/etc/logrotate.d/mysql postrotate script not work as expected because HOME variable not set

/etc/logrotate.d/mysql file:

1. The log file name and location can be set in

2. /etc/my.cnf by setting the "log-error" option

3. in either [mysqld] or [mysqld_safe] section as

4. follows:
   #

5. [mysqld]

6. log-error=/var/lib/mysql/mysqld.log
   #

7. In case the root user has a password, then you

8. have to create a /root/.my.cnf configuration file

9. with the following content:
   #

10. [mysqladmin]

11. password = <secret>

12. user= root
    #

13. where "<secret>" is the password.
    #

14. ATTENTION: The /root/.my.cnf file should be readable

15. ONLY by root !

/var/lib/mysql/mysqld.log {

1. create 600 mysql mysql
   notifempty
   daily
   rotate 5
   missingok
   compress
   postrotate

2. just if mysqld is really running
   if test -x /usr/bin/mysqladmin && \
   /usr/bin/mysqladmin ping &>/dev/null
   then
   /usr/bin/mysqladmin flush-logs
   fi
   endscript
   }

===================================

as result - logrotate service failed with error:

1. journalctl -u logrotate
   Apr 27 00:00:34 example.com systemd[1]: Starting Rotate log files...
   Apr 27 00:00:34 example.com logrotate[2184]: [52B blob data]
   Apr 27 00:00:34 example.com logrotate[2184]: error: 'Access denied for user 'root'@'localhost' (using password: NO)'
   Apr 27 00:00:34 example.com logrotate[2177]: error: error running shared postrotate script for '/var/log/mysqld.log
   Apr 27 00:00:34 example.com logrotate[2177]: /var/log/mysqld-slow.log
   Apr 27 00:00:34 example.com logrotate[2177]: '
   Apr 27 00:00:34 example.com systemd[1]: logrotate.service: Main process exited, code=exited, status=1/FAILURE
   Apr 27 00:00:34 example.com systemd[1]: logrotate.service: Failed with result 'exit-code'.
   Apr 27 00:00:34 example.com systemd[1]: Failed to start Rotate log files.
   Apr 28 00:00:34 example.com systemd[1]: Starting Rotate log files...
   Apr 28 00:00:34 example.com logrotate[2948]: [52B blob data]
   Apr 28 00:00:34 example.com logrotate[2948]: error: 'Access denied for user 'root'@'localhost' (using password: NO)'
   Apr 28 00:00:34 example.com logrotate[2943]: error: error running shared postrotate script for '/var/log/mysqld.log
   Apr 28 00:00:34 example.com logrotate[2943]: /var/log/mysqld-slow.log
   Apr 28 00:00:34 example.com logrotate[2943]: '
   Apr 28 00:00:34 example.com systemd[1]: logrotate.service: Main process exited, code=exited, status=1/FAILURE
   Apr 28 00:00:34 example.com systemd[1]: logrotate.service: Failed with result 'exit-code'.
   Apr 28 00:00:34 example.com systemd[1]: Failed to start Rotate log files.
   Apr 29 00:00:34 example.com systemd[1]: Starting Rotate log files...
   Apr 29 00:00:34 example.com logrotate[3708]: [52B blob data]
   Apr 29 00:00:34 example.com logrotate[3708]: error: 'Access denied for user 'root'@'localhost' (using password: NO)'
   Apr 29 00:00:34 example.com logrotate[3703]: error: error running shared postrotate script for '/var/log/mysqld.log
   Apr 29 00:00:34 example.com logrotate[3703]: /var/log/mysqld-slow.log
   Apr 29 00:00:34 example.com logrotate[3703]: '
   Apr 29 00:00:34 example.com systemd[1]: logrotate.service: Main process exited, code=exited, status=1/FAILURE
   Apr 29 00:00:34 example.com systemd[1]: logrotate.service: Failed with result 'exit-code'.
   Apr 29 00:00:34 example.com systemd[1]: Failed to start Rotate log files.

=========================================

file /root/.my.cnf exists and user and password is present:

/root/.my.cnf

[client]
user=root
password=******************

if run from root shell - command work fine, without errors:

/usr/bin/mysqladmin flush-logs ; echo $?
0

but from the logrotate this command does not work as expected.

strace executing /usr/bin/mysqladmin flush-logs from the logrotate service:

newfstatat(AT_FDCWD, "~/.my.cnf", 0x7ffcd1802560, 0) = -1 ENOENT (No such file or directory)

strace executing /usr/bin/mysqladmin flush-logs from the root shell:

newfstatat(AT_FDCWD, "/root/.my.cnf", {st_mode=S_IFREG|0644, st_size=42, ...}, 0) = 0

===================================

root cause of the bug:

in the normal mode env. variable

HOME=/root

present, but if executing /usr/bin/mysqladmin flush-logs from the logrotate service - env. variable HOME is absent, and /usr/bin/mysqladmin can't read /root/.my.cnf file and can't read password for connecting to database.

executing command

mysql -e 'FLUSH LOGS'

has the same bug as command

/usr/bin/mysqladmin flush-logs