This is how to fix root password on MySQL Galera clusters if the environment doesn't let you login with your old one.  In other words, if you're getting this:

ERROR 1045 (28000): Access denied for user 'root'@'mysql03.nix.mds.xyz' (using password: YES)

Do the following:

[root@mysql01 mysql]#
[root@mysql01 mysql]#systemctl set-environment MYSQLD_OPTS="–wsrep-new-cluster –skip-grant-tables"
[root@mysql01 mysql]#systemctl start mysqld
[root@mysql01 mysql]#mysql -u root -p
Enter password:
Welcome to the MySQL monitor.  Commands endwith ; or \g.
Your MySQL connection id is 20
Server version: 5.7.24-log MySQL Community Server – (GPL), wsrep_25.16

Copyright (c) 2000, 2018, 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> 
mysql> UPDATE mysql.user SET password=password("MYSECRET") WHERE user='root';
ERROR 1054 (42S22): Unknown column 'password' in 'field list'
mysql> SET PASSWORD FOR 'root'@'localhost' = PASSWORD('MYSECRET');
ERROR 1290 (HY000): The MySQL server is running with the –skip-grant-tables option so it cannot execute this statement
mysql>
mysql>
mysql> update mysql.user set authentication_string=password('MYSECRET') where user='root';
Query OK, 1 row affected, 1 warning (0.03 sec)
Rows matched: 1  Changed: 1  Warnings: 1

mysql> show grants;
ERROR 1290 (HY000): The MySQL server is running with the –skip-grant-tables option so it cannot execute this statement
mysql> 
mysql> flush privileges;
Query OK, 0 rows affected (0.03 sec)

mysql>
mysql> show grants;
ERROR 1141 (42000): There is no such grant defined for user 'skip-grants user' on host 'skip-grants host'
mysql> flush privileges;
Query OK, 0 rows affected (0.01 sec)

mysql> show grants;
ERROR 1141 (42000): There is no such grant defined for user 'skip-grants user' on host 'skip-grants host'
mysql> quit
Bye

Test it out and alter the database once more:

 
[root@mysql01 mysql]# mysql -uroot -pMYSECRET -e'show grants'
mysqlPlease use –connect-expired-password option or
: [Warning] Using a password on the command line interface can be insecure.invokemysql in interactive mode.
[root@mysql01 mysql]#mysql –uroot -p –e'show grants'
Enter password:
Please use –connect-expired-password option or invokemysql in interactive mode.
[root@mysql01 mysql]#mysql -u root -p
Enter password:
Welcome to the MySQL monitor.  Commands endwith ; or \g.
Your MySQL connection id is 712
Server version: 5.7.24-log 

Copyright (c) 2000, 2018, 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 grants;
ERROR 1820 (HY000): You must reset your password usingALTER USER statement before executing this statement.
mysql> ALTER USER 'root'@'localhost' IDENTIFIED BY 'MYSECRET';
Query OK, 0 rows affected (0.01 sec)

mysql> flush privileges;
Query OK, 0 rows affected (0.01 sec)

mysql> quit

Bye

Test the full access:

[root@mysql01 mysql]# cat /usr/bin/mysqld_bootstrap
# Copyright (c) 2016, Codership Oy. All rights reserved.
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; version 2 of the License.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301USA

#
# Awsrep-enabled MySQL server daemon needs a special option if it is to start
# as the first node of a Galera cluster.
# With SystemV init, this could be passed as a "bootstrap" (rather than "start") command:
#     sudo servicemysqld bootstrap
#
# Withsystemd, such alternative commands are not possible.
# However,systemd passes a set of environment variables to the service process
# it starts, and this set can be modified.
# Such a modification would be persistent, so it must be undone after use.
#
# If other options are set already, make sure to use them, and to restore them.

OLDVAL=$(systemctl show-environment | grep '^MYSQLD_OPTS=')

if [ -z “$OLDVAL” ]; then
    systemctl set-environment   MYSQLD_OPTS="–wsrep-new-cluster"
    systemctl start             mysqld
    systemctl unset-environment MYSQLD_OPTS
else
   systemctl set-environment   "$OLDVAL —wsrep-new-cluster"
   systemctl start             mysqld
   systemctl set-environment   "$OLDVAL"
fi

[root@mysql01 mysql]# systemctl unset-environment MYSQLD_OPTS
[root@mysql01 mysql]# /usr/bin/mysqld_bootstrap

[root@mysql01 mysql]# mysql -u root -p
Enter password:
Welcome to the MySQL monitor.  Commands endwith ; or \g.
Your MySQL connection id is 29
Server version: 5.7.24-log MySQL Community Server – (GPL), wsrep_25.16

Copyright (c) 2000, 2018, 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>

You may still run into issues.  This is how to resolve this particular one:

mysql>
mysql> ALTER USER 'root'@'localhost' IDENTIFIED BY '<PASS>';
ERROR 1396 (HY000): Operation ALTER USER failed for 'root'@'localhost'
mysql> flush privileges;
Query OK, 0 rows affected (0.01 sec)

mysql> ALTER USER 'root'@'localhost' IDENTIFIED BY '<PASS>'
    -> ;
ERROR 1396 (HY000): Operation ALTER USER failed for 'root'@'localhost'
mysql> FLUSH PRIVILEGES;
Query OK, 0 rows affected (0.01 sec)

mysql>
mysql>
mysql> ALTER USER 'root'@'localhost' IDENTIFIED BY '<PASS>'
    -> ;
ERROR 1396 (HY000): Operation ALTER USER failed for 'root'@'localhost'
mysql> create user 'root'@'localhost' identified by 'john123';
Query OK, 0 rows affected (0.01 sec)

mysql> create user 'root'@'localhost' identified by '<PASS>';
ERROR 1396 (HY000): Operation CREATE USER failed for 'root'@'localhost'
mysql> alter user 'root'@'localhost' identified by '<PASS>';
Query OK, 0 rows affected (0.00 sec)

mysql>

 

REF: https://bugs.mysql.com/bug.php?id=79027

Cheers,
TK