help mariabackup command

Hi, I have mariadb 10.3.4-MariaDB, i trying to backup with mariabackup command. i setup binlog in my.cnf

#>cat /etc/my.cnf
log_bin = /mariadb_data01/binlog/mariadb-binlog
binlog_cache_size=100M
max_binlog_size=200M
expire_logs_days=4
binlog_format = mixed

And then, i trying to backup as below. after that backup has completed without any error.

#>mariabackup  --defaults-file="/etc/my.cnf" --backup --target-dir /mariadb_back/backup/  --user root --password xxxxx

i checked backup folder but binlog folder did not found.

and i check binnary logs either enable or disabled. it was good

MariaDB [(none)]> show binary logs;
+-----------------------+-----------+
| Log_name              | File_size |
+-----------------------+-----------+
| mariadb-binlog.000001 |       666 |
| mariadb-binlog.000002 |       370 |
| mariadb-binlog.000003 |       370 |
| mariadb-binlog.000004 |       523 |
| mariadb-binlog.000005 |       347 |
+-----------------------+-----------+
5 rows in set (0.000 sec)

and also check currnet binlog location. it was good.

#>ls -al /mariadb_data01/binlog/
-rw-rw---- 1 mysql mysql  666  Feb  8 17:37 mariadb-binlog.000001
-rw-rw---- 1 mysql mysql  370  Feb  8 17:39 mariadb-binlog.000002
-rw-rw---- 1 mysql mysql  370  Feb  9 10:00 mariadb-binlog.000003
-rw-rw---- 1 mysql mysql  523  Feb  9 10:09 mariadb-binlog.000004
-rw-rw---- 1 mysql mysql  370  Feb  9 12:37 mariadb-binlog.000005
-rw-rw---- 1 mysql mysql  347  Feb  9 12:37 mariadb-binlog.000006
-rw-rw---- 1 mysql mysql  270  Feb  9 12:37 mariadb-binlog.index

Qustion: Therefore, How can i backup binlog folder with mariabackup command?