GLOBAL event_scheduler = 0;

# echo "select version()" | mysql -uroot
ERROR 1045 (28000): Access denied for user 'root'@'localhost' (using password: NO)

tbreak check_scramble
  commands
  silent
  return (long int)0
  end
  cont

# gdb -p $(cat /var/run/mysqld/mysqld.pid) -batch
    -x gdbscript

[New LWP 21273]
[New LWP 21272]
[Thread debugging using libthread_db enabled]
0x00007f6849d4a383 in poll () from /lib64/libc.so.6
Temporary breakpoint 1 at 0x660204: file /export/home/pb2/build/sb_0-26265460-1512805762.25/rpm/BUILD/mysql-5.6.39/mysql-5.6.39/sql/password.c, line 556.

# mysql -uroot -p123
Welcome to the MySQL monitor.  Commands end with ; or g.
Your MySQL connection id is 153
mysql>  UPDATE mysql.user SET Password=PASSWORD('SOMENEWPASSWORD') WHERE USER='root';
mysql>  flush privileges;

Temporary breakpoint 1 at 0x660204: file /export/home/pb2/build/sb_0-26265460-1512805762.25/rpm/BUILD/mysql-5.6.39/mysql-5.6.39/sql/password.c, line 556.
[Switching to Thread 0x7f68209f3700 (LWP 22242)]

[~]# echo "SELECT VERSION() | mysql -uroot -pSOMENEWPASSWORD
version()
5.6.39